path: root/open_issues/time.mdwn

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[[!tag open_issue_porting]]

[[!toc]]


# `time`

Neither the `time` executable from the GNU time package work completely
correctly, nor does the GNU Bash built-in one.

    tschwinge@flubber:~ $ \time sleep 2
    0.00user 0.00system 9:38:00elapsed 0%CPU (0avgtext+0avgdata 0maxresident)k
    0inputs+0outputs (0major+0minor)pagefaults 0swaps
    tschwinge@flubber:~ $ \time sleep 4
    0.00user 0.00system 18:50:25elapsed 0%CPU (0avgtext+0avgdata 0maxresident)k
    0inputs+0outputs (0major+0minor)pagefaults 0swaps
    tschwinge@flubber:~ $ \time sleep 6
    0.00user 0.00system 28:00:53elapsed 0%CPU (0avgtext+0avgdata 0maxresident)k
    0inputs+0outputs (0major+0minor)pagefaults 0swaps
    tschwinge@flubber:~ $ time sleep 2
    
    real    0m2.093s
    user    0m0.000s
    sys     0m0.011s
    tschwinge@flubber:~ $ time sleep 4
    
    real    0m4.083s
    user    0m0.000s
    sys     0m0.010s
    tschwinge@flubber:~ $ time sleep 6
    
    real    0m6.164s
    user    0m0.000s
    sys     0m0.010s

GNU time's *elapsed* value is off by some factor.

    $ \time factor 1111111111111111111
    1111111111111111111: 1111111111111111111
    0.00user 0.00system 52:39:24elapsed 0%CPU (0avgtext+0avgdata 0maxresident)k
    0inputs+0outputs (0major+0minor)pagefaults 0swaps
    $ time factor 1111111111111111111
    1111111111111111111: 1111111111111111111
    
    real    0m11.424s
    user    0m0.000s
    sys     0m0.010s

As above; also here all the running time should be attributed to *user* time.
This is probably a [[!taglink open_issue_gnumach]].


## 2011-09-02

Might want to revisit this, and take Xen [[!tag open_issue_xen]] into account
-- I believe flubber has already been Xenified at that time.


### IRC, freenode, #hurd, 2011-09-02

While testing some [[performance/IPC_virtual_copy]] performance issues:

    <tschwinge> And I can confirm that with dd if=/dev/zero of=/dev/null bs=4k
      running, a parallel sleep 10 takes about 20 s (on strauss).

## 2013-03-30/31

Investigating time's `configure`, a difference of the output between Linux and
Hurd shows:

    -checking for wait3 that fills in rusage... yes
    +checking for wait3 that fills in rusage... no

This causes a different code path in `resuse.c` to be used; such code path does
not get a define for `HZ`, which is then defined with a fallback value of 60.

[[!debbug 704283]] has been filed with a fix for this no-wait3 case.


# `times`

## guile

### IRC, freenode, #hurd, 2013-08-21

    <nalaginrut> does guile2 on hurd fixed? times issue
    <teythoon> nalaginrut: does not look good
    <teythoon> scheme@(guile-user)> (times)
    <teythoon> $1 = #(0 0 0 0 0)
    <nalaginrut> well, seems not a fixed version, if there's fixed version
    <nalaginrut> since it's not Guile's bug, I can do nothing for it
    <teythoon> ah
    <nalaginrut> in spite of this, Guile2 works I think
    <nalaginrut> all tests passed but 2 fail
    <nalaginrut> one of the failure is version shows "UNKNOWN" which is
      trivials
    <teythoon> well, did you try to fix the times issue in Hurd?
    <nalaginrut> I didn't , I have to get more familiar with hurd first
    <nalaginrut> I'm playing hurd these days
    <teythoon> :)
    <nalaginrut> anyway, I think times issue is beyond my ability at present
    <nalaginrut> ;-P
    <teythoon> times is implemented in the glibc, in sysdeps/mach/hurd/times.c
    <teythoon> don't say that before you had a look
    <nalaginrut> yes, you're right
    <nalaginrut> but I think times has something to do with the kernel time
      mechanism, dunno if it's related to the issue
    <nalaginrut> how did you get the times.c under hurd?
    <nalaginrut> apt-get source glibc?
    <teythoon> well, I'd clone git://sourceware.org/git/glibc.git
    <teythoon> and yes, the kernel is involved
    <teythoon> task_info is used to obtain the actual values
    <teythoon>
      http://www.gnu.org/software/hurd/gnumach-doc/Task-Information.html
    <teythoon> I'd guess that something fails, but the times(2) interface is
      not able to communicate the exact failure
    <nalaginrut> maybe it's not proper to get src from upstream git? since it's
      OK under Linux which uses it too
    <nalaginrut> but apt-get source glibc has nothing
    <teythoon> so I would copy the times(2) implementation from the libc so
      that you can modify it and run it as a standalone program
    <teythoon> well, the libc has system dependent stuff, times(2) on Linux is
      different from the Hurd version
    <teythoon> it has to be
    <nalaginrut> alright, I got what you mean ;-)
    <teythoon> and the debian libc is built from the eglibc sources, so the
      source package is called eglibc iirc
    <nalaginrut> ah~I'll try
    <teythoon> have you tried to rpctrace your times test program? the small c
      snippet you posted the other day?
    <nalaginrut> I haven't build all the tools & debug environment on my hurd
      ;-(
    <teythoon> what tools?
    <nalaginrut> well, I don't even have git on it, and I'm installing but
      speed is slow, I'm looking for a new mirror
    <teythoon> ah well, no need to do all this on the Hurd directly
    <teythoon> building the libc takes like ages anyway
    <nalaginrut> oops ;-)
    <nalaginrut> I'll take your advice to concentrate on times.c only
    <teythoon> oh well, it might be difficult after all, not sure though
    <teythoon> times sends two task_info messages, once with TASK_BASIC_INFO,
      once with TASK_THREAD_TIMES_INFO
    <teythoon> here is the relevant rpctrace of your test program:
    <teythoon> task131(pid14726)->task_info (1 10) = 0 {0 25 153427968 643072 0
      0 0 0 1377065590 570000}
    <teythoon> task131(pid14726)->task_info (3 4) = 0 {0 0 0 10000}
    <teythoon> ok, I don't know enough about that to be honest, but
      TASK_THREAD_TIMES_INFO behaves funny
    <teythoon> I put a sleep(1) into your test program, and if I rpctrace it,
      it behaves differently o_O
    * nalaginrut is reading task-information page to get what it could be
    <nalaginrut> maybe I have to do the same steps under Linux to find some
      clue
    <teythoon> no, this is Mach specific, there is no such thing on Linux
    <teythoon> on Linux, times(2) is a system call
    <teythoon> on Hurd, times is a function implemented in the libc that
      behaves roughly the same way
    <nalaginrut> OK~so different
    <teythoon> look at struct task_basic_info and struct task_thread_times_info
      in the task-information page for the meaning of the values in the
      rpctrace
    <teythoon> yes, very
    <braunr> nalaginrut: you may want to try a patch i did but which is still
      waiting to be merged in glibc
    <nalaginrut> braunr:  ah~thanks for did it ;-)
    <nalaginrut> can I have the link?
    <braunr> i'm getting it
    <braunr> teythoon: funny things happen with rpctrace, that's expected
    <braunr> keep in mind rpctrace doesn't behave like ptrace at all
    <braunr> it acts as a proxy
    <braunr> nalaginrut:
      http://git.savannah.gnu.org/cgit/hurd/glibc.git/commit/?h=rbraun/getclktck_100_hz&id=90404d6d1aa01f6ce1557841f5a675bb6a30f508
    <braunr> nalaginrut: you need to add it to the debian eglibc patch list,
      rebuild the packages, and install the resulting .debs
    <braunr> if you have trouble doing it, i'll make packages when i have time
    <nalaginrut> braunr:  I think your test result is expected? ;-)
    <braunr> what test result ?
    <nalaginrut> times test under that patch
    <braunr> yes
    <braunr> but i have no idea if it will work
    <braunr> my patch fixes a mismatch between glibc and the procfs server
    <braunr> nothing more
    <braunr> it may help, it may not, that's what i'd like to know
    <nalaginrut> hah~thanks for that
    <nalaginrut> I get source from apt-get, then manually modified the files,
      no much code ;-)
    <nalaginrut> compiling
    <nalaginrut> there is no cpuinfo in /proc?
    <teythoon> no
    <nalaginrut> a feature need to be done? or there's another way for that?
    <teythoon> well, it hasn't been implemented
    <teythoon> do you need that? what for?
    <nalaginrut> compiling error, I realized I should use gcc-4.7
    <pinotree> how are you building?
    <nalaginrut> I just happened to play proc while compiling, and found
      there's no
    <nalaginrut> cxa_finalize.c:48:1: error: ‘tcbhead_t’ has no member
      named ‘multiple_threads’
    <nalaginrut> I changed to gcc-4.7
    <pinotree> just edit the sources, and then dpkg-buildpackage -nc -us -uc
    <pinotree> that will rebuild the debian package as it would be in a debian
      build, making sure all the build dependencies are there, etc
    <pinotree> doing it different than that is just wrong™
    <nalaginrut> ok, doing
    <pinotree> were you really doing ./configure etc yourself?
    <nalaginrut> well, I can't wait till it's done, I'll let it compile and
      check it out tomorrow
    <nalaginrut> I used configure, yes ;-P
    <pinotree> not good
    <nalaginrut> I have to go, thanks for help guys


### IRC, freenode, #hurd, 2013-08-22

    < nalaginrut> eglibc was done by dpkg-buildpackage, then how to install it?
      (sorry I'm a brand new debian users)
    < nalaginrut> oh~I found it
    < nalaginrut> yes, (times) returns reasonable result ;-)
     * nalaginrut is trying 'make check'
    < nalaginrut> unfortunately, it can't pass the test though, I'm researching
      it, anyway, we made first step
    < nalaginrut> for Hurd internal-time-units-per-second will be 1000
    < nalaginrut> , but the elapsed time is far larger than (* 2
      internal-time-units-per-second)
    < nalaginrut> I think the different of two returned clocks after 1 second
      should be the TIME_UNITS_PER_SECOND, in principle
    < nalaginrut> but I'm not sure if it's elibc or Guile bug
    < nalaginrut> dunno, maybe clock tick should be 1000?
    < nalaginrut> well, I'll try clock per second as 1000
    < braunr> nalaginrut: clock tick (or actually, the obsolete notion of a
      clock tick in userspace) should be 100
    < braunr> nalaginrut: how did you come with 1000 ?
    < nalaginrut> braunr:  Guile set TIME_UNITS_PER_SECOND to 1000 when there's
      no 8bytes size and doesn't define HAVE_CLOCK_GETTIME
    < nalaginrut> #if SCM_SIZEOF_LONG >= 8 && defined HAVE_CLOCK_GETTIME
    < nalaginrut> #define TIME_UNITS_PER_SECOND 1000000000
    < nalaginrut> #else
    < nalaginrut> #define TIME_UNITS_PER_SECOND 1000
    < nalaginrut> #endif
    < nalaginrut> and the test for 'times' used time-units-per-second
    < pinotree> what has sizeof(long) have to do with time units per second?
    < nalaginrut> dunno, maybe the representation of time?
    < nalaginrut> the test failed since the difference between two clocks after
      1sec is too large
    < nalaginrut> and for the test context, it should small than 2 times of
      units-per-second
    < nalaginrut> should be smaller 
    < nalaginrut> sorry for bad English
    < pinotree> aren't you basically looking for clock_getres?
    < nalaginrut> pinotree:  I don't understand what you mean
    < pinotree>
      http://pubs.opengroup.org/onlinepubs/9699919799/functions/clock_getres.html
    < nalaginrut> I wonder if there's a standard CLK_PER_SEC for Hurd
    < nalaginrut> or it can be modified as wish
    < pinotree> why do you need it?
    < nalaginrut> the difference is 10,000,000, which can never less than
      2*clock_per_second
    < nalaginrut> pinotree:  I don't need it, but I want to know if there's a
      standard value
    < braunr> nalaginrut: ok so, this is entirely a guile thing
    < braunr> nalaginrut: did you test with my patch ?
    < nalaginrut> braunr:  yes, 'times' works fine
    < braunr> but even with that, a tets fails ?
    < braunr> test*
    < nalaginrut> well, I can't say works fine, the proper description is "now
      it has reasonable result"
    < braunr> youpi: could you bring
      http://git.sceen.net/hurd/glibc.git/commit/?id=90404d6d1aa01f6ce1557841f5a675bb6a30f508
      into debian glibc btw ?
    < nalaginrut> braunr:  it failed the test since the clock run too fast, but
      it should be smaller than 2*clk-per-sec
    < braunr> i don't get that
    < braunr> can you show the code that checks the condition ?
    < nalaginrut> braunr:  http://pastebin.com/sG3QxnPt
    < braunr> * 0.5 internal-time-units-per-second ?
    < nalaginrut> for C users, it's just like
      a=times(...);sleep(1);b=times(...); then time-units-per-sec/2 <= (b-a) <=
      time-units-per-sec*2
    < braunr> ah ok
    < nalaginrut> the test passes when it's true
    < braunr> so basically, it says sleep(1) sleeps for more than 2 seconds
    < braunr> can you check the actual value ?
    < braunr> b-a
    < nalaginrut> hold on for minutes
    < nalaginrut> it's 10,000,000
    < nalaginrut> for clk-per-sec=1000,000,000, it's OK
    < nalaginrut> but for 100 or 1000, it's too small
    < braunr> let's forget 100
    < braunr> guile uses 1000
    < nalaginrut> OK
    < braunr> but i still don't get why
    < nalaginrut> so I asked if there's standard value, or it can be ajustified
    < nalaginrut> adjusted
    < braunr> ok so, times are expressed in clock ticks
    < braunr> are you sure you're using a patched glibc ?
    < nalaginrut> yes I used your patch, and the 'times' get reasonable result
    < braunr> then
    < braunr> 11:28 < nalaginrut> it's 10,000,000
    < braunr> doesn't make sense
    < nalaginrut> hmm
    < braunr> anhd i don't understand the test
    < braunr> what's tms:clock new ?
    < nalaginrut> it's actually the return value of 'times'
    < nalaginrut> Guile wrap the clock_t and tms to a vector, then we can get
      all the thing in a row
    < nalaginrut> 'new' is a variable which was gotten after 1 sec
    < braunr> let's see what this does exactly
    < nalaginrut> equal to "new = times(...)"
    < nalaginrut> 'tms' equal to (clock_t (struct tms))
    < nalaginrut> we have to pass in the struct pointer to get the struct
      values filled, but for Guile we don't use pointer, times actually returns
      two things: clock_t and struct tms
    < nalaginrut> and Guile returns them as a vector in a row, that's it
    < braunr> nalaginrut: test this please:
      http://darnassus.sceen.net/~rbraun/test.c
    < braunr> i don't have a patched libc here
    < braunr> i'll build one right now
    < nalaginrut> clock ticks: 1000000
    < braunr> and this seems reasonable to you ?
    < braunr> anyway, i think the guile test is bugged
    < nalaginrut> no, the reasonable is not for this
    < braunr> does it ever get the clock tick value from sysconf() ?
    < nalaginrut> I say reasonable since it's always 0 both for clock and tms,
      before apply your patch
    < braunr> uh no
    < braunr> i have the same value, without my patch
    < nalaginrut> so I said "I can't say it works fine"
    < braunr> either the test is wrong because it doesn't use sysconf()
    < nalaginrut> anyway, I don't think times should return "all zero"
    < braunr> or the clock values have already been ocnverted
    < braunr> but it doesn't
    < braunr> you did something wrong
    < nalaginrut> with your patch it doesn't 
    < braunr> without neither
    < braunr> 11:43 < braunr> i have the same value, without my patch
    < nalaginrut> well, it's too strange
    < braunr> check how the test actually gets the clock values
    < braunr> also, are your running in vbox ?
    < braunr> you*
    < nalaginrut> no ,it's physical machine
    < braunr> oh
    < braunr> nice
    < braunr> note that vbox has timing issues
    < nalaginrut> I thought I should give you some info of CPU, but there's no
      /proc/cpuinfo
    < braunr> shouldn't be needed
    < nalaginrut> OK
    < braunr> run my test again with an unpatched glibc
    < braunr> just to make sure it produces the same result
    < braunr> and
    < nalaginrut> so the clock-per-sec is machine independent for Hurd I think
    < braunr> 11:46 < braunr> check how the test actually gets the clock values
    < nalaginrut> since it's implemented in userland
    < braunr> clock-per-sec is always system dependent
    < braunr>        All times reported are in clock ticks.
    < braunr>        The number of clock ticks per second can be obtained
      using:
    < braunr>            sysconf(_SC_CLK_TCK);
    < braunr> 11:46 < braunr> check how the test actually gets the clock values
    < braunr> to see if they're converted before reaching the test code or not
     * nalaginrut is building eglibc 
    < braunr> building ?
    < braunr> what for ?
    < nalaginrut> I modified it to 1000, now it's useless
    < braunr> we want it to 100 either way
    < nalaginrut> and how to reinstall eglibc under debian?
    < braunr> it's obsolete, procfs already uses 100, and 100 is low enough to
      avoid overflows in practically all cases
    < braunr> aptitude install libc0.3=<version>
    < nalaginrut> OK
    < braunr> aptitude show -v libc0.3
    < braunr> for the list of available versions
    < nalaginrut> out of topic, what's the meaning of the code in
      quantize_timeval ?
    < nalaginrut> tv->tv_usec = ((tv->tv_usec + (quantum - 1)) / quantum) *
      quantum;
    < nalaginrut> I can't understand this line
    < braunr> scaling and rounding i guess
    < nalaginrut> hmm...but quantum seems always set to 1?
    < nalaginrut> 100/__getclktck()
    < braunr> ah right
    < braunr> old crap from the past
    < nalaginrut> and clk-tck is 100
    < braunr> the author probably anticipated clk_ticks could vary
    < braunr> in practice it doesn't, and that's why it's been made obsolete
    < nalaginrut> I wonder if it could be vary
    < braunr> no
    < nalaginrut> alright
    < nalaginrut> why not just assign it to 1?
    < braunr> 11:55 < braunr> old crap from the past
    < braunr> the hurd is 20 years old
    < braunr> like linux
    < nalaginrut> oh~
    < braunr> but with a lot less maintenance
    < nalaginrut> braunr:  well, I tried the original eglibc, your test was
      clock ticks: 1000000
    < nalaginrut> but in Guile, (times) ==> (0 0 0 0 0)
    < nalaginrut> the reasonable result maybe: #(4491527510000000 80000000 0 0
      0)
    < braunr> 11:46 < braunr> check how the test actually gets the clock values
    < braunr> ah, he left


### IRC, freenode, #hurd, 2013-08-23

    < braunr> nalaginrut: times() doesn't seem to be affected by my patch at
      all
    < nalaginrut> braunr:  but it did in my machine
    < nalaginrut> well, I think you mean it doesn't affect your C test code
    < braunr> i'm almost sure something was wrong in your test
    < braunr> keep using the official debian glibc package
    < nalaginrut> I don't think it's test issue, since every time (times)
      return zero, the test can never get correct result
    < braunr> times doesn't return 0
    < braunr> for sleep(1), i always have the right result, except in
      microseconds
    < nalaginrut> times in Guile always return #(0 0 0 0 0)
    < braunr> (microseconds is the native mach time unit)
    < braunr> well, guile does something wrong
    < nalaginrut> after sleep 1, it's 0 again, so it's none sense
    < braunr> 11:46 < braunr> check how the test actually gets the clock values
    < braunr> not on my system
    < nalaginrut> but (times) returns reasonable result after applied your
      patch 
    < braunr> that's not normal, since times isn't affected by my patch
    < nalaginrut> oops
    < braunr> you need to look for what happens in guile between the times()
      call and the #(0 0 0 0 0) values
    < nalaginrut> well, I tried many times between patch or non-patch, I think
      there's no mistake
    < nalaginrut> I read the 'times' code in Guile, there's nothing strange,
      just call 'times' and put all the result to a vector
    < braunr> which means there is no conversion
    < braunr> in which case the test is plain wrong since there MUST also be a
      call to sysconf()
    < braunr> to obtain the right clock ticks value
    < braunr> is your box reachable with ssh ?
    < nalaginrut> oh~wait, seems there's a quotient operation, I'm checking
    < nalaginrut> factor = scm_quotient (scm_from_long (TIME_UNITS_PER_SECOND),
    < nalaginrut>                        scm_from_long (ticks_per_second));
    < braunr> iirc, TIME_UNITS_PER_SECOND is hardcoded
    < nalaginrut> unless factor is zero
    < nalaginrut> yes, it's hardcoded
    < braunr> that's completely non portable and wrong
    < nalaginrut> you suggest to call sysconf?
    < braunr> yes
    < braunr> but i don't have the code in mind
    < braunr> what is ticks_per_second ?
    < nalaginrut> OK, that's one issue, we have to find why times return 0
    < braunr> 14:14 < braunr> is your box reachable with ssh ?
    < braunr> i'd like to make sure times returns 0 at your side
    < braunr> because it doesn't at mine
    < nalaginrut> no
    < braunr> until i can reproduce, i can't consider there is a problem
    < nalaginrut> I think it's unreachable for outer space
    < nalaginrut> well, if you want to reproduce, just get guile src of debian
    < braunr> guile 2.0 ?
    < nalaginrut> yes, apt-get source guile-2.0
    < nalaginrut> I'm checking ticks_per_second
    < braunr> got the source, how do i test 
    < braunr> ?
    < nalaginrut> you have to build it, and run ./meta/guile, then you don't
      have to install it
    < nalaginrut> and try (times)
    < braunr> aw libgc
    < nalaginrut> the reasonable result should be #(4313401920000000 110000000
      20000000 0 0) or something alike
    < nalaginrut> but #(0 0 0 0 0) in each time is not reasonable apparently
    < nalaginrut> maybe you need apt-get build-dep guile-2.0?
    < braunr> already done
    < nalaginrut> building Guile2 may take very long time
    < nalaginrut> about 30 minutes in my old machine
    < braunr> then it should take just a few minutes on mine
    < nalaginrut> alright it's not very long, I've spent 8 hours for gcc in LFS
    < braunr> 8 hours ?
    < braunr> takes 5-10 minutes on a common machine ..
    < nalaginrut> but it's Celeron566 at that time...
    < braunr> ah, that old
    < nalaginrut> include bootstrap, so very long
    < braunr> nalaginrut: i got the test failure from the build procedure, how
      do i run it manually ?
    < nalaginrut> braunr:   ./meta/guile -L test-suite
      test-suite/tests/time.test
    < nalaginrut> braunr:  or make check for all
    < braunr> put a print after the schedule() and before the return nil; in
      runtime_mstart, since that's the body of new threads
    < nlightnfotis> unfortunately, I can't confirm this with goroutines
      running; the assertion failure aborts before I can get anything useful
    < braunr> you can
    < braunr> make sure there is a \n in the message, since stdout is line
      buffered by default
    < braunr> if you don't reach that code, it means threads don't exit
    < braunr> at least goroutine threads
    < braunr> btw, where is the main thread running ?
    < nlightnfotis> I just checked there is a \n at the end.
    < nlightnfotis> "<braunr> btw, where is the main thread running " could you
      elaborate a little bit on this?
    < braunr> what does main() after initializing the runtime ?
    < braunr> +do
    < nlightnfotis> the runtime main or the process's main?
    < braunr> the process
    < braunr> nlightnfotis: what we're interested in is knowing whether main()
      exits or not
    < nlightnfotis> braunr: I can see there are about 4 functions of interest:
      runtime_main (the main goroutine, and I can imagine 1st thread)
    < nlightnfotis> main_init (I don't know what it does, will check this out
      now)
    < nlightnfotis> main_main (not sure about this one either)
    < nlightnfotis> and runtime_exit (0)
    < braunr> i can see that too
    < braunr> i'm asking about main()
    < nlightnfotis> which seems to be the function that terminates the main
      thread
    < nlightnfotis> <braunr> nlightnfotis: what we're interested in is knowing
      whether main() exits or not --> my theory is runtime_exit (0) exits the
      process' main. Seeing as at various times go programs echo $? == 0.
    < nlightnfotis> let me research that a little bit
    < nlightnfotis> braunr: that will require a bit more studying. main_main()
      and main_init() are both expanded to assembly tags if I understand it
      correctly. 
    < nlightnfotis> main.main and __go_init_main respectively.
    < braunr> why are you looking from there instead of looking from main() ?
    < nlightnfotis> are we not looking out if main exits?
    < braunr> we are
    < braunr> so why look at main_main ?
    < braunr> or anything else than main ?
    < nlightnfotis> these are called inside runtime_main and I figured out they
      might have a clue
    < braunr> runtime_main != main
    < braunr> (except if there is aliasing)
    < nlightnfotis> there is still the possibility that runtime_main is the
      main function and that runtime_exit(0) exits it.
    < braunr> there is no doubt that main is main
    < braunr> (almost)
    < nlightnfotis> and I just found out that there is no main in assembly
      produced from go. Only main.main
    < braunr> check the elf headers for the entry point then
    < nlightnfotis> braunr: I went through the headers, and found the process'
      main. You can find it in <gcc_root>/libgo/runtime/go-main.c
    < nlightnfotis> it seems very strange though: It creates a new thread, then
      aborts?
    < braunr> nlightnfotis: see :)
    < braunr> nlightnfotis: add traces there
    < nlightnfotis> braunr: can you look into that piece of code to check out
      something I don't understand?
    < nlightnfotis> braunr: I can not seem able to find __go_go 's definition
    < nlightnfotis> only a declaration in runtime.h
    < braunr>
      https://github.com/NlightNFotis/gcc/blob/master/libgo/runtime/proc.c,
      line 1552
    < nlightnfotis> gee thanx. For a strange kind of fashion, I was looking for
      it in runtime.c
    < braunr> use git grep
    < braunr> or tags/cscope
    < nlightnfotis> braunr: yep! runtime_exit does seem to terminate a go
      process that was not otherwise abnormally terminated.
    < braunr> ?
    < braunr> is it called or not ?
    < braunr> runtime_exit is a macro on exit()
    < braunr> so we already know what it does
    < nlightnfotis> it is called
    < braunr> ok
    < braunr> that's not normal :)
    < nlightnfotis> for a simple program
    < braunr> uh ?
    < nlightnfotis> for one that has a go routine
    < braunr> but
    < nlightnfotis> it doesn't
    < nlightnfotis> it's expected
    < braunr> ok
    < braunr> that makes sense
    < braunr> well, trace
    < braunr> keep tracing
    < braunr> for example in main()
    < braunr> is runtime_mstart() actually reached ?
    < nlightnfotis> yeah main and runtime_main were my next two targets
    < braunr> good
    < nlightnfotis> and now I followed your advice and it does compiler much
      faster
    < braunr> so, it looks like the main thread just becomes a mere kernel
      thread
    < braunr> running runtime_mstart() and fetching goroutines as needed
    < braunr> after your traces, i'd suggest running a small go test program,
      with one simple goroutine (doesn't crash right ?)
    < braunr> and trace context switching
    < braunr> but after the traces
    < braunr> one important trace is to understand why runtime_exit gets called
    < nlightnfotis> it does crash even with 1 goroutine
    < braunr> oh
    < braunr> when doesn't it crash ?
    < nlightnfotis> when it has 0 goroutines
    < nlightnfotis> it works as expected
    < nlightnfotis> but anything involving goroutines crashes
    < nlightnfotis> and goroutines are very important; everything in the
      standard library involves goroutines
    < braunr> ok
    < braunr> doesn't change what i suggested, good
    < braunr> 1/ find out why runtime_exit gets called
    < braunr> 2/ trace context switching with 1 goroutine
    < nlightnfotis> on it.
    < braunr> in all cases, make all your goroutines (including the main one)
      *not* return
    < braunr> so that you don't deal with goroutine destruction yet
    < nlightnfotis> runtime_mstart in main doesn't to be run at all. So the
      path is __go_go and then return from it.
    < nlightnfotis> *doesn't seem


### IRC, freenode, #hurd, 2013-08-26

    < braunr> youpi: my glibc clock patch looks incomplete btw
    < youpi> which one?
    < youpi> ah, the ticks one?
    < braunr> yes
    < braunr> it doesn't change the values returned by times
    < braunr> as a side effect, the load average bumps to 2+ on an idle machine


### IRC, freenode, #hurd, 2013-08-27

    < nalaginrut> braunr:  have you tried Guile2 on your machine? ;-)
    < braunr> nalaginrut: no
    < braunr> nalaginrut: but i saw the code actually does use sysconf()
    < nalaginrut> braunr:  yes, for ticks_per_second
    < braunr> i had to look myself to find it out, you didn't say it, despite
      me asking multiple times
    < braunr> it won't make debugging easier ;p
    < braunr> nalaginrut: also, the return value of times is actually *never*
      used
    < braunr> i don't know why you've been talking about it so much
    < nalaginrut> braunr:  I'm sorry, it's first time to look stime.c for me
    < braunr> the interesting function is get_internal_run_time_times()
    < nalaginrut> what do you mean about "the return value of times is actually
      *never* used"? in which context?
    < braunr> see get_internal_run_time_times
    < braunr> struct tms time_buffer;
    < braunr> times(&time_buffer);
    < braunr> return ...
    < braunr> and yes, the user and system time reported in struct tms are 0
    < braunr> let's see what posix has to say about it
    < pinotree> it says it will return (clock_t)-1 for errors, but no standard
      errors are defined yet
    < nalaginrut> but I don't think  get_internal_run_time_times has something
      to do with scm_times
    < braunr> well, i don't see any other call to times()
    < braunr> i've asked you repeatedly to look for how guile fetches the data
    < braunr> i think it's done in get_internal_run_time_times
    < braunr> what makes you think otherwise ?
    < braunr> our times() seems to behave fine, other than the units of the
      return value
    < nalaginrut> I don't understand what do you mean?
      get_internal_run_time_times is unrelated to scm_times which is actually
      "times" in Scheme code
    < braunr> ok
    < nalaginrut> I think we're talking about "times" activity, right?
    < braunr> ok so result is a vector
    < braunr> with the return value and the four values in struct tms
    < nalaginrut> yes
    < braunr> and what looks interesting is
    < braunr> factor = scm_quotient (scm_from_long (TIME_UNITS_PER_SECOND),
      scm_from_long (ticks_per_second));
    < braunr> SCM_SIMPLE_VECTOR_SET (result, 0, scm_product (scm_from_long
      (rv), factor));
    < braunr> TIME_UNITS_PER_SECOND is 1000
    < nalaginrut> yes, it means (clock_t *
      (TIME_UNITS_PER_SECOND/ticks_per_second)), though I've no idea why it
      does this
    < braunr> normalizing values i guess
    < nalaginrut> I wonder if the factor should be 1, just guessing
    < braunr> let's see what our clock tick really is
    < braunr> 1000000 on an unmodified libc
    < braunr> 100 with my patch
    < nalaginrut> so what's the problem?
    < nalaginrut> all the values were multiplied by ticks, it's fair for the
      subtraction
    < nalaginrut> I think the problem is clock is too large for the difference
      between utime and utime(sleep 1)
    < nalaginrut> oops, is too small
    < nalaginrut> sorry, I confused,
    < nalaginrut> the problem is the difference of clock is too large for
      2*internal-time-units-per-second
    < nalaginrut> and actually, internal-time-units-per-second is
      SCM_TIME_UNITS_PER_SECOND
    < nalaginrut> but without your patch, 'times' would return zeros all the
      time, which is never meet the condition: SCM_TIME_UNITS_PER_SECOND/2 <=
      (clock2 - clock1)
    < nalaginrut> well, maybe your point is
      TIME_UNITS_PER_SECOND/ticks_per_second is too small without your patch,
      which causes the scm_to_long cast give a 0 value
    < nalaginrut> s/cast/casting
    < nalaginrut> when ticks_per_second is 100, the factor would be 10, which
      seems to be reasonable
    < nalaginrut> s/scm_to_long/scm_from_long
    < nalaginrut> well, I have to checkout this
    < nalaginrut> OK, let me reconstruct the point: ticks_per_second so too
      large that makes the factor becomes zero
    < nalaginrut> but decrease ticks_per_second to 100 causes the clock become
      too large than  TIME_UNITS_PER_SECOND
    < braunr> 10:59 < nalaginrut> but without your patch, 'times' would return
      zeros all the time, which is never meet the condition:
      SCM_TIME_UNITS_PER_SECOND/2 <= (clock2 - clock1)
    < braunr> until you prove me otherwise, this is plain wrong
    < braunr> times() never returned me 0
    < braunr> so let's see, this gives us a factor of 1000 / 1000000
    < braunr> so the problem is factor being 0
    < braunr> that's why *guile* times returns 0
    < braunr> with my patch it should return 10
    < nalaginrut> braunr:  I'm sorry I mean "stime" in Scheme returns zeros
    < nalaginrut> yes, I think the problem is factor 
    < nalaginrut> the factor
    < braunr> now why doesn't my patch fix it all ?
    < braunr> ah yes, rv is still in microseconds
    < braunr> that's what i've been telling youpi recently, my patch is
      incomplete
    < braunr> i'll cook a quick fix, give me a few minutes please
    < nalaginrut> but it fixed something ;-)
    < braunr> well, guile makes a stupid assumption here
    < braunr> so it's not really a fix
    < nalaginrut> braunr:  should I ask some info about  TIME_UNITS_PER_SECOND
      from Guile community?
    < nalaginrut> or it doesn't help
    < braunr> what do you want to ask them ?
    < nalaginrut> since I don't know how this value was chosen
    < nalaginrut> dunno, I'll ask if you need it
    < nalaginrut> I just think maybe you need this info
    < braunr> well
    < braunr> my plan is to align the hurd on what other archs do
    < braunr> i.e. set clk_tck to 100
    < braunr> in which case this won't be a problem any more
    < braunr> now you could warn them about the protability issue
    < braunr> i'm not sure if they would care though
    < nalaginrut> the warning is useful for the future
    < nalaginrut> and it's not hard to make a change I think, for a constant,
      but it depends on the maintainers
    < braunr> it's not that simple
    < braunr> time related things can easily overflow in the future
    < nalaginrut> alright
    < braunr> refer to the 2038 end-of-the-world bug
    < nalaginrut> so how can I describe the warning/suggestion to them? 
    < braunr> i'm not sure
    < braunr> tell them the TIME_UNITS_PER_SECOND isn't appropriate for larger
      values of clk_tck
    < braunr> dammit, microseconds are hardcoded everywhere in
      sysdeps/mach/hurd ... >(
    < braunr> nalaginrut: my new patch seems to fix the problem
    < braunr> nalaginrut: i've built debian packages with which you can
      directly test
    < braunr> nalaginrut: deb http://ftp.sceen.net/debian-hurd-i386
      experimental/
    < braunr> Totals for this test run:
    < braunr> passes:                 38605
    < braunr> failures:               0
    < braunr> unexpected passes:      0
    < braunr> expected failures:      7
    < braunr> unresolved test cases:  578
    < braunr> untested test cases:    1
    < braunr> unsupported test cases: 10
    < braunr> errors:                 0
    < braunr> PASS: check-guile
    < braunr> =============
    < braunr> 1 test passed
    < braunr> =============
    < braunr> :)
    < braunr> youpi: the branch i added to glibc contains a working patch for
      clock_t in centiseconds
    < youpi> k


### IRC, freenode, #hurd, 2013-08-28

    <nalaginrut> braunr:  well, looks great! I'll try it soon~
    <nalaginrut> braunr:  BTW, where is the patch/
    <mark_weaver> braunr: what was needed to get guile working on the hurd?
    <mark_weaver> well, if the fix wasn't to guile, I don't need the details.
    <braunr> 04:53 < nalaginrut> braunr:  BTW, where is the patch/
    <braunr> there is hardly anyone here at 5am
    <braunr> nalaginrut:
      http://git.savannah.gnu.org/cgit/hurd/glibc.git/log/?h=rbraun/clock_t_centiseconds
    <nalaginrut> braunr:  thanks for that, but why not use a constant for 100?
    <braunr> nalaginrut: i don't know where to define it
    <braunr> it's glibc, you don't define new stuff mindlessly
    <youpi> braunr: about your centiseconds patch, did you run the libc
      testsuite with it?
    <mark_weaver> it does seem a shame to reduce the resolution of the timers
      from microseconds to centiseconds.  I wonder if that could be avoided.
    <youpi> by fixing all applications which assume centiseconds
    <mark_weaver> *nod*  well, if there's such a problem in Guile, I'd be glad
      to fix that.
    <braunr> youpi: no
    <mark_weaver> I see that there's a macro CLOCKS_PER_SEC that programs
      should consult.
    <youpi> braunr: ok, I'll do then
    <braunr> mark_weaver: why is it a shame ?
    <braunr> it's not clock or timer resolution
    <youpi> it's clock_t resolution
    <braunr> it's an obsolete api to measure average cpu usage
    <braunr> having such a big value on the other hand reduces the cpu usage
      durations
    <mark_weaver> braunr: good point :)  I confess to being mostly ignorant of
      these APIs.
    <mark_weaver> Though Guile should still consult CLOCKS_PER_SEC instead of
      assuming centiseconds.  If it's making an improper assumption, I'd like
      to know so I can fix it.
    <braunr> the improper assumption is that there are less than 1000 clock
      ticks per second
    <mark_weaver> do you know off-hand of some code in Guile that is making
      improper assumptions?
    <braunr> yes
    <braunr> let me find it
    <mark_weaver> thanks
    <braunr>   factor = scm_quotient (scm_from_long (TIME_UNITS_PER_SECOND),
    <braunr>                          scm_from_long (ticks_per_second));
    <braunr> it seems guile attempts to normalize all times values to
      TIME_UNITS_PER_SECOND
    <braunr> while i think it would be better off using ticks_per_second (clock
      ticks as provided by sysconf())
    <braunr> attempting to normalize here causes factor to become 0 if
      TIME_UNITS_PER_SECOND < ticks_per_second
    <mark_weaver> ah, I see.
    <mark_weaver> I'll take care of it.  thanks for the pointer!
    <youpi> braunr: I've commited the centisecond patch to debian's glibc


### IRC, freenode, #hurd, 2013-08-29

    <nalaginrut> braunr:  Guile2 works smoothly now, let me try something cool
      with it
    <braunr> nalaginrut: nice


### IRC, OFTC, #debian-hurd, 2013-09-29

    <pinotree> youpi: is the latest glibc carrying the changes related to
      timing? what about gb guile-2.0 with it?
    <youpi> it does
    <youpi> so that was the only issue with guile?
    <youpi> well at least we'll see
    <pinotree> iirc yes
    <pinotree> according to nalaginrut and the latest build log, it'd seem so
    <youpi> started
    <youpi> yay, guile-2.0 :)
    <pinotree> yay