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Diffstat (limited to 'open_issues/tty_activitiy_vs_disk_io.mdwn')
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diff --git a/open_issues/tty_activitiy_vs_disk_io.mdwn b/open_issues/tty_activitiy_vs_disk_io.mdwn new file mode 100644 index 00000000..26382d56 --- /dev/null +++ b/open_issues/tty_activitiy_vs_disk_io.mdwn @@ -0,0 +1,81 @@ +[[!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 +License|/fdl]]."]]"""]] + +[[!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 |