On Wed 19-06-19 19:34:00, Zhangjs Jinshui wrote: > You can blktrace > > 8,80 31 11 0.296373038 2885275 Q RA 8279571464 + 8 [xxxx] > 8,80 31 12 0.296374017 2885275 G RA 8279571464 + 8 [xxxx] > 8,80 31 13 0.296375468 2885275 I RA 8279571464 + 8 [xxxx] > 8,80 31 14 0.296382099 3886 D RA 8279571464 + 8 [kworker/31:1H] > 8,80 31 15 0.296391907 2885275 Q RA 8279571472 + 8 [xxxx] > 8,80 31 16 0.296392275 2885275 G RA 8279571472 + 8 [xxxx] > 8,80 31 17 0.296393305 2885275 I RA 8279571472 + 8 [xxxx] > 8,80 31 18 0.296395844 3886 D RA 8279571472 + 8 [kworker/31:1H] > 8,80 31 19 0.296399685 2885275 Q RA 8279571480 + 8 [xxxx] > 8,80 31 20 0.296400025 2885275 G RA 8279571480 + 8 [xxxx] > 8,80 31 21 0.296401232 2885275 I RA 8279571480 + 8 [xxxx] > 8,80 31 22 0.296403422 3886 D RA 8279571480 + 8 [kworker/31:1H] > 8,80 31 23 0.296407375 2885275 Q RA 8279571488 + 8 [xxxx] > 8,80 31 24 0.296407721 2885275 G RA 8279571488 + 8 [xxxx] > 8,80 31 25 0.296408904 2885275 I RA 8279571488 + 8 [xxxx] > 8,80 31 26 0.296411127 3886 D RA 8279571488 + 8 [kworker/31:1H] > 8,80 31 27 0.296414779 2885275 Q RA 8279571496 + 8 [xxxx] > 8,80 31 28 0.296415119 2885275 G RA 8279571496 + 8 [xxxx] > 8,80 31 29 0.296415744 2885275 I RA 8279571496 + 8 [xxxx] > 8,80 31 30 0.296417779 3886 D RA 8279571496 + 8 [kworker/31:1H] > > these RA io were caused by ext4_inode_readahead_blks, there are all not merged becourse of the unplugged state. > the backtrace shows below, was traced by systemtap ioblock.request filtered by "opf & 1 << 19" > > 0xffffffff8136fb20 : generic_make_request+0x0/0x2f0 [kernel] > 0xffffffff8136fe7e : submit_bio+0x6e/0x130 [kernel] > 0xffffffff812971e6 : submit_bh_wbc+0x156/0x190 [kernel] > 0xffffffff81297bca : ll_rw_block+0x6a/0xb0 [kernel] > 0xffffffff81297cc0 : __breadahead+0x40/0x70 [kernel] > 0xffffffffa0392c9a : __ext4_get_inode_loc+0x37a/0x3d0 [ext4] > 0xffffffffa0396a6c : ext4_iget+0x8c/0xc00 [ext4] > 0xffffffffa03ad98a : ext4_lookup+0xca/0x1d0 [ext4] > 0xffffffff8126b814 : path_openat+0xcb4/0x1250 [kernel] > 0xffffffff8126dc41 : do_filp_open+0x91/0x100 [kernel] > 0xffffffff8125ad86 : do_sys_open+0x126/0x210 [kernel] > 0xffffffff81003864 : do_syscall_64+0x74/0x1a0 [kernel] > 0xffffffff81800081 : entry_SYSCALL_64_after_hwframe+0x3d/0xa2 [kernel] > > I have patched it on online servers, It can improved the performance. Ah, OK, directory lookup code... Makes sense. Thanks for sharing! Honza > > > 在 2019年6月19日，19:08，Jan Kara <jack@xxxxxxx> 写道： > > > > On Mon 17-06-19 23:57:12, jinshui zhang wrote: > >> From: zhangjs <zachary@xxxxxxxxxxxxxxxx <mailto:zachary@xxxxxxxxxxxxxxxx>> > >> > >> If the task is unplugged when called, the inode_readahead_blks may not be merged, > >> these will cause small pieces of io, It should be plugged. > >> > >> Signed-off-by: zhangjs <zachary@xxxxxxxxxxxxxxxx <mailto:zachary@xxxxxxxxxxxxxxxx>> > > > > Out of curiosity, on which path do you see __ext4_get_inode_loc() being > > called without IO already plugged? > > > > Otherwise the patch looks good to me. You can add: > > > > Reviewed-by: Jan Kara <jack@xxxxxxx <mailto:jack@xxxxxxx>> > > > > Honza > > > >> --- > >> fs/ext4/inode.c | 6 ++++++ > >> 1 file changed, 6 insertions(+) > >> > >> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c > >> index c7f77c6..8fe046b 100644 > >> --- a/fs/ext4/inode.c > >> +++ b/fs/ext4/inode.c > >> @@ -4570,6 +4570,7 @@ static int __ext4_get_inode_loc(struct inode *inode, > >> struct buffer_head *bh; > >> struct super_block *sb = inode->i_sb; > >> ext4_fsblk_t block; > >> + struct blk_plug plug; > >> int inodes_per_block, inode_offset; > >> > >> iloc->bh = NULL; > >> @@ -4654,6 +4655,8 @@ static int __ext4_get_inode_loc(struct inode *inode, > >> } > >> > >> make_io: > >> + blk_start_plug(&plug); > >> + > >> /* > >> * If we need to do any I/O, try to pre-readahead extra > >> * blocks from the inode table. > >> @@ -4688,6 +4691,9 @@ static int __ext4_get_inode_loc(struct inode *inode, > >> get_bh(bh); > >> bh->b_end_io = end_buffer_read_sync; > >> submit_bh(REQ_OP_READ, REQ_META | REQ_PRIO, bh); > >> + > >> + blk_finish_plug(&plug); > >> + > >> wait_on_buffer(bh); > >> if (!buffer_uptodate(bh)) { > >> EXT4_ERROR_INODE_BLOCK(inode, block, > >> -- > >> 1.8.3.1 > >> > > -- > > Jan Kara <jack@xxxxxxxx <mailto:jack@xxxxxxxx>> > > SUSE Labs, CR > -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
