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Tue, 24 Jan 2023 23:36:09 -0800 (PST) X-Google-Smtp-Source: AMrXdXv6r5ehrqKjuOqxpudgJdHfNcykat5kT9ZAeiiKrUzWSSAJYK3YalJM5sJ2WYW3DmqLUhiPTw== X-Received: by 2002:a05:6870:e0ce:b0:15f:3bb9:7b3d with SMTP id a14-20020a056870e0ce00b0015f3bb97b3dmr17462978oab.28.1674632169128; Tue, 24 Jan 2023 23:36:09 -0800 (PST) Received: from LeoBras.redhat.com ([2804:1b3:a800:14fa:9361:c141:6c70:c877]) by smtp.gmail.com with ESMTPSA id x189-20020a4a41c6000000b0050dc79bb80esm1538802ooa.27.2023.01.24.23.36.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 24 Jan 2023 23:36:08 -0800 (PST) From: Leonardo Bras To: Johannes Weiner , Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Andrew Morton , Marcelo Tosatti Cc: Leonardo Bras , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 5/5] mm/memcontrol: Remove flags from memcg_stock_pcp Date: Wed, 25 Jan 2023 04:35:02 -0300 Message-Id: <20230125073502.743446-6-leobras@redhat.com> X-Mailer: git-send-email 2.39.1 In-Reply-To: <20230125073502.743446-1-leobras@redhat.com> References: <20230125073502.743446-1-leobras@redhat.com> MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-Rspamd-Queue-Id: C8BCE100009 X-Rspamd-Server: rspam09 X-Rspam-User: X-Stat-Signature: qwh664b84izz5yjdeibr46b9p1efddtu X-HE-Tag: 1674632176-927905 X-HE-Meta: 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 znQjm3QW z9P0lLElD/D3r5rQ1d/GWuP9WeBg7JKL7sJq7vxHauPKlH24T7F8b5c7RPm8AahWIKEzz0DBQPFa/XRb4/uch0SxPx+ya78eTwAlc4UqdpWlxXrnmRKZoWsVOI8k4l++xp8dQFEqimHG98wX5jlVvaGv/WzMwhiXXNzSgwXWt1s1bTO4PBABm5vcGs3jznQ52f2Sf3h7z86aljVeFErzsDiNqiowzudBZlYbSB2z0naD+rRmYRVjc3Tq3XlKi5lIUtNX9CFMayWAVDkDwAX2X2yHP/0oLSVm0bDCzkFm96JA8e4EEZP2VnslaZi/Lx3LgVY/I+uUgFuPoMD/zgKcbmfpyYCcqjiYmreZZrSkTnvQ1L7OgGrw6ww2yZsls2GwMCIaCIltdM54iXypj2+BhdkNb7sSuKcFLGriKS1YQE4HASVoqERCQnuybtvX6xgC7ORmsaEqapbNTr1OPTBMigaZ7eVlg8pCkShZG X-Bogosity: Ham, tests=bogofilter, spamicity=0.000006, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: The flags member of struct memcg_stock_pcp has only one used bit: FLUSHING_CACHED_CHARGE Both struct member and flag were created to avoid scheduling multiple instances of kworkers running drain_local_stock() for a single cpu. How could this scenario happen before: - drain_all_stock() gets called, get ownership of percpu_charge_mutex, schedules a drain_local_stock() on cpu X, and drops ownership of percpu_charge_mutex. - Another thread calls drain_all_stock(), get ownership of percpu_charge_mutex, schedules a drain_local_stock() on cpu X, ... Since the stock draining is now performed by the thread running drain_all_stock(), and happens before letting go of the percpu_charge_mutex, there is no chance of another drain happening between test_and_set_bit() and clear_bit(), so flags is now useless. Remove the flags member of memcg_stock_pcp, its usages and the FLUSHING_CACHED_CHARGE define. Signed-off-by: Leonardo Bras --- mm/memcontrol.c | 7 +------ 1 file changed, 1 insertion(+), 6 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 5b7f7c2e0232f..60712f69595e4 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2183,9 +2183,6 @@ struct memcg_stock_pcp { int nr_slab_reclaimable_b; int nr_slab_unreclaimable_b; #endif - - unsigned long flags; -#define FLUSHING_CACHED_CHARGE 0 }; static DEFINE_PER_CPU_SHARED_ALIGNED(struct memcg_stock_pcp, memcg_stock) = { @@ -2281,7 +2278,6 @@ static void drain_stock_from(struct memcg_stock_pcp *stock) old = drain_obj_stock(stock); drain_stock(stock); - clear_bit(FLUSHING_CACHED_CHARGE, &stock->flags); spin_unlock_irqrestore(&stock->stock_lock, flags); if (old) @@ -2351,8 +2347,7 @@ static void drain_all_stock(struct mem_cgroup *root_memcg) flush = true; rcu_read_unlock(); - if (flush && - !test_and_set_bit(FLUSHING_CACHED_CHARGE, &stock->flags)) + if (flush) drain_stock_from(stock); } migrate_enable();