Re: [PATCH, v2] anon_vmas: Convert the rwsem to an rwlock_t

[Tim Chen <tim.c.chen@linux.intel.com>]

On Mon, 2013-09-30 at 12:47 -0700, Tim Chen wrote:
> On Mon, 2013-09-30 at 15:35 -0400, Waiman Long wrote:
> > On 09/30/2013 03:23 PM, Tim Chen wrote:
> > > On Mon, 2013-09-30 at 20:14 +0200, Peter Zijlstra wrote:
> > >> On Mon, Sep 30, 2013 at 10:10:27AM -0700, Tim Chen wrote:
> > >>> Here's the exim workload data:
> > >>>
> > >>> rwsem improvment:
> > >>> Waimain's patch:        +2.0%
> > >>> Alex+Tim's patchset:    +4.8%
> > >>> Waiman+Alex+Tim:        +5.3%
> > >>>
> > >>> convert rwsem to rwlock_t for root anon_vma lock
> > >>> Ingo's patch		+11.7%
> > >>>
> > >> What happens if you stuff Waiman's qrwlock patches on top of that?
> > >> admittedly and oft mentioned in this thread, our current rwlock_t is
> > >> somewhat suboptimal under a number of conditions.
> > > I've tested with Waiman's qrwlock patches on top of Ingo's patches.
> > > It does not affect the throughput for exim and I still get
> > > about +11.7% throughput change (same as with Ingo's patch only).
> > >
> > > Tim
> > >
> > 
> > My qrwlock doesn't enable qrwlock by default. You have to use menuconfig 
> > to explicitly enable it. Have you done that when you build the test 
> > kernel? I am thinking of explicitly enabling it for x86 if the anon-vma 
> > lock is converted back to a rwlock.
> > 
> 
> Yes, I have explicitly enabled it during my testing.
> 
The workload I have is dominated by writer locks, with only very
occasional readers. So it may not benefit from the various tweaks you
have put in qrwlock.

Tim