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Tue, 28 Mar 2023 08:18:22 -0700 (PDT) MIME-Version: 1.0 References: <20230328061638.203420-1-yosryahmed@google.com> <20230328061638.203420-8-yosryahmed@google.com> In-Reply-To: <20230328061638.203420-8-yosryahmed@google.com> From: Shakeel Butt Date: Tue, 28 Mar 2023 08:18:11 -0700 Message-ID: Subject: Re: [PATCH v1 7/9] workingset: memcg: sleep when flushing stats in workingset_refault() To: Yosry Ahmed Cc: Tejun Heo , Josef Bacik , Jens Axboe , Zefan Li , Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , Andrew Morton , =?UTF-8?Q?Michal_Koutn=C3=BD?= , Vasily Averin , cgroups@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, bpf@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Queue-Id: 2ABA080009 X-Rspamd-Server: rspam01 X-Stat-Signature: jte7q9mb5jpj6myck88jrjyeja95saup X-HE-Tag: 1680016702-271329 X-HE-Meta: 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 XKQTJRFr c0JCQ6m/v1SjoS4NTptSIMc/gpmV6cj1SMMA/KZMWa2FAisRC4ku2fFmScSMeT3MTtl0iZ3mBW6HNq5dX+vHGu+cdnlchs8rEwnahp2BLMvGB7/aZSque2B5nqNuAooyUjZHGQBchAx0XKwhCxgg/J4kDyzvGN1o9ELArwdtDaESA1dNFsCg+TSBit1S/2Z0FJX7qQ/IG6l4z1pX2d6IhlVs5Ntt0kgRhZPhJ08E37utT6ZHrELWv7Z6o1s1KPunDeV0ZfB3Nf++Gkw52YzI6+MjGZC72Ix+jfgJ5KKeebCE8/rDrPhxICUOnfg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Mar 27, 2023 at 11:16=E2=80=AFPM Yosry Ahmed wrote: > > In workingset_refault(), we call mem_cgroup_flush_stats_ratelimited() > to flush stats within an RCU read section and with sleeping disallowed. > Move the call to mem_cgroup_flush_stats_ratelimited() above the RCU read > section and allow sleeping to avoid unnecessarily performing a lot of > work without sleeping. > > Since workingset_refault() is the only caller of > mem_cgroup_flush_stats_ratelimited(), just make it call the non-atomic > mem_cgroup_flush_stats(). > > Signed-off-by: Yosry Ahmed A nit below: Acked-by: Shakeel Butt > --- > mm/memcontrol.c | 12 ++++++------ > mm/workingset.c | 4 ++-- > 2 files changed, 8 insertions(+), 8 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 57e8cbf701f3..0c0e74188e90 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -674,12 +674,6 @@ void mem_cgroup_flush_stats_atomic(void) > __mem_cgroup_flush_stats_atomic(); > } > > -void mem_cgroup_flush_stats_ratelimited(void) > -{ > - if (time_after64(jiffies_64, READ_ONCE(flush_next_time))) > - mem_cgroup_flush_stats_atomic(); > -} > - > /* non-atomic functions, only safe from sleepable contexts */ > static void __mem_cgroup_flush_stats(void) > { > @@ -695,6 +689,12 @@ void mem_cgroup_flush_stats(void) > __mem_cgroup_flush_stats(); > } > > +void mem_cgroup_flush_stats_ratelimited(void) > +{ > + if (time_after64(jiffies_64, READ_ONCE(flush_next_time))) > + mem_cgroup_flush_stats(); > +} > + > static void flush_memcg_stats_dwork(struct work_struct *w) > { > __mem_cgroup_flush_stats(); > diff --git a/mm/workingset.c b/mm/workingset.c > index af862c6738c3..7d7ecc46521c 100644 > --- a/mm/workingset.c > +++ b/mm/workingset.c > @@ -406,6 +406,8 @@ void workingset_refault(struct folio *folio, void *sh= adow) > unpack_shadow(shadow, &memcgid, &pgdat, &eviction, &workingset); > eviction <<=3D bucket_order; > > + /* Flush stats (and potentially sleep) before holding RCU read lo= ck */ I think the only reason we use rcu lock is due to mem_cgroup_from_id(). Maybe we should add mem_cgroup_tryget_from_id(). The other caller of mem_cgroup_from_id() in vmscan is already doing the same and could use mem_cgroup_tryget_from_id(). Though this can be done separately to this series (if we decide to do it at all).