Re: [PATCH] readahead: initial method - expected read size - fix fastcall

[Fengguang Wu <wfg@mail.ustc.edu.cn>]

It's interesting that copying of sparse file is more efficient with small
readahead size :) I get the same conclusion, though with smaller differences:

SUMMARY
              user       sys       cpu         total
ARA, 1M       0.15       6.28      82.80       7.73
ARA, 128k     0.14       6.09      85.60       7.26
STOCK, 128k   0.15       6.05      85.60       7.22

TEST CASE

wfg ~% ll work/sparse
-rw-r--r-- 1 wfg wfg 1.6G 2006-05-21 15:11 work/sparse
wfg ~% free
             total       used       free     shared    buffers     cached
Mem:           501        496          5          0          5        191
-/+ buffers/cache:        300        201
Swap:          127          0        127

wfg ~% time cp work/sparse /dev/null

ARA, 1M
cp work/sparse /dev/null  0.15s user 6.35s system 80% cpu 8.125 total
cp work/sparse /dev/null  0.14s user 6.28s system 84% cpu 7.556 total
cp work/sparse /dev/null  0.14s user 6.25s system 82% cpu 7.744 total
cp work/sparse /dev/null  0.15s user 6.23s system 85% cpu 7.495 total
cp work/sparse /dev/null  0.16s user 6.30s system 83% cpu 7.719 total

ARA, 128k
cp work/sparse /dev/null  0.15s user 6.07s system 86% cpu 7.224 total
cp work/sparse /dev/null  0.15s user 6.05s system 84% cpu 7.334 total
cp work/sparse /dev/null  0.14s user 6.18s system 86% cpu 7.328 total
cp work/sparse /dev/null  0.13s user 6.11s system 86% cpu 7.217 total
cp work/sparse /dev/null  0.14s user 6.06s system 86% cpu 7.179 total

STOCK, 128k
cp work/sparse /dev/null  0.16s user 6.01s system 86% cpu 7.162 total
cp work/sparse /dev/null  0.14s user 6.10s system 86% cpu 7.222 total
cp work/sparse /dev/null  0.14s user 6.04s system 86% cpu 7.186 total
cp work/sparse /dev/null  0.15s user 6.02s system 85% cpu 7.210 total
cp work/sparse /dev/null  0.14s user 6.09s system 85% cpu 7.320 total

Wu