On 05/31, Barry Song via Linux-f2fs-devel wrote: > On Sun, May 31, 2026 at 8:12 AM Jaegeuk Kim <[email protected]> wrote: > > > > On 05/28, Christoph Hellwig wrote: > > > On Wed, May 27, 2026 at 03:59:35PM +0000, Jaegeuk Kim wrote: > > > > F2FS merges bios before submit_bio, regardless of small or large folios, > > > > since the block addresses are consecutive. So, I think IO subsystem was > > > > working in full speed. > > > > > > As does every other remotely modern file system. But that merging is > > > surprisingly expensive, which is why using folios gets really major > > > performance improvements. > > > > > > For one doing these checks to merge touch quite a few cache lines. > > > Second, devices are often a lot more efficient if they see fewer SGL > > > entries. I.e. having a 1MB bio a single SGL tends to work better than > > > having 256 of them. > > > The same is true in the kernel code itself, both in the submission path > > > (dma mapping and co), and even more so in the page cache handling > > > both before submitting and in the completion path. > > > > > > See Bart's patch about how long the walk of the bio_vecs in the f2fs > > > completion path can take. We had similar issues in XFS even in the > > > workqueue completion path due to lack of rescheduling, and these simply > > > go away when you do the folio manipulation in larger chunks (LAZY_PREEMPT > > > would avoid the need to explicit rescheduling these days, but that just > > > papers over the symptoms in this case). > > > > > > > I see. That's also super helpful. Let me kick off the large folio support > > asap. > > Thanks. > > Hi Jaegeuk,
Hi Barry, > > Nanzhe has put significant effort into this work at Xiaomi over > the past several months. Large folios can now be supported on > non-immutable files. > > He has conducted extensive testing on the Pixel 6 and fixed a > number of hangs discovered during development. He is still > benchmarking performance, but the implementation appears to be > reasonably stable at this point. We can run Android Monkey for > many hours without observing any hangs. > > If you would like to see an RFC, I can ask Nanzhe to send one > as soon as possible after some cleanup and polishing. Yeah, I was about to reach out to you. Let's do some discussion offline. Thanks, > > Best regards, > Barry > > > _______________________________________________ > Linux-f2fs-devel mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel _______________________________________________ Linux-f2fs-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
