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[73.93.239.127]) by smtp.gmail.com with ESMTPSA id y12sm99220pjc.56.2021.02.16.16.13.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 16 Feb 2021 16:13:56 -0800 (PST) From: Yang Shi To: guro@fb.com, ktkhai@virtuozzo.com, vbabka@suse.cz, shakeelb@google.com, david@fromorbit.com, hannes@cmpxchg.org, mhocko@suse.com, akpm@linux-foundation.org Cc: shy828301@gmail.com, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [v8 PATCH 13/13] mm: vmscan: shrink deferred objects proportional to priority Date: Tue, 16 Feb 2021 16:13:22 -0800 Message-Id: <20210217001322.2226796-14-shy828301@gmail.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20210217001322.2226796-1-shy828301@gmail.com> References: <20210217001322.2226796-1-shy828301@gmail.com> MIME-Version: 1.0 X-Stat-Signature: wrdi8qpxbfizkdemyzc1cahhn84hu9yt X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 80387407F8ED Received-SPF: none (gmail.com>: No applicable sender policy available) receiver=imf02; identity=mailfrom; envelope-from=""; helo=mail-pf1-f178.google.com; client-ip=209.85.210.178 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1613520831-369691 Content-Transfer-Encoding: quoted-printable 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: The number of deferred objects might get windup to an absurd number, and = it results in clamp of slab objects. It is undesirable for sustaining worki= ngset. So shrink deferred objects proportional to priority and cap nr_deferred t= o twice of cache items. The idea is borrowed from Dave Chinner's patch: https://lore.kernel.org/linux-xfs/20191031234618.15403-13-david@fromorbit= .com/ Tested with kernel build and vfs metadata heavy workload in our productio= n environment, no regression is spotted so far. Signed-off-by: Yang Shi --- mm/vmscan.c | 46 +++++++++++----------------------------------- 1 file changed, 11 insertions(+), 35 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 4247a3568585..b3bdc3ba8edc 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -661,7 +661,6 @@ static unsigned long do_shrink_slab(struct shrink_con= trol *shrinkctl, */ nr =3D xchg_nr_deferred(shrinker, shrinkctl); =20 - total_scan =3D nr; if (shrinker->seeks) { delta =3D freeable >> priority; delta *=3D 4; @@ -675,37 +674,9 @@ static unsigned long do_shrink_slab(struct shrink_co= ntrol *shrinkctl, delta =3D freeable / 2; } =20 + total_scan =3D nr >> priority; total_scan +=3D delta; - if (total_scan < 0) { - pr_err("shrink_slab: %pS negative objects to delete nr=3D%ld\n", - shrinker->scan_objects, total_scan); - total_scan =3D freeable; - next_deferred =3D nr; - } else - next_deferred =3D total_scan; - - /* - * We need to avoid excessive windup on filesystem shrinkers - * due to large numbers of GFP_NOFS allocations causing the - * shrinkers to return -1 all the time. This results in a large - * nr being built up so when a shrink that can do some work - * comes along it empties the entire cache due to nr >>> - * freeable. This is bad for sustaining a working set in - * memory. - * - * Hence only allow the shrinker to scan the entire cache when - * a large delta change is calculated directly. - */ - if (delta < freeable / 4) - total_scan =3D min(total_scan, freeable / 2); - - /* - * Avoid risking looping forever due to too large nr value: - * never try to free more than twice the estimate number of - * freeable entries. - */ - if (total_scan > freeable * 2) - total_scan =3D freeable * 2; + total_scan =3D min(total_scan, (2 * freeable)); =20 trace_mm_shrink_slab_start(shrinker, shrinkctl, nr, freeable, delta, total_scan, priority); @@ -744,10 +715,15 @@ static unsigned long do_shrink_slab(struct shrink_c= ontrol *shrinkctl, cond_resched(); } =20 - if (next_deferred >=3D scanned) - next_deferred -=3D scanned; - else - next_deferred =3D 0; + /* + * The deferred work is increased by any new work (delta) that wasn't + * done, decreased by old deferred work that was done now. + * + * And it is capped to two times of the freeable items. + */ + next_deferred =3D max_t(long, (nr + delta - scanned), 0); + next_deferred =3D min(next_deferred, (2 * freeable)); + /* * move the unused scan count back into the shrinker in a * manner that handles concurrent updates. --=20 2.26.2