Messages in this thread | | | Date | Sun, 11 Apr 2004 17:09:57 +0100 (BST) | From | Hugh Dickins <> | Subject | Re: [PATCH] anobjrmap 9 priority mjb tree |
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On Fri, 9 Apr 2004, Martin J. Bligh wrote: > >> This slows down kernel compile a little, but worse, it slows down SDET > >> by about 25% (on the 16x). I think you did something horrible to sem > >> contention ... presumably i_shared_sem, which SDET was fighting with > >> as it was anyway ;-( > >> > >> Diffprofile shows: > >> > >> 122626 15.7% total > >> 44129 790.0% __down > >> 20988 4.1% default_idle > > I applied Andrew's high sophisticated proprietary semtrace technology.
Thanks a lot, Martin, this seems pretty important.
So, i_shared_sem, as you supposed.
Do you still have the two profiles input to diffprofile? I wonder if they'd have clues to help us understand it better.
Any chance of you doing the same comparison between 2.6.5-aa5 2.6.5-aa5 minus prio-tree? (Well, needn't be -aa5, whatever comes to hand. Looks like "patch -p1 -R < prio-tree" mostly works, just some rejects in mm/mmap.c itself, let me know if I can help out on that.)
If -aa is okay, I hope so, then it's surely some stupidity from me.
We're not at all surprised that vma linking and unlinking should take rather longer; but the rise in __down, __wake_up, finish_task_switch is horrifying. Or is that how it usually looks, when a semaphore is well contended - thundering herd?
Hugh
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