Messages in this thread |  | | | Date | Mon, 13 Sep 2010 17:21:38 +0200 | | From | Johannes Stezenbach <> | | Subject | Re: block cache replacement strategy? |
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On Fri, Sep 10, 2010 at 06:02:48PM +0200, Johannes Stezenbach wrote: > > Linear read heuristic might be a good guess, but it would > be nice to hear a comment from a vm/fs expert which > confirms this works as intended.
Apparently I'm unworthy to get a response from someone knowledgable :-(
Anyway I found lmdd (from lmbench) can do random reads, and indeed causes the data to enter the block (page?) cache, replacing the previous data.
Johannes
zzz:~# echo 3 >/proc/sys/vm/drop_caches
zzz:~# ./lmdd if=~js/qemu/test.img bs=1M count=1000 1000.0000 MB in 17.7554 secs, 56.3210 MB/sec zzz:~# ./lmdd if=~js/qemu/test.img bs=1M count=1000 1000.0000 MB in 0.9112 secs, 1097.4178 MB/sec zzz:~# ./lmdd if=~js/qemu/test2.img bs=1M count=1000 rand=1G norepeat= norepeat on 238035072 norepeat on 724579648 1000.0000 MB in 21.4419 secs, 46.6376 MB/sec zzz:~# ./lmdd if=~js/qemu/test2.img bs=1M count=1000 rand=1G norepeat= norepeat on 238035072 norepeat on 724579648 1000.0000 MB in 14.3859 secs, 69.5125 MB/sec zzz:~# ./lmdd if=~js/qemu/test2.img bs=1M count=1000 rand=1G norepeat= norepeat on 238035072 norepeat on 724579648 1000.0000 MB in 0.8764 secs, 1141.0810 MB/sec
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