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Tue, 06 Oct 2026 02:52:30 -0700 (PDT) Received: from google.com ([2a00:79e0:2031:6:ed0f:30a2:6c81:a58e]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-88b0d152432sm4523788b3a.53.2026.10.06.02.52.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 06 Oct 2026 02:52:29 -0700 (PDT) Date: Tue, 6 Oct 2026 18:52:24 +0900 From: Sergey Senozhatsky To: Nhat Pham Cc: Usama Arif , Andrew Morton , chengming.zhou@linux.dev, dsterba@suse.com, hannes@cmpxchg.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, terrelln@fb.com, yosry@kernel.org, riel@surriel.com, shakeel.butt@linux.dev, alex@ghiti.fr, senozhatsky@chromium.org, kernel-team@meta.com Subject: Re: [PATCH 1/2] mm: zswap: use separate compression and decompression requests Message-ID: References: <20261006002307.2669023-1-usama.arif@linux.dev> <20261006002307.2669023-2-usama.arif@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 9D0ABA0004 X-Rspam-User: X-Stat-Signature: 8xnz18qrm6ek939w5s7girn7tha35h7c X-HE-Tag: 1791280351-499514 X-HE-Meta: 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 q4HsOoke gnquRDWQfKx2eYOuJXCGtnxSJ+KCvis9Rg+Br4B8VXYvc9XBf1EC983ikSvUUn3GvX/gSok8jvqvV3iNHGdU3dnuOZJ+Ug26cDwdqMb1TyKdUlzPEINgiq+FtZpmClxzpJzTNXG2RwH3cQeKyJRkcO5eaNSSKPy/70FJ8KOvHIJo6bcSU3lS95hQ9MR0xeiQo8yc8OgdWXmeYgjBrcPoFU2r3tH8EZtVIPFM+kvPYA83dPlDt6p0LVMicPyWQMU0GfauThw4Dxuz/dm8MzgrrDm4Raq5Tf755j6ochnVNjoJmYFzYPDMheqm6fkDE/++g0NC5AFVx20Yi098CyxtsuyEUzrC3t1+kwYjdxLkNjoj8WRdLEVqvbLROt7QC9yFyGJCB Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On (26/10/06 11:47), Nhat Pham wrote: > On Tue, Oct 6, 2026 at 2:23 AM Usama Arif wrote: > > > > Stores and loads serialize on the same per-CPU acomp request and mutex. > > A low-priority store can be preempted as soon as the compressor drops > > its stream lock, while it still holds the mutex. A higher-priority load > > on that CPU then waits until the store runs again, which can take a > > long time when other tasks are runnable. > > > > Give compression and decompression their own request, completion wait > > and mutex. Since commit e2c3b6b21c77f ("mm: zswap: use SG list > > decompression APIs from zsmalloc"), the per-CPU buffer is only used for > > compression. The two requests can share the per-CPU transform: no > > in-tree implementation modifies transform state while (de)compressing, > > and shared codec state has its own locking. Loads can still wait for > > each other on the decompression mutex, and stores still serialize on > > the compression mutex. > > > > This follows the proposal from Sergey Senozhatsky for the same split > > for zram [1]. > > Thanks, zram peeps :P :D