Messages in this thread | | | Date | Mon, 09 Sep 2013 10:34:45 +0800 | From | Daniel J Blueman <> | Subject | Re: [PATCH 2/2] thp: support split page table lock |
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On Saturday, 7 September 2013 02:10:02 UTC+8, Naoya Horiguchi wrote: > Hi Alex, > > On Fri, Sep 06, 2013 at 11:04:23AM -0500, Alex Thorlton wrote: > > On Thu, Sep 05, 2013 at 05:27:46PM -0400, Naoya Horiguchi wrote: > > > Thp related code also uses per process mm->page_table_lock now. > > > So making it fine-grained can provide better performance. > > > > > > This patch makes thp support split page table lock by using page->ptl > > > of the pages storing "pmd_trans_huge" pmds. > > > > > > Some functions like pmd_trans_huge_lock() and page_check_address_pmd() > > > are expected by their caller to pass back the pointer of ptl, so this > > > patch adds to those functions new arguments for that. Rather than that, > > > this patch gives only straightforward replacement. > > > > > > ChangeLog v3: > > > - fixed argument of huge_pmd_lockptr() in copy_huge_pmd() > > > - added missing declaration of ptl in do_huge_pmd_anonymous_page() > > > > I've applied these and tested them using the same tests program that I > > used when I was working on the same issue, and I'm running into some > > bugs. Here's a stack trace: > > Thank you for helping testing. This bug is new to me.
With 3.11, this patch series and CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS, I consistently hit the same failure when exiting one of my stress-testers [1] when using eg 24 cores.
Doesn't happen with 8 cores, so likely needs enough virtual memory to use multiple split locks. Otherwise, this is very promising work!
[1] http://quora.org/2013/fft3d.c -- Daniel J Blueman Principal Software Engineer, Numascale
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