lkml.org 
[lkml]   [2009]   [Sep]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: aim7 scalability issue on 4 socket machine
From
Date
On Thu, 2009-09-17 at 11:35 +0100, Hugh Dickins wrote:
> On Thu, 17 Sep 2009, Peter Zijlstra wrote:
> > On Thu, 2009-09-17 at 17:31 +0800, Zhang, Yanmin wrote:
> > > Aim7 result is bad on my new Nehalem machines (4*8*2 logical cpu). Perf counter
> > > shows spinlock consumes 70% cpu time on the machine. Lock_stat shows
> > > anon_vma->lock causes most of the spinlock contention. Function tracer shows
> > > below call chain creates the spinlock.
> > >
> > > do_brk => vma_merge =>vma_adjust
> > >
> > > Aim7 consists of lots of subtests. One test is to fork lots of processes and
> > > every process calls sbrk for 1000 times to grow/shrink the heap. All the vma of
> > > the heap of all sub-processes point to the same anon_vma and use the same
> > > anon_vma->lock. When sbrk is called, kernel calls do_brk => vma_merge =>vma_adjust
> > > and lock anon_vma->lock to create spinlock contentions.
> > >
> > > There is a comment section in front of spin_lock(&anon_vma->lock. It says
> > > anon_vma lock can be optimized when just changing vma->vm_end. As a matter
> > > of fact, anon_vma->lock is used to protect anon_vma->list when an entry is
> > > deleted/inserted or the list is accessed. There is no such deletion/insertion
> > > if only vma->end is changed in function vma_adjust.
> > >
> > > Below patch fixes it.
> > >
> > > Test results with kernel 2.6.31-rc8. The improvement on the machine is about 150%.
> >
> > Did you see Lee's patch?:
> >
> > http://lkml.org/lkml/2009/9/9/290
> >
> > Added Lee and Hugh to CC, retained the below patch for them.
>
> Thanks a lot for the CC, Peter.
> See my reply to that mail for the slightly corrected version.
>
> Yes, Yanmin and Lee appear to be fixing exactly the same issue.
> I haven't thought through Yanmin's version for correctness, but
> it lacks the vm_start check I added to Lee's, and I do prefer
> Lee's style - hey, nothing personal!
>
> So, Yanmin, please retest with http://lkml.org/lkml/2009/9/13/25
> and let us know if that works as well for you - thanks.
I tested Lee's patch and it does fix the issue.

Yanmin




\
 
 \ /
  Last update: 2009-09-18 04:03    [W:0.212 / U:0.200 seconds]
©2003-2014 Jasper Spaans. Advertise on this site