[linux-mm-cc] compcache performance data
John Mitchell
johnlmitchell at gmail.com
Thu Jun 11 18:34:28 EDT 2009
Hi! I've recently started working with compcache, and have a few questions
in addition to a little data to contribute.
- what's the "sweet spot" for which compcache is most appropriate?
I've read about using this for netbooks, where CPU is relatively free, it
has limited memory, and disk is at a premium.
- for this sweet spot, what's the best test load, to measure performance?
How can this be made repeatable?
The wiki mentions "load Firefox, OpenOffice, and 3 evince windows", but that
doesn't sound very repeatable. The "scan" benchmark is very easy to use and
is repeatable, but how comparable is it to real-world information?
For my tests, I ran three configurations of swap: traditional swap to disk,
compcache only, and compcache with disk as backing store. The plot is
linked below, and I'm happy to publish data & scripts if that is useful. I
found that using compcache completed the workload quite a bit faster than
just with disk-based swap, and compcache+backing store was faster.
However, I realized that the numbers can be *very* specific to differing
sizes of RAM, compcache, swap disk, and workload. Nor do I trust that
"swapping is faster" is a concrete metric to optimize.
** How can I tune my system and load to best get results from compcache?
For a VM, how much 1) RAM, 2) swap disk, and 3) how much compcache
allocation? What's the test load?
Thanks so much!
- john
Testing done under Linux VM (KVM), compcache-0.5.3
- VM details:
. 128 MiB RAM, swap: ~152 MiB
. 1 CPU, QEMU 0.9.1
. Ubuntu 9.04 (kernel 2.6.28-11-generic)
. disk ~20 MB.sec buffered disk reads ("hdparm -Tt")
- Host details:
. Intel(R) Core(TM)2 CPU 6600 @ 2.40GHz
. Ubuntu 9.04 (kernel 2.6.28-11-generic)
Testing details
- full boot, runlevel 5
- run "scan 152 2" (ie allocate 152MiB and scan twice)
- run above test once for: disk based swap, ramzswap, and ramzswap with
backing store
http://www.flickr.com/photos/shavenwarthog/3618101530/
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