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Tue, 07 Apr 2026 07:27:32 -0700 (PDT) MIME-Version: 1.0 References: <20260318011558.1696310-1-zhaoyang.huang@unisoc.com> In-Reply-To: <20260318011558.1696310-1-zhaoyang.huang@unisoc.com> From: Kairui Song Date: Tue, 7 Apr 2026 22:26:55 +0800 X-Gm-Features: AQROBzA7rGwe-g8C1Axq71zPgt00Tvht1COp-g4aqx_S-9pNTZiYj7hTCxrgauQ Message-ID: Subject: Re: [PATCHv3] mm: remove '!root_reclaim' checking in should_abort_scan() To: "zhaoyang.huang" Cc: Andrew Morton , Michal Hocko , "T . J . Mercier" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Zhaoyang Huang , steve.kang@unisoc.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 916DD100013 X-Stat-Signature: 9au3jfd7a1bjuema8xj1osjch6trntd7 X-Rspam-User: X-HE-Tag: 1775572054-535064 X-HE-Meta: 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 sRut7diQ 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Mar 18, 2026 at 9:17=E2=80=AFAM zhaoyang.huang wrote: > > From: Zhaoyang Huang > > Android systems usually use memory.reclaim interface to implement user > space memory management which expects that the requested reclaim target > and actually reclaimed amount memory are not diverging by too much. With > the current MGRLU implementation there is, however, no bail out when the > reclaim target is reached and this could lead to an excessive reclaim > that scales with the reclaim hierarchy size.For example, we can get a > nr_reclaimed=3D394/nr_to_reclaim=3D32 proactive reclaim under a common 1-= N > cgroup hierarchy. > This defect arised from the goal of keeping fairness among memcgs that > is, for try_to_free_mem_cgroup_pages -> shrink_node_memcgs -> > shrink_lruvec -> lru_gen_shrink_lruvec -> try_to_shrink_lruvec, the > !root_reclaim(sc) check was there for reclaim fairness, which was > necessary before commit 'b82b530740b9' ("mm: vmscan: restore > incremental cgroup iteration") because the fairness depended on > attempted proportional reclaim from every memcg under the target > memcg. However after commit 'b82b530740b9' there is no longer a need Hi Zhaoyang, A nitpick here, this is triggering an error with checkpatch.pl: ./scripts/checkpatch.pl 0001-mm-remove-root_reclaim-checking-in-should_abort_scan.patch ERROR: Please use git commit description style 'commit <12+ chars of sha1> ("")' - ie: 'commit b82b530740b9 ("mm: vmscan: restore incremental cgroup iteration")' #23: under the target memcg. However after commit b82b530740b9 there is no total: 1 errors, 0 warnings, 10 lines checked A lot of auto tools recognize that commit message format and print warning, Better to follow the rule unless necessary. > to visit every memcg to ensure fairness. Let's have try_to_shrink_lruvec > bail out when the nr_reclaimed achieved. > > Suggested-by: T.J.Mercier <tjmercier@google.com> > Reviewed-by: T.J.Mercier <tjmercier@google.com> > Signed-off-by: Zhaoyang Huang <zhaoyang.huang@unisoc.com> > --- > Patchv2,v3: update commit message > --- > --- > mm/vmscan.c | 4 ---- > 1 file changed, 4 deletions(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 0fc9373e8251..10f1e7d716ca 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -4839,10 +4839,6 @@ static bool should_abort_scan(struct lruvec *lruve= c, struct scan_control *sc) > int i; > enum zone_watermarks mark; > > - /* don't abort memcg reclaim to ensure fairness */ > - if (!root_reclaim(sc)) > - return false; > - Makes sense to me combined with b82b530740b9. I've been testing on top of your commit and it seems all good: Reviewed-by: Kairui Song <kasong@tencent.com>