Messages in this thread | | | Date | Sat, 1 Nov 2003 18:22:16 +0100 | From | Voluspa <> | Subject | Re: READAHEAD |
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On 2003-11-01 9:15:28 Age Huisman wrote: >Andrew Morton wrote: >> Andrew Morton <akpm@osdl.org> wrote: >> >>>Please, just use time, cat, dd, etc. >>> >>> mount /dev/xxx /mnt/yyy >>> dd if=/dev/zero of=/mnt/yyy/x bs=1M count=1024 >>> umount /dev/xxx >>> mount /dev/xxx /mnt/yyy >>> time cat /mnt/yyy/x > /dev/null [...] >Here are the new test results. [...] >I think you were right :-)
I see an improvement with 512 instead of the default 256, but no further speedups with 1024 or 2048 - no point in trying 4096:
readahead = 256 (on) real 0m39.494s user 0m0.346s sys 0m5.436s Timing buffered disk reads: 64 MB in 2.80 seconds = 22.84 MB/sec
readahead = 512 (on) real 0m34.418s user 0m0.302s sys 0m5.304s Timing buffered disk reads: 64 MB in 2.16 seconds = 29.63 MB/sec
And for the nostalgic people out there, here's what "hdparm /dev/hdX" has in its readahead slot under 2.5.X:
2.5.5-pre1 readahead = 8 (on)
2.5.5-pre1-final (AKA 2.5.5) to 2.5.8-pre2 BLKRAGET failed: Input/output error
2.5.8-pre3 to 2.5.9 don't compile.
2.5.10 readahead = 0 (off)
2.5.11 failed to boot and damaged the filesystem.
2.5.12 and onwards readahead = 256 (on)
Mvh Mats Johannesson - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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