Mauro Triulzi wrote this message on Mon, Sep 27, 2004 at 02:20 +0200: > ii) Now I tried a fair raw throughput comparison between Linux and > FreeBSD. This time I read always the same whole (Linux) partition > (~4GB) so that the results should be comparable. I always used native > dd (FreeBSD and Linux). A measure with Linux dd under emulation > in FreeBSD gave yet the same result: > > dd if=/dev/ad0s9 bs=nnn of=/dev/null > FreeBSD: > nnn=4k: 4301789184 bytes transferred in 170.031898 secs (25299895 > bytes/sec) > nnn=8k: 4301789184 bytes transferred in 114.446100 secs (37587905 > bytes/sec) > nnn=16k: 4301789184 bytes transferred in 87.794076 secs (48998627 > bytes/sec) > nnn=64k: 4301789184 bytes transferred in 89.515195 secs (48056525 > bytes/sec) > nnn=512k: 4301789184 bytes transferred in 90.357666 secs (47608458 > bytes/sec) > (no significant changes before or after reinit) > > Linux: > nnn=4k: 4301789184 bytes transferred in 93 secs (~46 Mbytes/sec) > nnn=8k: 4301789184 bytes transferred in 86 secs (~50 Mbytes/sec) > nnn=16k: 4301789184 bytes transferred in 90 secs (~48 Mbytes/sec) > nnn=64k: 4301789184 bytes transferred in 95 secs (~45 Mbytes/sec) > nnn=512k: 4301789184 bytes transferred in 92 secs (~47 Mbytes/sec) > > I notice, that the rates are very similar if bs >= 16k. Under FreeBSD > the raw throughput rate depends on the block size. Read rate under Linux > is independent of the block size. Is there a special reason for that? Last I heard Linux did not have a raw device.. this means that it will always be cached, and will do various read-ahead optimizations, while FreeBSD does not have a buffered/cooked device anymore.. w/o the cooked device FreeBSD has to suffer the latency of the command to the drive... -- John-Mark Gurney Voice: +1 415 225 5579 "All that I will do, has been done, All that I have, has not."Received on Mon Sep 27 2004 - 01:15:33 UTC
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