Re: [PATCH] scsi_ram: a RAM-based SCSI driver

[Paolo Bonzini]

Il 07/12/2012 12:20, Kirill A. Shutemov ha scritto:
>> > 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:

There are two main differences in the data path:

- scsi_debug uses locking.  Shouldn't be the culprit because otherwise
read and write would have different speed, but it's easy to add it to
scsi_ram and check.

- scsi_debug uses scsi_sg_copy_to_buffer, i.e. sg_miter_start/next/stop
in kernel/scatterlist.c.  Again, it should be easy to port the scsi_ram
code to scsi_debug or vice versa and verify if this is the culprit.

Having a completely different driver seems useless to me...

Paolo
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