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由 Akinobu Mita 提交于
Sequential read from a block device is expected to be equal or faster than from the file on a filesystem. But it is not correct due to the lack of effective readpages() in the address space operations for block device. This implements readpages() operation for block device by using mpage_readpages() which can create multipage BIOs instead of BIOs for each page and reduce system CPU time consumption. Install 1GB of RAM disk storage: # modprobe scsi_debug dev_size_mb=1024 delay=0 Sequential read from file on a filesystem: # mkfs.ext4 /dev/$DEV # mount /dev/$DEV /mnt # fio --name=t --size=512m --rw=read --filename=/mnt/file ... read : io=524288KB, bw=2133.4MB/s, iops=546133, runt= 240msec Sequential read from a block device: # fio --name=t --size=512m --rw=read --filename=/dev/$DEV ... (Without this commit) read : io=524288KB, bw=1700.2MB/s, iops=435455, runt= 301msec (With this commit) read : io=524288KB, bw=2160.4MB/s, iops=553046, runt= 237msec Signed-off-by: NAkinobu Mita <akinobu.mita@gmail.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Jeff Moyer <jmoyer@redhat.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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