On Fri 20-06-14 13:53:22, Matthew Wilcox wrote: > > I didn't see this with 3.14, but I'm not sure what's changed. > > When running generic/127, fsx ends up taking 30% CPU time with a kthread > taking 70% CPU time for hours. It might be making forward progress, > but if it is, it's incredibly slow. > > I can usually catch fsx waiting for the kthread: > > # ./check generic/127 > FSTYP -- ext4 > PLATFORM -- Linux/x86_64 walter 3.15.0 > MKFS_OPTIONS -- /dev/ram1 > MOUNT_OPTIONS -- -o acl,user_xattr /dev/ram1 /mnt/ram1 > > generic/127 19s ... > > $ sudo cat /proc/4795/stack > [<ffffffff8120bee9>] writeback_inodes_sb_nr+0xa9/0xe0 > [<ffffffff8120bfae>] try_to_writeback_inodes_sb_nr+0x5e/0x80 > [<ffffffff8120bff5>] try_to_writeback_inodes_sb+0x25/0x30 > [<ffffffffa01bae2a>] ext4_nonda_switch+0x8a/0x90 [ext4] > [<ffffffffa01c49a5>] ext4_page_mkwrite+0x265/0x440 [ext4] Hum, apparently you are running out of space on the test partition. And that is known to make ext4 extraordinarily slow... Honza > [<ffffffff811936ed>] do_page_mkwrite+0x3d/0x70 > [<ffffffff81195887>] do_wp_page+0x627/0x770 > [<ffffffff811981a1>] handle_mm_fault+0x781/0xf00 > [<ffffffff815a8996>] __do_page_fault+0x186/0x570 > [<ffffffff815a8da2>] do_page_fault+0x22/0x30 > [<ffffffff815a5038>] page_fault+0x28/0x30 > [<ffffffffffffffff>] 0xffffffffffffffff > > > My setup is a 1GB ram disk: > > modprobe brd rd_size=1048576 rd_nr=2 > > local.config: > > TEST_DEV=/dev/ram0 > TEST_DIR=/mnt/ram0 > SCRATCH_DEV=/dev/ram1 > SCRATCH_MNT=/mnt/ram1 > > > Hardware is an Intel(R) Core(TM) i7-4770 CPU @ 3.40GHz with 4GB RAM, > in case it matters. But I think what matters is that I'm running it on > a "tiny" 1GB filesystem, since this code is only invoked whenever the > number of dirty clusters is large relative to the number of free clusters. > > df shows: > /dev/ram1 999320 1284 929224 1% /mnt/ram1 > /dev/ram0 999320 646088 284420 70% /mnt/ram0 > > So it's not *unreasonably* full. > -- > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
