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[73.93.239.127]) by smtp.gmail.com with ESMTPSA id 124sm3498648pfd.59.2021.01.27.15.34.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 27 Jan 2021 15:34:15 -0800 (PST) From: Yang Shi To: guro@fb.com, ktkhai@virtuozzo.com, 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: [v5 PATCH 11/11] mm: vmscan: shrink deferred objects proportional to priority Date: Wed, 27 Jan 2021 15:33:45 -0800 Message-Id: <20210127233345.339910-12-shy828301@gmail.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20210127233345.339910-1-shy828301@gmail.com> References: <20210127233345.339910-1-shy828301@gmail.com> MIME-Version: 1.0 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 workingset. So shrink deferred objects proportional to priority and cap nr_deferred t= o twice of cache items. The idea is borrowed fron 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, no regression i= s spotted so far. But it still may have regression for some corner cases. Signed-off-by: Yang Shi --- mm/vmscan.c | 40 +++++----------------------------------- 1 file changed, 5 insertions(+), 35 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 55ad91a26ba3..471d037d735e 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -662,7 +662,6 @@ static unsigned long do_shrink_slab(struct shrink_con= trol *shrinkctl, */ nr =3D count_nr_deferred(shrinker, shrinkctl); =20 - total_scan =3D nr; if (shrinker->seeks) { delta =3D freeable >> priority; delta *=3D 4; @@ -676,37 +675,9 @@ 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); @@ -745,10 +716,9 @@ static unsigned long do_shrink_slab(struct shrink_co= ntrol *shrinkctl, cond_resched(); } =20 - if (next_deferred >=3D scanned) - next_deferred -=3D scanned; - else - next_deferred =3D 0; + next_deferred =3D max_t(long, (nr - scanned), 0) + total_scan; + 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