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Thu, 12 Mar 2026 20:00:34 -0700 (PDT) Received: from google.com ([2a00:79e0:2031:6:ae8d:6319:a485:ec00]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2aece8098f7sm4469395ad.62.2026.03.12.20.00.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 12 Mar 2026 20:00:34 -0700 (PDT) Date: Fri, 13 Mar 2026 12:00:30 +0900 From: Sergey Senozhatsky To: Andrew Morton , gao xu Cc: Sergey Senozhatsky , Minchan Kim , Jens Axboe , "linux-block@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "surenb@google.com" , zhouxiaolong Subject: Re: [PATCH v2] zram: Optimize LZ4 dictionary compression performance Message-ID: References: <698181478c9c4b10aa21b4a847bdc706@honor.com> Precedence: bulk X-Mailing-List: linux-block@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: <698181478c9c4b10aa21b4a847bdc706@honor.com> On (26/03/13 02:41), gao xu wrote: > Calling `LZ4_loadDict()` repeatedly in Zram causes significant overhead > due to its internal dictionary pre-processing. This commit introduces a > template stream mechanism to pre-process the dictionary only once when > the dictionary is initially set or modified. It then efficiently copies > this state for subsequent compressions. > > Verification Test Items: > Test Platform: android16-6.12 > 1. Collect Anonymous Page Dataset > 1) Apply the following patch: > static bool zram_meta_alloc(struct zram *zram, u64 disksize) > if (!huge_class_size) > - huge_class_size = zs_huge_class_size(zram->mem_pool); > + huge_class_size = 0; > 2）Install multiple apps and monkey testing until SwapFree is close to 0. > 3）Execute the following command to export data: > dd if=/dev/block/zram0 of=/data/samples/zram_dump.img bs=4K > > 2. Train Dictionary > Since LZ4 does not have a dedicated dictionary training tool, the zstd > tool can be used for training[1]. The command is as follows: > zstd --train /data/samples/* --split=4096 --maxdict=64KB -o /vendor/etc/dict_data > > 3. Test Code > adb shell "dd if=/data/samples/zram_dump.img of=/dev/test_pattern bs=4096 count=131072 conv=fsync" > adb shell "swapoff /dev/block/zram0" > adb shell "echo 1 > /sys/block/zram0/reset" > adb shell "echo lz4 > /sys/block/zram0/comp_algorithm" > adb shell "echo dict=/vendor/etc/dict_data > /sys/block/zram0/algorithm_params" > adb shell "echo 6G > /sys/block/zram0/disksize" > echo "Start Compression" > adb shell "taskset 80 dd if=/dev/test_pattern of=/dev/block/zram0 bs=4096 count=131072 conv=fsync" > echo. > echo "Start Decompression" > adb shell "taskset 80 dd if=/dev/block/zram0 of=/dev/output_result bs=4096 count=131072 conv=fsync" > echo "mm_stat:" > adb shell "cat /sys/block/zram0/mm_stat" > echo. > Note: To ensure stable test results, it is best to lock the CPU frequency > before executing the test. > > LZ4 supports dictionaries up to 64KB. Below are the test results for > compression rates at various dictionary sizes: > dict_size base patch > 4 KB 156M/s 219M/s > 8 KB 136M/s 217M/s > 16KB 98M/s 214M/s > 32KB 66M/s 225M/s > 64KB 38M/s 224M/s > > When an LZ4 compression dictionary is enabled, compression speed is > negatively impacted by the dictionary's size; larger dictionaries result > in slower compression. This patch eliminates the influence of dictionary > size on compression speed, ensuring consistent performance regardless of > dictionary scale. > > [1] https://github.com/lz4/lz4?tab=readme-ov-file > > Signed-off-by: gao xu Acked-by: Sergey Senozhatsky