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16ac982064
5.4 kernel defaults to lzo-rle for zram. lzo-rle added run-length encoding for lzo, which is beneficial to the use case of zram that often has long runs of zero bytes. However, according to my testing results, lzo-rle still has lower decompression throughput and higher access latency compared to lz4. lzo-rle beats lz4 in compression ratio, but most Xiaomi SM8350 devices have either 8GB or 12GB of RAM where memory pressure hardly happens. Therefore, lz4's higher throughput and lower latency is more preferable. Now that I added LZ4_FAST_DEC_LOOP to the kernel lz4 module from upstream lz4 1.9.x release, the decompression speed has increased by another 10%, which leads further ahead lzo-rle. Test setup: - Disable swap on zram if it is enabled $ swapoff /dev/block/zram0 - If you want to change the comp_algorithm after zram has been initialized, reset zram first. $ echo 1 > /sys/block/zram0/reset - Set the comp_algorithm. For example, for lz4 $ echo lz4 > /sys/block/zram0/comp_algorithm - Set up zram size $ echo 4294967296 > /sys/block/zram0/disksize - Make the swap $ mkswap /dev/block/zram0 - Pre-fill zram with 1GB of real-word zram data dumped previously under memory pressure. For example, $ dd if=/sdcard/zram.test of=/dev/block/zram0 bs=1m count=1000 Random 4k read: $ fio --readonly --name=randread --direct=1 --rw=randread --ioengine=psync \ --randrepeat=0 --numjobs=4 --iodepth=1 --group_reporting=1 \ --filename=/dev/block/zram0 --bs=4K --size=1000M lzo-rle: read: IOPS=1547k, BW=6042MiB/s (6336MB/s)(4000MiB/662msec) lz4: read: IOPS=1646k, BW=6431MiB/s (6743MB/s)(4000MiB/622msec) lz4 fast dec: read: IOPS=1775k, BW=6932MiB/s (7269MB/s)(4000MiB/577msec) Sequencial 4k read: $ fio --readonly --name=zram_seqread --direct=1 --rw=read --ioengine=psync \ --numjobs=4 --iodepth=1 --group_reporting=1 --filename=/dev/block/zram0 \ --bs=4K --size=1000M lzo-rle: read: IOPS=1816k, BW=7092MiB/s (7437MB/s)(4000MiB/564msec) lz4: read: IOPS=1907k, BW=7449MiB/s (7811MB/s)(4000MiB/537msec) lz4 fast dec: read: IOPS=2004k, BW=7828MiB/s (8208MB/s)(4000MiB/511msec) Compression ratio from /sys/block/zram0/mm_stat lzo-rle: 1048576000 -> 81969152 lz4: 1048576000 -> 86200320 zstd was also considered. It offers really nice compression ratio, 1048576000 -> 59899904, but the throughput and latency are so much worse than lz4 and lzo-rle. It is probably more suitable for traditional desktop/server swap setup with less aggressive swappiness value. It can also help alleviate high memory pressure situation by compressing the RAM to smaller size. |
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| configs | ||
| keylayout | ||
| libqti-perfd-client | ||
| light | ||
| overlay | ||
| overlay-pe/frameworks/base/core/res/res/values | ||
| permissions | ||
| pocketmode | ||
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| rro_overlays | ||
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| wifi | ||
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| BoardConfigCommon.mk | ||
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| extract-files.sh | ||
| generate_sha1_from_commit.sh | ||
| LICENSE | ||
| manifest.xml | ||
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| proprietary-files.txt | ||
| releasetools.py | ||
| reorder-libs.py | ||
| sdm710.mk | ||
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| update-sha1sums.py | ||
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