From: Krishna Kumar <krkumar2@xxxxxxxxxx>
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. 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
}
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.
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 %
--------------------------------------------------------------
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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