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Tue, 06 Jan 2026 20:28:18 -0800 (PST) Received: from google.com ([2a00:79e0:2031:6:9f6a:2617:8891:93ff]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-34f5f7b1d81sm3584165a91.1.2026.01.06.20.28.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 06 Jan 2026 20:28:16 -0800 (PST) Date: Wed, 7 Jan 2026 13:28:11 +0900 From: Sergey Senozhatsky To: zhangdongdong Cc: Sergey Senozhatsky , Andrew Morton , Richard Chang , Minchan Kim , Brian Geffon , David Stevens , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-block@vger.kernel.org, Minchan Kim Subject: Re: [PATCHv2 1/7] zram: introduce compressed data writeback Message-ID: <7bnmkuodymm33yclp6e5oir2sqnqmpwlsb5qlxqyawszb5bvlu@l63wu3ckqihc> References: <20251201094754.4149975-1-senozhatsky@chromium.org> <20251201094754.4149975-2-senozhatsky@chromium.org> <40e38fa7-725b-407a-917a-59c5a76dedcb@sina.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <40e38fa7-725b-407a-917a-59c5a76dedcb@sina.com> X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 80FD4C0006 X-Stat-Signature: 5qzep176z15im1pqhz4d8e5oghaahfmd X-HE-Tag: 1767760099-982200 X-HE-Meta: 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 xiPPu8z3 m40Ikng3ij7CWnLycyM/d7gXsFWBE7z1k0CmiKq/c2cPVE3zHJPRyEotLjlVDgeDeOLDSIke4/V/BbtuR0UXo9RqQ9yqkk7VnZyghcdjZgXtbSI5Tx5Z5zWg5b7uoRE30HwHcgA0D0Sa1IryphBLk4qG4Bm/AazEgx42M6qQTJI/uRxjl2b5vX4ZYyhFvzSjJmUDFJofu3Whsyz5PLndX+oUGnnJxRDzJE7I7MpO0EuzVlL8r8x8h/pgI7NyqcwCejBe+8M8crbkJ+ENqvRLlYxAJGwF/kHTOnuhJ/GfY76j0cOaQNk+hm6tLg0nCV5fZ8u/27ph/J4Noy7I0jTxTHzQZ/51bjgjB+iKRRCxbCVa06jgz+Sgjp0JAR/FWSGhOFeQq 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 (26/01/07 11:50), zhangdongdong wrote: > Hi Sergey, > > Thanks for the work on decompression-on-demand. > > One concern I’d like to raise is the use of a workqueue for readback > decompression. In our measurements, deferring decompression to a worker > introduces non-trivial scheduling overhead, and under memory pressure > the added latency can be noticeable (tens of milliseconds in some cases). The problem is those bio completions happen in atomic context, and zram requires both compression and decompression to be non-atomic. And we can't do sync read on the zram side, because those bio-s are chained. So the current plan is to look how system hi-prio per-cpu workqueue will handle this. Did you try high priority workqueue?