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Wed, 29 Jan 2025 19:13:37 -0800 (PST) Received: from google.com ([2401:fa00:8f:203:d794:9e7a:5186:857e]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-21de32ed647sm3368245ad.133.2025.01.29.19.13.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 29 Jan 2025 19:13:36 -0800 (PST) Date: Thu, 30 Jan 2025 12:13:30 +0900 From: Sergey Senozhatsky To: Yosry Ahmed Cc: Sergey Senozhatsky , Andrew Morton , Minchan Kim , Johannes Weiner , Nhat Pham , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCHv1 0/6] zsmalloc: preemptible object mapping Message-ID: References: <20250129064853.2210753-1-senozhatsky@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: cjtny8x6xpioc7npqchuyzm5ogyngkb6 X-Rspam-User: X-Rspamd-Queue-Id: 7B69C160002 X-Rspamd-Server: rspam03 X-HE-Tag: 1738206818-200517 X-HE-Meta: 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 potNHfuD xqv+CI1D6IE5uMw3g2ZVxm+yt+KOzAQTcpk6Hw8CrOAFJnCeHrCyxEZlA/KfUnBCSZPFNk97GQDM2etgDx/GfK2dgzb5m8Z8vDkuPDl86nYm8F378ewAjx3JWgt1r/ix2AkKIEbQ+Nq9Jrz6HS12qWonCm5yph8GYC23l9S6gShvwwiIzzvwKGHt0xZjPA1PxqMMXwjp/nRHHmjMET4PVRoVW3tIThoFyCgOq7tund4YF3araGRf10lejLCt6TRVppxeSA8PpsoJp4Z7vNcq8snaNK6ds1hHyVt0mFk7trF8qHgZYpQXWLHJLUpnDFa/ilPjKsNToaxhohWAZd5J6SIxpH+0BEzaJSVWmMeouyDdQ8yPje11R+i8Q9Q== X-Bogosity: Ham, tests=bogofilter, spamicity=0.006555, 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 (25/01/29 15:53), Yosry Ahmed wrote: > On Wed, Jan 29, 2025 at 03:43:46PM +0900, Sergey Senozhatsky wrote: > > This is Part II of the series [1] that makes zram read() and write() > > preemptible. This part focuses only zsmalloc because zsmalloc imposes > > atomicity restrictions on its users. One notable example is object > > mapping API, which returns with: > > a) local CPU lock held > > b) zspage rwlock held > > > > First, zsmalloc is converted to use sleepable RW-"lock" (it's atomic_t > > in fact) for zspage migration protection. Second, a new handle mapping > > is introduced which doesn't use per-CPU buffers (and hence no local CPU > > lock), does fewer memcpy() calls, but requires users to provide a > > pointer to temp buffer for object copy-in (when needed). Third, zram is > > converted to the new zsmalloc mapping API and thus zram read() becomes > > preemptible. > > > > [1] https://lore.kernel.org/linux-mm/20250127072932.1289973-1-senozhatsky@chromium.org > > > > RFC -> v1: > > - Only zspage->lock (leaf-lock for zs_map_object()) is converted > > to a preemptible lock. The rest of the zspool locks remain the > > same (Yosry hated with passion the fact that in RFC series all > > zspool looks would become preemptible). > > Hated is a big word here, I was merely concerned about how the locking > changes would affect performance :P Yeah I'm just messing around :)