Currently used jhash are slow enough and replace it allow as to make KSM
less cpu hungry.
About speed (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
By sioh Lee tests (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.
So:
- Fisrt patch implement compile time pickup of fastest implementation of xxhash
for target platform.
- Second implement logic in ksm, what test speed of hashes and pickup fastest hash
Thanks.
CC: Andrea Arcangeli <aarcange@xxxxxxxxxx>
CC: linux-mm@xxxxxxxxx
CC: kvm@xxxxxxxxxxxxxxx
CC: leesioh <solee@xxxxxxxxxxxxxx>
Timofey Titovets (2):
xxHash: create arch dependent 32/64-bit xxhash()
ksm: replace jhash2 with faster hash
include/linux/xxhash.h | 23 +++++++++++++
mm/Kconfig | 2 ++
mm/ksm.c | 93 +++++++++++++++++++++++++++++++++++++++++++++++---
3 files changed, 114 insertions(+), 4 deletions(-)
--
2.14.1
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