[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <Y9PEoOAxE1hlnH5o@dhcp22.suse.cz>
Date: Fri, 27 Jan 2023 13:33:36 +0100
From: Michal Hocko <mhocko@...e.com>
To: Hyeonggon Yoo <42.hyeyoo@...il.com>
Cc: Vlastimil Babka <vbabka@...e.cz>,
Andrew Morton <akpm@...ux-foundation.org>,
Christoph Lameter <cl@...ux.com>,
Pekka Enberg <penberg@...nel.org>,
David Rientjes <rientjes@...gle.com>,
Joonsoo Kim <iamjoonsoo.kim@....com>,
Roman Gushchin <roman.gushchin@...ux.dev>,
Ingo Molnar <mingo@...hat.com>,
Johannes Weiner <hannes@...xchg.org>,
Shakeel Butt <shakeelb@...gle.com>,
Muchun Song <muchun.song@...ux.dev>,
Matthew Wilcox <willy@...radead.org>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org,
Peter Zijlstra <peterz@...radead.org>,
Juri Lelli <juri.lelli@...hat.com>,
Vincent Guittot <vincent.guittot@...aro.org>,
Dietmar Eggemann <dietmar.eggemann@....com>,
Steven Rostedt <rostedt@...dmis.org>,
Ben Segall <bsegall@...gle.com>,
Mel Gorman <mgorman@...hsingularity.net>,
Daniel Bristot de Oliveira <bristot@...hat.com>,
Valentin Schneider <vschneid@...hat.com>,
Dennis Zhou <dennis@...nel.org>, Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH mm-unstable] lib/Kconfig.debug: do not enable
DEBUG_PREEMPT by default
On Fri 27-01-23 20:43:20, Hyeonggon Yoo wrote:
> On Wed, Jan 25, 2023 at 10:51:05AM +0100, Michal Hocko wrote:
> > On Thu 26-01-23 00:41:15, Hyeonggon Yoo wrote:
> > [...]
> > > > Do you happen to have any perf data collected during those runs? I
> > > > would be interested in the memcg side of things. Maybe we can do
> > > > something better there.
> > >
> > > Yes, below is performance data I've collected.
> > >
> > > 6.1.8-debug-preempt-dirty
> > > =========================
> > > Overhead Command Shared Object Symbol
> > > + 9.14% hackbench [kernel.vmlinux] [k] check_preemption_disabled
> >
> > Thanks! Could you just add callers that are showing in the profile for
> > this call please?
>
> - 14.56% 9.14% hackbench [kernel.vmlinux] [k] check_preemption_disabled
> - 6.37% check_preemption_disabled
> + 3.48% mod_objcg_state
> + 1.10% obj_cgroup_charge
> 1.02% refill_obj_stock
> 0.67% memcg_slab_post_alloc_hook
> 0.58% mod_objcg_state
>
> According to perf, many memcg functions call this function
> and that's because __this_cpu_xxxx checks if preemption is disabled.
OK, I see. Thanks! I was thinking whether we can optimize for that bu
IIUC __this_cpu* is already an optimized form. mod_objcg_state is
already called with local_lock so raw_cpu* could be used in that path
but I guess this is not really worth just to optimize for a debug
compile option to benefit.
--
Michal Hocko
SUSE Labs
Powered by blists - more mailing lists