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[[!meta copyright="Copyright © 2011 Free Software Foundation, Inc."]]
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[[!meta title="clock_gettime"]]
[[!tag open_issue_glibc open_issue_gnumach]]
Missing `clock_gettime(CLOCK_MONOTONIC)` (e.g. for iceweasel)
It could be a mere matter of extending the mappable clock: add it to
`mapped_time_value_t` in gnumach, handle it in `gnumach/kern/mach_clock.c`, and
make `clock_gettime` use it.
BTW, also make `gettimeofday()` use it, since it's way more efficient and some
applications assume that it is.
What about adding a nanosecond-precision clock, too? --[[tschwinge]]
IRC, freenode, #hurd, 2011-08-26:
< pinotree> youpi: thing is: apparently i found a simple way to have a
monotonic clock as mmap-able device inside gnumach
< pinotree> currently, in kern/mach_clock.c there's a variable 'time',
which gets increased on clock interrupt, and optionally modified by
host_set_time
< pinotree> ()
< pinotree> if i add a new variable next to it, only increasing it on
interrupt but not modifying it at all otherwise, would that give me a
monotonic clock?
< pinotree> at least on sme basic tests i did, it seems it could work that
way
< youpi> yes, it should work
< braunr> sure
< youpi> and that's the way I was considering implementing it
IRC, freenode, #hurd, 2011-09-06:
<pinotree> yeah, i had a draft of improved idea for also handling
nanoseconds
<tschwinge> pinotree: Ah, nice, I thought about nanoseconds as well.
<tschwinge> pinotree, youpi: This memory page is all-zero by default,
right?
<tschwinge> Can't we then say that its last int is a version code, and if
it is 0 (as it is now), we only have the normal mapped time field, if it
is 1, we also have the monotonic cliock and ns precision on address 8 and
16 (or whatever)?
<tschwinge> In case that isn't your plan anyway.
<youpi> it's all-zero, yes
<tschwinge> Or, we say if a field is != 0 it is valid.
<youpi> making the last int a version code limits the size to one page
<youpi> I was thinking a field != 0 being valid is simpler
<youpi> but it's probably a problem too
<youpi> in that glibc usually caches whether interfaces are supported
<tschwinge> Wrap-around?
<youpi> for some clocks, it may be valid that the value is 0
<youpi> wrap-around is another issue too
<tschwinge> Well, then we can do the version-field thing, but put it right
after the current time field (address 8, I think)?
<youpi> yes
<youpi> it's a bit ugly, but it's hidden behind the structure
<tschwinge> It's not too bad, I think.
<youpi> yes
<tschwinge> And it will forever be a witness of the evolving of this
map_time interface. :-)
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