Messages in this thread |  | | | Subject | Re: [RFC PATCH]vhost-blk: In-kernel accelerator for virtio block device | | From | Sasha Levin <> | | Date | Fri, 29 Jul 2011 18:25:04 +0300 |
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On Fri, 2011-07-29 at 20:01 +0800, Liu Yuan wrote: > Looking at this long list,most are function pointers that can not be > inlined, and the internal data structures used by these functions are > dozons. Leave aside code complexity, this long code path would really > need retrofit. As Christoph simply put, this kind of mess is inherent > all over the qemu code. So I am afraid, the 'retrofit' would end up to > be a re-write the entire (sub)system. I have to admit that, I am > inclined to the MST's vhost approach, that write a new subsystem other > than tedious profiling and fixing, that would possibly goes as far as > actually re-writing it.
I don't think the fix for problematic userspace is to write more kernel code.
vhost-net improved throughput and latency by several factors, allowing to achieve much more than was possible at userspace alone.
With vhost-blk we see an improvement of ~15% - which I assume by your and Christoph's comments can be mostly attributed to QEMU. Merging a module which won't improve performance dramatically compared to what is possible to achieve in userspace (even if it would require a code rewrite) sounds a bit wrong to me.
--
Sasha.
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