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Tue, 07 Apr 2026 18:43:01 -0700 (PDT) MIME-Version: 1.0 References: <20260318011558.1696310-1-zhaoyang.huang@unisoc.com> In-Reply-To: From: Zhaoyang Huang Date: Wed, 8 Apr 2026 09:42:48 +0800 X-Gm-Features: AQROBzBUHg_Em7QzqowrnsecjX6CiRCG-Ek9DSeqq2r1soPC22myVEb7HMx0EOg Message-ID: Subject: Re: [PATCHv3] mm: remove '!root_reclaim' checking in should_abort_scan() To: Kairui Song Cc: "zhaoyang.huang" , Andrew Morton , Michal Hocko , "T . J . Mercier" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, steve.kang@unisoc.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 9CE2010000A X-Stat-Signature: epo9wi4htuog8xdru5it8isazprgkozt X-Rspam-User: X-HE-Tag: 1775612583-779577 X-HE-Meta: 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 nmjqtioQ 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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 Tue, Apr 7, 2026 at 10:27=E2=80=AFPM Kairui Song wrot= e: > > 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. Wit= h > > the current MGRLU implementation there is, however, no bail out when th= e > > 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 Hi Kairui, Thanks for heads up. It is weird that I got the result as Yes/Err/Err by latest checkpatch.pl for the following three styles as <after commit 'b82b530740b9' there / after commit b82b530740b9 there / after 'commit b82b530740b9' there>. Is it possible that the result depends on the local environment? > 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_lruve= c > > 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 *lru= vec, 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>