On Tue, Dec 30, 2008 at 04:12:45PM +0530, Krishna Kumar wrote:
> From: Krishna Kumar <krkumar2@xxxxxxxxxx>
Thanks for the work, and apologies for the slow response.
>
> Patch summary:
> --------------
> Change the readahead caching on the server to a file handle caching model.
> Since file handles are unique, this patch removes all dependencies on the
> kernel readahead parameters/implementation and instead caches files based
> on file handles. This change allows the server to not have to open/close
> a file multiple times when the client reads it, and results in faster lookup
> times.
I think of open and lookup as fairly fast, so I'm surprised this makes a
great difference; do you have profile results or something to confirm
that this is in fact what made the difference?
> Also, readahead is automatically taken care of since the file is not
> closed while it is getting read (quickly) by the client.
>
>
> Read algo change:
> ------------------
> The new nfsd_read() is changed to:
> if file {
> Old code
> } else {
> Check if this FH is cached
> if fh && fh has cached file pointer:
> Get file pointer
> Update fields in fhp from cache
> call fh_verify
> else:
> Nothing in the cache, call nfsd_open as usual
>
> nfsd_vfs_read
>
> if fh {
> If this is a new fh entry:
> Save cached values
> Drop our reference to fh
> } else
> Close file
> }
When do items get removed from this cache?
>
>
> Performance:
> -------------
> This patch was tested with clients running 1, 4, 8, 16 --- 256 test processes,
> each doing reads of different files. Each test includes different I/O sizes.
> Many individual tests (16% of test cases) got throughput improvement in the
> 9 to 15% range. The full results are provided at the end of this post.
Could you provide details sufficient to reproduce this test if
necessary? (At least: what was the test code, how many clients were
used, what was the client and server hardware, and what filesystem was
the server exporting?)
--b.
>
> Please review. Any comments or improvement ideas are greatly appreciated.
>
> Signed-off-by: Krishna Kumar <krkumar2@xxxxxxxxxx>
> ---
>
> (#Test Processes on Client == #NFSD's on Server)
> --------------------------------------------------------------
> #Test Processes Org BW KB/s New BW KB/s %
> --------------------------------------------------------------
What's the second column?
> 4 256 48151.09 50328.70 4.52
> 4 4096 47700.05 49760.34 4.31
> 4 8192 47553.34 48509.00 2.00
> 4 16384 48764.87 51208.54 5.01
> 4 32768 49306.11 50141.59 1.69
> 4 65536 48681.46 49491.32 1.66
> 4 131072 48378.02 49971.95 3.29
>
> 8 256 38906.95 42444.95 9.09
> 8 4096 38141.46 42154.24 10.52
> 8 8192 37058.55 41241.78 11.28
> 8 16384 37446.56 40573.70 8.35
> 8 32768 36655.91 42159.85 15.01
> 8 65536 38776.11 40619.20 4.75
> 8 131072 38187.85 41119.04 7.67
>
> 16 256 36274.49 36143.00 -0.36
> 16 4096 34320.56 37664.35 9.74
> 16 8192 35489.65 34555.43 -2.63
> 16 16384 35647.32 36289.72 1.80
> 16 32768 37037.31 36874.33 -0.44
> 16 65536 36388.14 36991.56 1.65
> 16 131072 35729.34 37588.85 5.20
>
> 32 256 30838.89 32811.47 6.39
> 32 4096 31291.93 33439.83 6.86
> 32 8192 29885.57 33337.10 11.54
> 32 16384 30020.23 31795.97 5.91
> 32 32768 32805.03 33860.68 3.21
> 32 65536 31275.12 32997.34 5.50
> 32 131072 33391.85 34209.86 2.44
>
> 64 256 26729.46 28077.13 5.04
> 64 4096 25705.01 27339.37 6.35
> 64 8192 27757.06 27488.04 -0.96
> 64 16384 22927.44 23938.79 4.41
> 64 32768 26956.16 27848.52 3.31
> 64 65536 27419.59 29228.76 6.59
> 64 131072 27623.29 27651.99 .10
>
> 128 256 22463.63 22437.45 -.11
> 128 4096 22039.69 22554.03 2.33
> 128 8192 22218.42 24010.64 8.06
> 128 16384 15295.59 16745.28 9.47
> 128 32768 23319.54 23450.46 0.56
> 128 65536 22942.03 24169.26 5.34
> 128 131072 23845.27 23894.14 0.20
>
> 256 256 15659.17 16266.38 3.87
> 256 4096 15614.72 16362.25 4.78
> 256 8192 16950.24 17092.50 0.83
> 256 16384 9253.25 10274.28 11.03
> 256 32768 17872.89 17792.93 -.44
> 256 65536 18459.78 18641.68 0.98
> 256 131072 19408.01 20538.80 5.82
> --------------------------------------------------------------
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