On Thu, Jul 25, 2013 at 09:17:01AM +0100, Steven Whitehouse wrote: > Hi, > > On Wed, 2013-07-24 at 12:47 +1000, Dave Chinner wrote: > > On Tue, Jul 23, 2013 at 02:58:58PM -0700, Jeremy Allison wrote: > > > Having said that the OEMs that are using it does > > > find it improves write speeds by a large amount (10% > > > or more), so it's showing there is room for improvement > > > here if the correct code can be created for recvfile. > > > > 10% is not very large gain given the complexity it adds, and I > > question that the gain actually comes from moving the memcpy() into > > the kernel. If this recvfile code enabled zero-copy behaviour into > > the page cache, then it would be worth pursuing. But it doesn't, and > > so IMO the complexity is not worth the gain right now. > > > > Indeed, I suspect the 10% gain will be from the multi-page write > > behaviour that was hacked into the code. I wrote a multi-page > > write prototype ~3 years ago that showed write(2) performance gains > > of roughly 10% on low CPU power machines running XFS. ... > > I should probably pick this up again and push it forwards. FWIW, > > I've attached the first multipage-write infrastructure patch from > > the above branch to show how this sort of operation needs to be done > > from a filesystem and page-cache perspective to avoid locking > > problems have sane error handling. > > > > I beleive the version that Christoph implemented for a couple of > > OEMs around that time de-multiplexed the ->iomap method.... > > I have Christoph's version here and between other tasks, I'm working on > figuring out how it all works and writing GFS2 support for it. I'd more > or less got that complete for your version, but there are a number of > differences with Christoph's code and it is taking me a while to ensure > that I've not missed any corner cases and figuring out how to fit some > of GFS2's odd write modes into the framework, Can you send me Christoph's version so I can have a look at the differences? I'm pretty sure there isn't anything architecturally different, but I've never seen it so I don't know exactly how it differs... Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
