On 07/29/2011 06:25 PM, Sasha Levin wrote:
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
Agree. vhost-net works around the lack of async zero copy networking interface. Block I/O on the other hand does have such an interface, and in addition transaction rates are usually lower. All we're saving is the syscall overhead.
-- error compiling committee.c: too many arguments to function -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
