On Tue, May 09, 2017 at 03:49:13PM -0700, Liu Bo wrote: > On Fri, May 05, 2017 at 04:24:47PM +0200, David Sterba wrote: > > On Mon, Apr 17, 2017 at 06:16:21PM -0700, Liu Bo wrote: > > > This attempts to use bio_clone_fast() in the places where we clone bio, > > > such as when bio got cloned for multiple disks and when bio got split > > > during dio submit. > > > > > > One benefit is to simplify dio submit to avoid calling bio_add_page one by > > > one. > > > > > > Another benefit is that comparing to bio_clone_bioset, bio_clone_fast is > > > faster because of copying the vector pointer directly, and bio_clone_fast > > > doesn't modify bi_vcnt, so the extra work is to fix up bi_vcnt usage we > > > currently have to use bi_iter to iterate bvec. > > > > > > Liu Bo (6): > > > Btrfs: use bio_clone_fast to clone our bio > > > > Please extend the changelog of this patch, use the text in the cover > > letter. > > > > OK. > > > > Btrfs: use bio_clone_bioset_partial to simplify DIO submit > > > > This patch is too big, can you split it to smaller chunks? I was not > > able to review it, it seems to touch several things at once, it's hard > > to keep the context. > > > > Oh I see, the diff does look scary but the changes are in fact not > intrusive, I'll try to do something. > > > > Btrfs: change how we iterate bios in endio > > > Btrfs: record error if one block has failed to retry > > > Btrfs: change check-integrity to use bvec_iter > > > Btrfs: unify naming of btrfs_io_bio > > > > The rest looks ok. > > > > Have you done perofrmance tests? Not that it's necessary, but would be > > interesting to see the effects. The effects of simplified code are > > likely unmeasurable, but the _fast version skips some mempool exercises > > so this could lead to improvements under memory pressure. And these is > > hardly deterministic conditions, could be hard. I'me expecting some > > latency improvemtnest. > > I haven't done the perf. test since it is a RFC that I basically hope > to check whether the idea makes sense. > > And yes, using bio_clone_fas could save us some memory which is > allocated for bio->bi_io_vec if (nr_iovecs > inline_vecs).
A quick test[1] showed a slightly better result, I ran the test 5 times each round and took the average value, vanilla 4.11-rc5: 15.39s patched 4.11-rc5: 14.12s [1] M=/mnt/btrfs D1=/dev/pmem0p1 D2=/dev/pmem0p2 umount $M mkfs.btrfs -f $D1 $D2 >/dev/null || exit mount $D1 $M -onodatasum || exit xfs_io -f -c "falloc 0 2G" $M/foo time xfs_io -d -c "pwrite -b 128K 0 2G" $M/foo Thanks, -liubo -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
