path: root/open_issues/tty_activitiy_vs_disk_io.mdwn
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author <diana@web>2015-02-16 20:08:03 +0100
committerGNU Hurd web pages engine <>2015-02-16 20:08:03 +0100
commit95878586ec7611791f4001a4ee17abf943fae3c1 (patch)
tree847cf658ab3c3208a296202194b16a6550b243cf /open_issues/tty_activitiy_vs_disk_io.mdwn
parent8063426bf7848411b0ef3626d57be8cb4826715e (diff)
rename open_issues.mdwn to service_solahart_jakarta_selatan__082122541663.mdwn
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-[[!meta copyright="Copyright © 2011 Free Software Foundation, Inc."]]
-[[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable
-id="license" text="Permission is granted to copy, distribute and/or modify this
-document under the terms of the GNU Free Documentation License, Version 1.2 or
-any later version published by the Free Software Foundation; with no Invariant
-Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license
-is included in the section entitled [[GNU Free Documentation
-[[!tag open_issue_hurd]]
-IRC, freenode, #hurd, 2011-07-25
- < youpi> Mmm, typing something on the mach console triggers a write on the
- disk
- < youpi> because the /dev/console node gets updated
- < youpi> I don't really see why
- < youpi> (yes, just typing at the bash prompt, not even running something)
- < youpi> typing during the sleep command (i.e. mere tty echo) doesn't
- trigger it, however
- < youpi> running bash's echo does trigger it
- < braunr> during sleep, the glibc stream functions handle I/O, while with
- bash, its readline takes care of it, right ?
- < youpi> /bin/echo too
- < youpi> during sleep it's the tty process which handles I/O
- < braunr> the write may be due to a write time update on the inode
- < braunr> modification* time
- < youpi> probably yes, but how so?
- < youpi> ext2fs is only supposed to pass the thing to the console
- translator
- < braunr> not sure
- < youpi> actually, ext2fs even isn't supposed to come into play when it's
- about typing at the bash prompt
- < youpi> once it's opened, isn't the port for /dev/console supposed to be
- directly to the translator there?
- < braunr> i think so
- < youpi> (s/tty/term/ in what I said)
- < braunr> well, it's certain
- < youpi> so I don't see how ext2fs can be triggered to write an atime or
- mtime
- < braunr> what does rpctrace say ?
- < youpi> io_read_request and io_write_request
- < youpi> braunr: it doesn't happen at the login prompt
- < youpi> interestingly, atime is always 3-4 secs earlier than ctime & mtime
- < youpi> doesn't happen with dash
- < braunr> we should implement relatime and experiment with it
- < braunr> it shouldn't be hard
- < youpi> well, there's noatime already
- < youpi> but my point is that this update shouldn't happen
- < youpi> and I believe it's the source of the i_file_acl e2fsck warning
- < braunr> i wasn't saying that concerning this problem, it was just a
- separate idea (noatime is more problematic than relatime)
- < braunr> and i agree, it shouldn't happen :)
- < youpi> ok, it's set_node_times which gets called
-IRC, freenode, #hurd, 2011-07-27
- < antrik> BTW, I'm not sure it's still relevant; but the reason accessing
- translators such as the console modifies the underlying node is that most
- stat information is generally passed through
- < antrik> (in some cases it might be unintentional though, simply using the
- default implementation from trivfs carelessly...)
- < youpi> I know
- < youpi> I've seen that in the code
- < antrik> OK
- < youpi> it is still relevant: I still find it useless to write it on the
- disk
- < youpi> though w uses it to show idle time over reboot
- < braunr> is it useful to keep the information across reboots ?
- < youpi> for some value of "useful" for w
- < braunr> i wonder what would break if this was entierly kept in memory
- < youpi> nothing, probably
- < youpi> note that it doesn't overload ext2fs so much, it just adds a write
- every ~5s
- < youpi> (at worse, i.e. when keeping showing text, for instance)
- < braunr> indeed, the behaviour seems the same on linux
- < antrik> ah... that explains why the disk doesn't spin down while IRC is
- active... always wondered about that :-)
- < youpi> that's not very power-saving, yes
- < youpi> well, we might want to put /dev on ram someday