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author | Thomas Schwinge <tschwinge@gnu.org> | 2013-04-07 18:18:44 +0200 |
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committer | Thomas Schwinge <tschwinge@gnu.org> | 2013-04-07 18:18:44 +0200 |
commit | 6c7d45e4631784d0e077e806521a736da6b0266e (patch) | |
tree | f9d3e9ed304e8cdbf72fc77c135781eb49990f6a /open_issues/pfinet_timers.mdwn | |
parent | f8ed211a4da23edf469089254b3dace9479bf11f (diff) | |
download | web-6c7d45e4631784d0e077e806521a736da6b0266e.tar.gz web-6c7d45e4631784d0e077e806521a736da6b0266e.tar.bz2 web-6c7d45e4631784d0e077e806521a736da6b0266e.zip |
IRC.
Diffstat (limited to 'open_issues/pfinet_timers.mdwn')
-rw-r--r-- | open_issues/pfinet_timers.mdwn | 102 |
1 files changed, 102 insertions, 0 deletions
diff --git a/open_issues/pfinet_timers.mdwn b/open_issues/pfinet_timers.mdwn index 387ad4fe..5db192e3 100644 --- a/open_issues/pfinet_timers.mdwn +++ b/open_issues/pfinet_timers.mdwn @@ -15,3 +15,105 @@ License|/fdl]]."]]"""]] <braunr> now that there is a pthread_hurd_cond_timedwait_np function available, we could replace the ulgy timers in pfinet + + +# IRC, freenode, #hurd, 2013-04-02 + + <braunr> youpi: also, i think i know why fakeroot is slow on the hurd + <braunr> well, pfinet actually + <youpi> tcp flow control? + <braunr> i think it's because of our timer resolution + <youpi> ah + <braunr> and i think i spotted a small mistake in the timer emulation code + btw + <braunr> it's so obvious i even doubt it's actually true :) + <braunr> see timer_emul.c:timer_function + <braunr> the code checks for timers->expires < jiffies + <braunr> shouldn't it be "<=" + <braunr> ? + <youpi> well it'd be equivalent + <youpi> if ==, then wait becomes 0 in the else + <braunr> see the second scheck + <braunr> the one performed right before running the callback + <youpi> ah, the while? + <braunr> yes + <youpi> I'd say <= could do it yes + <braunr> ok + <braunr> i have hurd packages ready to be tested + <youpi> although I'm unsure it'd make a difference + <youpi> do you notice some? + <braunr> just waiting for my current glibc to finish building + <braunr> and i'll test right after + <braunr> i think it would actually + <youpi> in which case? + <braunr> the timer resolution is 10ms + <braunr> it's huge + <braunr> well, i hope it fixes fakeroot slowness :) + <youpi> so timers below that would trigger immediately? + <braunr> or equal + <braunr> taht's the problem + <braunr> for 10ms, timers that have expired must wait for the next tick to + fire + <youpi> I include "equal" in below + <youpi> actually :) + <braunr> then yes :) + <braunr> soryy i never know when equal is implicit + <youpi> because they boil down to expires = jiffies + <youpi> in french it's implicit + <youpi> but anyway here equal is not really important + <braunr> right + <braunr> why ? + <youpi> it's the fact that 1ms would be rounded up to 10ms, not down to 0ms + <braunr> well, doing that seems reasonable + <youpi> or rather, rounded down to 0ms, but waited for 10ms because of the + < + <braunr> we do want timers not to fire before the time event + <youpi> I'm however wondering which part of the code would have timer below + 10ms + <braunr> well, a select with low timeout from a client perhaps ? + <youpi> but then we have to round up + <youpi> as you say we don't want to fire before some time + <braunr> well yes + <braunr> that's fine + <youpi> all that being said, linux has been having 10ms clock for a long + time + <braunr> but when the timer fires, i.e. when expires == jiffie, we do want + it to fire + <youpi> highres timers are only relativeley recent + <braunr> not at jiffie + 1 + <youpi> braunr: ah, right, so we don't wait for 20ms instead of 10ms + <braunr> yes + <youpi> ok, so it's not a miracle fix, but could bring 2times fix + <braunr> well, pfinet eats 40% of my processor when this problem occurs + <braunr> which i'm seeing right now + <youpi> yes, I've seen that too + <braunr> so it may be a visible win + <braunr> build finished :) let's see + <youpi> Mmm, thinking again + <youpi> indeed + <youpi> when expires become jiffies + <youpi> we mach_msg (0) + <youpi> but don't do anything + <youpi> and then restart + <youpi> so just eaten cpu for nothing + <braunr> is there a small package that builds fast and uses fakeroot a lot + ? + <youpi> something like a package which has a lot of data to install at make + install + <braunr> or i can rebuild glibc with -nc + <youpi> ok, I've checked in linux + <pinotree> libarchive's testsuite used to intermittently failing under + fakeroot + <youpi> it's definitely <= which is meant + <braunr> it looks better + <braunr> but still not 100% cpu + <youpi> at any rate, as long as it doesn't seem to break anything, please + push the fix + <youpi> it definitely makes sense + <youpi> (and I don't see why it could break anything) + <braunr> ok + <braunr> i'll look into this timer problem a bit more, there may be other + code involved + <braunr> yes, schedule_timeout could need a review + <braunr> actually, fakeroot rm -rf * is a good test + <braunr> and it's still damn slow |