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Wed, 08 Nov 2023 00:03:22 -0800 (PST) MIME-Version: 1.0 References: <20231107215742.363031-1-ankur.a.arora@oracle.com> <20231107230822.371443-1-ankur.a.arora@oracle.com> <20231107230822.371443-12-ankur.a.arora@oracle.com> <20231108012823.GD11577@google.com> <7155f21f-a7e5-cc36-89e5-c1ce257b9420@suse.cz> In-Reply-To: <7155f21f-a7e5-cc36-89e5-c1ce257b9420@suse.cz> From: Yosry Ahmed Date: Wed, 8 Nov 2023 00:02:46 -0800 Message-ID: Subject: Re: [RFC PATCH 68/86] treewide: mm: remove cond_resched() To: Vlastimil Babka Cc: Sergey Senozhatsky , Ankur Arora , linux-kernel@vger.kernel.org, tglx@linutronix.de, peterz@infradead.org, torvalds@linux-foundation.org, paulmck@kernel.org, linux-mm@kvack.org, x86@kernel.org, akpm@linux-foundation.org, luto@kernel.org, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, willy@infradead.org, mgorman@suse.de, jon.grimm@amd.com, bharata@amd.com, raghavendra.kt@amd.com, boris.ostrovsky@oracle.com, konrad.wilk@oracle.com, jgross@suse.com, andrew.cooper3@citrix.com, mingo@kernel.org, bristot@kernel.org, mathieu.desnoyers@efficios.com, geert@linux-m68k.org, glaubitz@physik.fu-berlin.de, anton.ivanov@cambridgegreys.com, mattst88@gmail.com, krypton@ulrich-teichert.org, rostedt@goodmis.org, David.Laight@aculab.com, richard@nod.at, mjguzik@gmail.com, SeongJae Park , Mike Kravetz , Muchun Song , Andrey Ryabinin , Marco Elver , Catalin Marinas , Johannes Weiner , Michal Hocko , Roman Gushchin , Shakeel Butt , Naoya Horiguchi , Miaohe Lin , David Hildenbrand , Oscar Salvador , Mike Rapoport , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Dennis Zhou , Tejun Heo , Christoph Lameter , Hugh Dickins , Pekka Enberg , David Rientjes , Joonsoo Kim , Vitaly Wool , Minchan Kim , Seth Jennings , Dan Streetman Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: sjt3igi3yasodewojnwaaur79biegrxs X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 2C65A180010 X-Rspam-User: X-HE-Tag: 1699430605-63972 X-HE-Meta: U2FsdGVkX1+3tKY0wq/dmw3EICrEIAHZ4/G2Fn68bxgFtiXmYGdt3KbMhnRvW2szKlNTXA5+TVWrMJ8adwGnwncnFwM3Ro+ybLvkJ3v157DLTJ9cKwtk3oG1YeYEQTzr9QLnu/vlnp9sWOaEWvIEBrDDz7qHT+6gchqvkODAz8KGteKzeNfGAP7K599eu9Zk3lstnJyVSfiCscQH7lQyHeFeli11fT4PDPxpLyBGe8puslNjREMS4SGl51cXa1PSMp361Mvv9jqsIFrkl8I2aNB9oj5LQd0XIwXUffeUrbjprQqFXVTzS9pg71k0/6pYWTOoJFiChEGRw0/NJ+MP+O9akNWeBKQwWHU968wxp9CGURWDlTAwBBq7xUkOl9mnjCsIGWxfSizIia81U1t9dKo5xzsGLkxge0MCrozhBekR/GwtGXSbLAfjQ3FC1DrGhAfkb/8Nlk60q8SttcFXk/Iy8N9IBVAOC9KJoRCwpsqWkccVSubPwMsbKbu0+1xj3zevyXjddMuFL3VhE8Tpu603ePdmmVJToerGkpYT6qroQMJ4sRqtPSZPkIX6pHF6XqRyFQl3fjMw7n3iFPzM3sVS3hB5A1N5s8RLwg0Vi49oXm+Y4D8h4mkNwRB8rj0vM332u9dTQZ2mOg8xzV/p94LkicHB6RLq4MRcJl9lRfRQue0Zvgg6uI41ro6SUumDr0rofHVuXAXjTKRHF7gfBE/mXBuSiSxtUlkjX31eYLUOzHsxJpjMEGV05u3UKOPizutuBxx4082M/yEvUoG5vu4eTlyIy2+pJ1TVvxG9rc4ERTQ/rTxbQtmwjZwXvMlTi5bW6lXKdwlPB8/i6sIjBVA24Kw9U/hfym5jCleFcInc+tHeqlsfbsKOecNiY0RV7ydbsP7F3gi4Wb439eOB5hA2rthUlPenSvIkplqGtxtKiQIxDU6WqrAGDyXerATDic1nRyNcePkHVkPzwE+ 8qF0veH4 BI5TpU/G/kCLsv059C5Ajx5h6PYQksVlMHW/ZO+MXPr+NwLWBBKMqF3fkyTD6qnB0KE62C6o2bNQg+8hy3+otMBEr14XBbnWnitL6GbrAkYfaiCWQ+7O8zj/ON6GMYO0V4EPID0Uk652LExJOyUCKTBIdS+nc2F95TxFMqUohuOGE1cVp1TroxnQznDEny/d01gEMmZBRtfuqatHDmn6ktPUG5BHD+zGQ2Dzt2M98/lrD2q9UvztokBW2MDtaEkUC3Ix7pE2eNE8A8OBgPDM+Y/XPe6kUGcG5aiS4Kb5odHW+UwGSZfx67RmwV9mGixzRTRnrzG2MOQIe6vWf00kRF8RFiQ== 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: List-Subscribe: List-Unsubscribe: On Tue, Nov 7, 2023 at 11:49=E2=80=AFPM Vlastimil Babka wr= ote: > > On 11/8/23 02:28, Sergey Senozhatsky wrote: > > On (23/11/07 15:08), Ankur Arora wrote: > > [..] > >> +++ b/mm/zsmalloc.c > >> @@ -2029,7 +2029,6 @@ static unsigned long __zs_compact(struct zs_pool= *pool, > >> dst_zspage =3D NULL; > >> > >> spin_unlock(&pool->lock); > >> - cond_resched(); > >> spin_lock(&pool->lock); > >> } > >> } > > > > I'd personally prefer to have a comment explaining why we do that > > spin_unlock/spin_lock sequence, which may look confusing to people. > > Wonder if it would make sense to have a lock operation that does the > unlock/lock as a self-documenting thing, and maybe could also be optimize= d > to first check if there's a actually a need for it (because TIF_NEED_RESC= HED > or lock is contended). +1, I was going to suggest this as well. It can be extended to other locking types that disable preemption as well like RCU. Something like spin_lock_relax() or something. > > > Maybe would make sense to put a nice comment in all similar cases. > > For instance: > > > > rcu_read_unlock(); > > - cond_resched(); > > rcu_read_lock(); > >