Steve French wrote:
I have been looking at and testing Shaggy's cifs writepages patches,
and they look promising.
From my fastest test client to a laptop running Windows XP as a test
server (unfortunately this means running against a relatively slow
disk, but the file size should fit in cache on the server) here are
some initial results (at least three runs at each size). Doing large
file copy (dd if=/dev/zero bs=16K count=4K of =/mnt/testfile) of 64Mbytes
Over 100Mbit Ethernet
w/o the patch (writes will go 4K): 6.1 MB/sec
w/patch and wsize 16K (default) 8.8MB/sec
w/patch and wsize reduced to 4K 6.3MB/sec
w/patch and wsize 8K 8.5 MB/sec
w/patch and wsize increased to 32K 9.8 MB/sec
So over 100Mbit interface, increasing the write size on the wire, is
more than a 60% improvement, getting to about 3/4 of the maximum speed
the interface could sustain.
Over Gigabit (same machines)
w/o the patch (writes 4K): 11.7 MB/sec
w/patch and wsize 16K (default): 24MB/sec average (best run 38.8
MB/sec)
w/patch and wsize 32K: 41 MB/sec average (best run 52 MB/sec)
w/patch and wsize 36K: 38 MB/sec (best run 43.5)
w/patch and wsize 40K was somewhat slower than 36K
w/patch and wsize 53K performance was catostrophically slower
(1/10th the performance or less)
The wsize is limited to 13 pages at the moment due to the size of kvecs
(13 + 1 for the header = 14) used on sock_sendmsg
To get wsize of 32K to performan better than 16K wsize, the sk->sndbuf
for the socket had to be set above the default (16K) - my experiments
had sndbuf at just over 100K but sndbuf probably only needs to be
slightly more than twice the wsize (as nfs sunrpc does). I was
surprised that performance collapsed at relatively small wsize,
especially since Windows typically uses a write size of 60K. I did
some experiments over loopback interface to Samba server on the same
host, which showed problems with large write sizes as well. More
investigation is needed.
These initial results are promising, but it is still puzzling why write
sizes over 32K performed worse, and over 40K performed much worse.
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