On Thu, Dec 06, 2012 at 11:09:07AM +0100, Paolo Bonzini wrote: > Il 05/12/2012 17:45, Kirill A. Shutemov ha scritto: > > From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> > > > > This driver is intended to run as fast as possible, hence the options to > > discard writes and reads. It's designed to let us find latency issues > > elsewhere in the storage stack (eg filesystem, block layer, scsi layer). > > > > There are a few different options, controlled through module parameters. > > The sector size and disc capacity are load-time parameters, but the > > parameters affecting performance are tweakable at runtime. > > > > By default, it'll allocate half a gigabyte of RAM to use as a ramdisc; > > you can change this with the `capacity' module parameter. > > Is this that much faster than scsi-debug? The discarding options surely > can be added there. scsi_ram is about 9% faster (without fake_rw/throw_away_*) on my machine: fio job file (slightly modified ssd-test): [global] bs=4k ioengine=libaio iodepth=4 size=10g direct=1 runtime=60 filename=/dev/sdb [seq-read] rw=read stonewall [rand-read] rw=randread stonewall [seq-write] rw=write stonewall [rand-write] rw=randwrite stonewall ---------------------- scsi_ram capacity=41943040: Run status group 0 (all jobs): READ: io=6975.2MB, aggrb=119040KB/s, minb=119040KB/s, maxb=119040KB/s, mint=60001msec, maxt=60001msec Run status group 1 (all jobs): READ: io=7006.8MB, aggrb=119579KB/s, minb=119579KB/s, maxb=119579KB/s, mint=60001msec, maxt=60001msec Run status group 2 (all jobs): WRITE: io=7009.9MB, aggrb=119632KB/s, minb=119632KB/s, maxb=119632KB/s, mint=60001msec, maxt=60001msec Run status group 3 (all jobs): WRITE: io=6919.8MB, aggrb=118094KB/s, minb=118094KB/s, maxb=118094KB/s, mint=60001msec, maxt=60001msec Disk stats (read/write): sdb: ios=3579612/3559798, merge=0/0, ticks=128180/125565, in_queue=240098, util=77.79% ---------------------- scsi_debug dev_size_mb=10240 delay=0: Run status group 0 (all jobs): READ: io=6393.2MB, aggrb=109110KB/s, minb=109110KB/s, maxb=109110KB/s, mint=60000msec, maxt=60000msec Run status group 1 (all jobs): READ: io=6327.6MB, aggrb=107988KB/s, minb=107988KB/s, maxb=107988KB/s, mint=60001msec, maxt=60001msec Run status group 2 (all jobs): WRITE: io=6473.3MB, aggrb=110474KB/s, minb=110474KB/s, maxb=110474KB/s, mint=60001msec, maxt=60001msec Run status group 3 (all jobs): WRITE: io=6330.5MB, aggrb=108037KB/s, minb=108037KB/s, maxb=108037KB/s, mint=60001msec, maxt=60001msec Disk stats (read/write): sdb: ios=3256653/3272376, merge=0/0, ticks=54502/54150, in_queue=101165, util=42.09% -- Kirill A. Shutemov
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