Messages in this thread | | | Subject | Re: Bad SSD performance with recent kernels | From | Eric Dumazet <> | Date | Sun, 29 Jan 2012 14:13:51 +0100 |
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Le dimanche 29 janvier 2012 à 19:16 +0800, Wu Fengguang a écrit :
> Note that as long as buffered read(2) is used, it makes almost no > difference (well, at least for now) to do "dd bs=128k" or "dd bs=2MB": > the 128kb readahead size will be used underneath to submit read IO. >
Hmm...
# echo 3 >/proc/sys/vm/drop_caches ;dd if=/dev/sda of=/dev/null bs=128k count=32768 32768+0 enregistrements lus 32768+0 enregistrements écrits 4294967296 octets (4,3 GB) copiés, 20,7718 s, 207 MB/s
# echo 3 >/proc/sys/vm/drop_caches ;dd if=/dev/sda of=/dev/null bs=2M count=2048 2048+0 enregistrements lus 2048+0 enregistrements écrits 4294967296 octets (4,3 GB) copiés, 27,7824 s, 155 MB/s
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