path: root/mm/ksm.c
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authorTimofey Titovets <>2018-12-28 00:34:00 -0800
committerLinus Torvalds <>2018-12-28 12:11:46 -0800
commit0b9df58b79fa283fbedc0fb6a8e248599444bacc (patch)
treed75886dd9e92f76c3c24f9a812b9ead419daa389 /mm/ksm.c
parentd381c54760dcfad23743da40516e7e003d73952a (diff)
xxHash: create arch dependent 32/64-bit xxhash()
Patch series "Currently used jhash are slow enough and replace it allow as to make KSM", v8. Apeed (in kernel): ksm: crc32c hash() 12081 MB/s ksm: xxh64 hash() 8770 MB/s ksm: xxh32 hash() 4529 MB/s ksm: jhash2 hash() 1569 MB/s Sioh Lee's testing (copy from other mail): Test platform: openstack cloud platform (NEWTON version) Experiment node: openstack based cloud compute node (CPU: xeon E5-2620 v3, memory 64gb) VM: (2 VCPU, RAM 4GB, DISK 20GB) * 4 Linux kernel: 4.14 (latest version) KSM setup - sleep_millisecs: 200ms, pages_to_scan: 200 Experiment process: Firstly, we turn off KSM and launch 4 VMs. Then we turn on the KSM and measure the checksum computation time until full_scans become two. The experimental results (the experimental value is the average of the measured values) crc32c_intel: 1084.10ns crc32c (no hardware acceleration): 7012.51ns xxhash32: 2227.75ns xxhash64: 1413.16ns jhash2: 5128.30ns In summary, the result shows that crc32c_intel has advantages over all of the hash function used in the experiment. (decreased by 84.54% compared to crc32c, 78.86% compared to jhash2, 51.33% xxhash32, 23.28% compared to xxhash64) the results are similar to those of Timofey. But, use only xxhash for now, because for using crc32c, cryptoapi must be initialized first - that require some tricky solution to work good in all situations. So: - First patch implement compile time pickup of fastest implementation of xxhash for target platform. - The second patch replaces jhash2 with xxhash This patch (of 2): xxh32() - fast on both 32/64-bit platforms xxh64() - fast only on 64-bit platform Create xxhash() which will pick up the fastest version at compile time. Link: Signed-off-by: Timofey Titovets <> Reviewed-by: Pavel Tatashin <> Reviewed-by: Mike Rapoport <> Reviewed-by: Andrew Morton <> Cc: Andrea Arcangeli <> Cc: leesioh <> Signed-off-by: Andrew Morton <> Signed-off-by: Linus Torvalds <>
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