On Tue, Jan 6, 2015 at 3:47 AM, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > On Mon, 5 Jan 2015 10:41:43 -0800 Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote: > >> On Wed, Dec 10, 2014 at 09:12:11AM -0500, Matthew Wilcox wrote: >> > On Wed, Dec 10, 2014 at 06:03:47AM -0800, Christoph Hellwig wrote: >> > > What is the status of this patch set? >> > >> > I have no outstanding bug reports against it. Linus told me that he >> > wants to see it come through Andrew's tree. I have an email two weeks >> > ago from Andrew saying that it's on his list. I would love to see it >> > merged since it's almost a year old at this point. >> >> And since then another month and aother merge window has passed. Is >> there any way to speed up merging big patch sets like this one? > > I took a look at dax last time and found it to be unreviewable due to > lack of design description, objectives and code comments. Hopefully > that's been addressed - I should get back to it fairly soon as I chew > through merge window and holiday backlog. > >> Another one is non-blocking read one that has real life use on one >> of the biggest server side webapp frameworks but doesn't seem to make >> progress, which is a bit frustrating. > > I took a look at pread2() as well and I have two main issues: > > - The patchset includes a pwrite2() syscall which has nothing to do > with nonblocking reads and which was poorly described and had little > justification for inclusion. > > - We've talked for years about implementing this via fincore+pread > and at least two fincore implementations are floating about. Now > along comes pread2() which does it all in one hit. > > Which approach is best? I expect fincore+pread is simpler, more > flexible and more maintainable. But pread2() will have lower CPU > consumption and lower average-case latency. > > But how *much* better is pread2()? I expect the difference will be > minor because these operations are associated with a great big > cache-stomping memcpy. If the pread2() advantage is "insignificant > for real world workloads" then perhaps it isn't the best way to go. > > I just don't know, and diligence requires that we answer the > question. But all I've seen in response to these questions is > handwaving. It would be a shame to make a mistake because nobody > found the time to perform the investigation. > > Also, integration of pread2() into xfstests is (or was) happening and > the results of that aren't yet known. > Andrew I got busier with my other job related things between the Thanksgiving & Christmas then anticipated. However, I have updated and taken apart the patchset into two pieces (preadv2 and pwritev2). That should make evaluating the two separately easier. With the help of Volker I hacked up preadv2 support into samba and I hopefully have some numbers from it soon. Finally, I'm putting together a test case for the typical webapp middle-tier service (epoll + threadpool for diskio). Haven't stopped, just progressing on that slower due to external factors. P.S: Sorry for re-send. On the road and was using gmail to respond with... it randomly forgets plain-text only settings. -- Milosz Tanski CTO 16 East 34th Street, 15th floor New York, NY 10016 p: 646-253-9055 e: milosz@xxxxxxxxx -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>