zcache preliminary benchmark results

From: Dan Magenheimer
Date: Wed Mar 21 2012 - 19:41:50 EST


Last November, in an LKML thread I would rather forget*, James
Bottomley and others asked for some benchmarking to be done for
zcache (among other things). For various reasons, that benchmarking
is just now getting underway and more will be done, but it might be
useful to publish some interesting preliminary results now.

Summary: On a kernel compile "make -jN" workload, with different
values of N to test varying memory pressure, zcache
shows no performance loss when memory pressure is low,
and up to 31% performance improvement when memory pressure
is moderate to high. RAMster does even better.

(Note that RAM is intentionally constrained to 1GB to force
memory pressure for higher N in the workload.)

* thread summarized in LWN (http://lwn.net/Articles/465317/)

=========

Benchmark results and description:

(all results in seconds so smaller is better)
N= nozcache zcache faster by RAMster faster by
4 879 877 0% 887 -1%
8 858 856 0% 866 -1%
12 858 856 0% 875 -2%
16 1009 922 9% 949 6%
20 1316 1154 14% 1162 13%
24 2164 1714 26% 1788 21%
28 3293 2500 31% 2177 51%
32 4286 4282 0% 3599 19%
36 6516 6602 -1% 5394 22%
40 DNC 13755 8172 68% (over zcache)

DNC=did not complete: stopped after 5 hours = 18000

Workload:
kernel compile "make -jN" with varying N
measurements in elapsed seconds
boot kernel: 3.2 + frontswap/ramster commits
Oracle Linux 6 distro with ext4
fresh reboot for each test run
all tests run as root in multi-user mode

Hardware:
Dell Optiplex 790 = ~$500 (two used for RAMster)
Intel Core i5-2400 @ 3.10 GHz, 4coreX2thread, 6M cache
1GB RAM DDR3 1333Mhz (for RAMster, other server has 8GB)
One 7200rpm SATA 6.0Gb/s drive with 8MB cache
10GB swap partition
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