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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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: 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