Ric Wheeler wrote:
Theodore Tso wrote:
On Thu, Aug 28, 2008 at 09:40:30AM -0400, Ric Wheeler wrote:
I can try and test this with my fsync() heavy fs_mark run...
Given [1] I have no doubt that you should see a difference between
mke2fs from e2fsprogs 1.41.0 (which will allocate the journal at the
beginning of the filesystem) and the latest tip of e2fsprogs.
It would be interesting to see how measurable the difference is,
though. I'd recommend doing "mke2fs -t ext4dev" using both versions
of mke2fs, and seeing how much the difference it makes.
[1]
http://www.usenix.org/events/usenix05/tech/general/full_papers/prabhakaran/prabhakaran_html/main.html#fig-journal-location-withinfs-fix
- Ted
I was thinking of trying this on a much larger disk (1TB) - the
article reports on a 4GB partition which is pretty tiny,
ric
Using Ted's new journal in the middle mkfs & hacking it slightly to make
the journal go back to block 0, I ran some quick tests to try and
measure an impact of the journal placement (multiple threads writing 4MB
files).
The results that are most clear are certainly that delayed allocation is
a big win, the journal placement has mostly a positive impact on the
write performance, but the results are quite close.
Starting with a newly created file system, each pass put down 16,000 4MB
files:
Count Files/sec - ZERO Files/sec - Middle
16000 20.8 20.8
32000 19.2 18.4
48000 16.0 14.4
64000 20.8 20.8
80000 20.8 20.8
96000 20.8 20.8
112000 20.8 20.8
128000 19.2 20.8
144000 19.2 19.2
160000 17.6 19.2
176000 16.6 17.6
192000 16.0 16.0
208000 14.4 14.4
224000 12.8 14.4
With no delayed allocation:
Count Files/sec - ZERO Files/sec - Middle
16000 16.0 16.0
32000 16.0 16.0
48000 16.0 16.0
64000 16.0 14.8
80000 14.4 14.4
96000 14.1 14.4
112000 12.8 12.8
128000 11.2 11.2
144000 11.2 12.8
160000 14.4 14.4
176000 11.3 12.8
192000 14.9 12.8
208000 16.0 16.0
224000 14.4 16.0
ric
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