[dm-devel] [PATCHES]: dm lock optimization
Mikulas Patocka
mpatocka at redhat.com
Thu Apr 19 03:03:33 UTC 2012
Hi
I placed dm lock optimization patches here
http://people.redhat.com/mpatocka/patches/kernel/dm-lock-optimization/
The patches remove cache-line bouncing from device mapper when multiple
processors submit requests simultaneously.
I was able to measure performance improvement, although in a very specific
setup (it is unmeasurable with normal disks).
The setup to measure it is:
- two quad-core Opterons
- use ramdisk as a block device, leave it empty
- create 11 nested dm-linear mappings on it (so that each i/o passes
through 11 levels of dm-linear and then goes to the ramdisk)
- run fio with 8 threads, using direct-io to read 512-byte blocks
(time fio --rw=randread --size=1G --bsrange=512-512 --direct=1
--filename=/dev/mapper/dm-test --name=job1 --name=job2 --name=job3
--name=job4 --name=job5 --name=job6 --name=job7 --name=job8)
With this setup it can be measured that the patches help:
no patch (3.3 kernel): 68.9s
patch 1: 64.3s
patch 1,2: 52.3s
patch 1,2,3: 45.2s
patch 1,2,3,4: 41.2s
patch 1,2,3,4,5: 34.0s
Mikulas
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