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Wed, 05 Nov 2025 07:25:20 -0800 (PST) Message-ID: <83d64478-d53c-441f-b5b4-55b5f1530a03@kernel.dk> Date: Wed, 5 Nov 2025 08:25:19 -0700 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3] zram: Implement multi-page write-back To: Yuwen Chen Cc: akpm@linux-foundation.org, bgeffon@google.com, licayy@outlook.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, liumartin@google.com, minchan@kernel.org, richardycc@google.com, senozhatsky@chromium.org References: Content-Language: en-US From: Jens Axboe In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 52E9F1C0016 X-Stat-Signature: xsrshc4zraerdaeaxicna768wa3fa367 X-Rspam-User: X-HE-Tag: 1762356322-112105 X-HE-Meta: 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 wAx3UOD/ jbl485ds3yVcs85RCroo8vHNlWvMR2Iwy0yd2DEIrPItncwFnaq3OqrbfBn9cSTSZ5BWqTSgjgSqGJioF+2kMoDHPNK/IhnaPmurBE8is6CEc1WrVA+05EvQTic0KRi0mp2v/Fc6jelcrjIL86ZlEXp2v293CGvzjpEr/DMFc1bsQqe+8aDmtkDoiMbsMskE5ZnpTeO3bJOncCURxoFafymIyfwvYom19BNV71dBX+fOw7g/mtxNJ0+4NvnFJRsxYshmlRt/HYDRkwO1mioeRQaB53NZFL7b1xM5Qw4dm8kPMsRUxu7hmTOYXRXAC/ZYuRek+02L1vvDExI2L6tIikBgPNINorGU1aBRPlL/yVJFRDPDuFl1s0NbpI45efVTGlIJ7XCUmvbZ9txNWRJjGr01bDf5GojvaGoJdSHhirdThSrfE8qHmsAWwEz/r9NXlxAoKXHjD917dSCUNQtRSzz5zaw== 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 11/4/25 11:48 PM, Yuwen Chen wrote: > For block devices, sequential write performance is significantly > better than random write. Currently, zram's write-back function > only supports single-page operations, which fails to leverage > the sequential write advantage and leads to suboptimal performance. > This patch implements multi-page batch write-back for zram to > leverage sequential write performance of block devices. > After applying this patch, a large number of pages being merged > into batch write operations can be observed via the following test > code, which effectively improves write-back performance. > > mount -t debugfs none /sys/kernel/debug/ > echo "block:block_bio_frontmerge" >> /sys/kernel/debug/tracing/set_event > echo "block:block_bio_backmerge" >> /sys/kernel/debug/tracing/set_event > cat /sys/kernel/debug/tracing/trace_pipe & > echo "page_indexes=1-10000" > /sys/block/zram0/writeback > > Signed-off-by: Yuwen Chen > Reviewed-by: Fengyu Lian > --- > Changes in v3: > - Postpone the page allocation. > Changes in v2: > - Rename some data structures. > - Fix an exception caused by accessing a null pointer. Please either finish the patch before sending it out, or take your time before posting again. Sending 3 versions in one day will just make people ignore you. This commit message is in dire need of some actual performance results. This is a change for better performance, no? If so, you should have some clear numbers in there describing where it's better, and where it's worse (if appropriate). -- Jens Axboe