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Thu, 15 Oct 2026 20:13:44 -0700 (PDT) Received: from google.com ([2a00:79e0:2031:6:a579:8b87:8304:7ac2]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-89f54b2eec9sm406056b3a.8.2026.10.15.20.13.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 15 Oct 2026 20:13:42 -0700 (PDT) Date: Fri, 16 Oct 2026 12:13:39 +0900 From: Sergey Senozhatsky To: Barry Song Cc: Sergey Senozhatsky , Bo Zhang , akpm@linux-foundation.org, bgeffon@google.com, minchan@kernel.org, richardycc@google.com, linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v3 10/11] zram: use rw_semaphore for decompression streams Message-ID: References: <20261015112440.1491168-1-zhangbo56@xiaomi.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: 8ieoffcfngqdeyftbb4199eddmb56zps X-Rspam-User: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: C2C41180003 X-HE-Tag: 1792120425-413994 X-HE-Meta: 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 QueVHDGK 1FAtmtMycEUuRHz2jdgSqwNA+ls3SJhgLrSUmZY8UhRSOaWfYgmPlL5Q+pyf2v6ggKN1zkKMyTSNDZRPmbwTiAcxY1LHffZtLZqAwE9O5TGGeJwZQn/pfuzMffnu8Ly7JI1RefBuktFvvDOBMso/FTnvM8S3AlNSw3703j3GLtr7k07rd4081928pyJXAEHjecXwarPpQ0RchSnT06REC6Y0V36FwyGFZMpJCwdEif9OOi6TyivMX1lpBoa3hy8FxkKnag4bxyODjU8Q9EiP+iPvfhSGjFalkLj0wmCmiKSpnqxHhcFQGqTYP5KdWP+fzDXeIV1FtAPXEb/ajPL6eDgINaz4zzQfMnK/NNEarRCNmPhyiytDCs5X2AjtJyLnh2c/MczDTf1eA+GxiklFtv5wavTDYae3ntoQGudsJbmoH/tQ= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi, On (26/10/16 11:10), Barry Song wrote: > > > I applied the kmalloc+memcpy variant on-device and re-ran the same > > > Android A/B. It removes the exclusive path entirely in our workload. > > > > > > 9+10 9+10 + kmalloc fastpath > > > read contended ~1,959 0 > > > read wait_ns total ~12 s 0 > > > read wait_ns max 72-96 ms 0 > > > shared 76.7% 100% > > > exclusive 23.3% 0% > > > dpin_contended 0 0 > > > > > > Every decompression now takes the shared (down_read) path, including the > > > cross-page objects that previously had to go exclusive. The ~1,959 > > > residual contentions on the exclusive path are gone, and pin contention > > > stays at zero, so the full read side runs concurrently with no stream > > > contention. > > > > > > Read-side contention end to end: > > > > > > baseline 9+10 9+10 + kmalloc > > > read contended 24,749 ~1,959 0 > > > shared 0% 76.7% 100% > > > > Thank you. I'll include kmalloc patch to v4 of the series. > > Hi Sergey, Bo, > > I assume when Sergey sent v4, could tag for the patchset with > > Tested-by: Bo Zhang That would be great. > also, Bo's data can be put in cover-letter? Sure, I can include it, along with my numbers.