Messages in this thread | | | From | Steven Cole <> | Subject | Re: 1352 NUL bytes at the end of a page? (was Re: Assertion `s && s->tree' failed: The saga continues.) | Date | Sun, 16 May 2004 09:28:21 -0600 |
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On Saturday 15 May 2004 11:22 pm, Andrea Arcangeli wrote: > On Sat, May 15, 2004 at 09:52:50PM -0700, Linus Torvalds wrote: > > > > > > On Sat, 15 May 2004, Steven Cole wrote: > > > > > > OK, will do. I ran the bk exerciser script for over an hour with 2.6.6-current > > > and no CONFIG_PREEMPT and no errors. The script only reported one > > > iteration finished, while I got it to do 36 iterations over several hours earlier > > > today (with a 2.6.3-4mdk vendor kernel) > > > > Hmm.. Th ecurrent BK tree contains much of the anonvma stuff, so this > > might actually be a serious VM performance regression. That could > > effectively be hiding whatever problem you saw. > > > > Andrea: have you tested under low memory and high fs load? Steven has 384M > > or RAM, which _will_ cause a lot of VM activity when doing a full kernel > > BK clone + undo + pull, which is what his test script ends up doing... > > An easy way to verify for Steven is to give a quick spin to 2.6.5-aa5 > and see if it's slow too, that will rule out the anon-vma changes > (for completeness: there's a minor race in 2.6.5-aa5 fixed in my current > internal tree, I posted the fix to l-k separately, but you can ignore > the fix for a simple test, it takes weeks to trigger anyways and you > need threads to trigger it and I've never seen threaded version control > systems so I doubt BK is threaded).
I'm getting the linux-2.6.5.tar.bz2 file (already got 2.6.5-aa2) via ppp, while running the bk test script on 2.6.6-current and no PREEMPT. That takes a while on 56k dialup. I'll leave all that running while I go hiking.
> > In general a "slowdown" cannot be related to anon-vma (unless it's a > minor merging error), that's a black and white thing, it doesn't touch > the vm heuristics and it will only speed the fast paths up plus it will > save some tons of ram in the big systems. Pratically no change should be > measurable on a small system (unless it uses an heavy amount of cows, in > which case it will improve things, it should never hurt). As for being > tested, it is very well tested on the small desktops too. Probably the > only thing to double check is that there was no minor merging error that > could have caused this.
Andrea, I did see a significant slowdown with Andy's test script (with DMA on) on my timed test of 2.6.6-current vs 2.6.3.
> > > It would be good to test going back to the kernel that saw the "immediate > > problem", and try that version without CONFIG_PREEMPT. > > Agreed. > > Thanks. > >
Yep, later this evening, I hope.
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