Re: [PATCH 5/5] virtio-blk: implement ->make_request

[Jens Axboe]

On Wed, Oct 05 2011, Christoph Hellwig wrote:
> Add an alternate I/O path that implements ->make_request for virtio-blk.
> This is required for high IOPs devices which get slowed down to 1/5th of
> the native speed by all the locking, memory allocation and other overhead
> in the request based I/O path.

We definitely have some performance fruit hanging rather low in that
path, but a factor 5 performance difference sounds insanely excessive. I
haven't looked at virtio_blk in detail, but I've done 500K+ IOPS on
request based drivers before (yes, on real hardware). So it could be
that virtio_blk is just doing things rather suboptimally in some places,
and that it would be possible to claim most of that speedup there too.

-- 
Jens Axboe

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