Re: [RFC PATCH v2 0/4] Eliminate zone->lock contention for will-it-scale/page_fault1 and parallel free

[Daniel Jordan]

On 03/29/2018 09:42 PM, Aaron Lu wrote:
> On Thu, Mar 29, 2018 at 03:19:46PM -0400, Daniel Jordan wrote:
> > On 03/20/2018 04:54 AM, Aaron Lu wrote:
> > > This series is meant to improve zone->lock scalability for order 0 pages.
> > > With will-it-scale/page_fault1 workload, on a 2 sockets Intel Skylake
> > > server with 112 CPUs, CPU spend 80% of its time spinning on zone->lock.
> > > Perf profile shows the most time consuming part under zone->lock is the
> > > cache miss on "struct page", so here I'm trying to avoid those cache
> > > misses.
> >
> > I ran page_fault1 comparing 4.16-rc5 to your recent work, these four patches
> > plus the three others from your github branch zone_lock_rfc_v2. Out of
> > curiosity I also threw in another 4.16-rc5 with the pcp batch size adjusted
> > so high (10922 pages) that we always stay in the pcp lists and out of buddy
> > completely.  I used your patch[*] in this last kernel.
> >
> > This was on a 2-socket, 20-core broadwell server.
> >
> > There were some small regressions a bit outside the noise at low process
> > counts (2-5) but I'm not sure they're repeatable.  Anyway, it does improve
> > the microbenchmark across the board.
>
> Thanks for the result.
>
> The limited improvement is expected since lock contention only shifts,
> not entirely gone. So what is interesting to see is how it performs with
> v4.16-rc5 + my_zone_lock_patchset + your_lru_lock_patchset

Yep, that's 'coming soon.'