From: Paolo Bonzini <pbonzini@redhat.com>
To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Stephen Cameron <stephenmcameron@gmail.com>,
"James E.J. Bottomley" <JBottomley@parallels.com>,
Matthew Wilcox <willy@linux.intel.com>,
Tim Chen <tim.c.chen@linux.intel.com>,
linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] scsi_ram: a RAM-based SCSI driver
Date: Fri, 07 Dec 2012 23:24:34 +0100 [thread overview]
Message-ID: <50C26CA2.8080903@redhat.com> (raw)
In-Reply-To: <20121207112014.GA4466@otc-wbsnb-06>
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
prev parent reply other threads:[~2012-12-07 22:24 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-05 16:45 [PATCH] scsi_ram: a RAM-based SCSI driver Kirill A. Shutemov
2012-12-06 10:09 ` Paolo Bonzini
2012-12-07 11:20 ` Kirill A. Shutemov
2012-12-07 22:24 ` Paolo Bonzini [this message]
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