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Dave Chinner d353d7587d writeback: plug writeback at a high level 
Doing writeback on lots of little files causes terrible IOPS storms
because of the per-mapping writeback plugging we do. This
essentially causes imeediate dispatch of IO for each mapping,
regardless of the context in which writeback is occurring.

IOWs, running a concurrent write-lots-of-small 4k files using fsmark
on XFS results in a huge number of IOPS being issued for data
writes.  Metadata writes are sorted and plugged at a high level by
XFS, so aggregate nicely into large IOs. However, data writeback IOs
are dispatched in individual 4k IOs, even when the blocks of two
consecutively written files are adjacent.

Test VM: 8p, 8GB RAM, 4xSSD in RAID0, 100TB sparse XFS filesystem,
metadata CRCs enabled.

Kernel: 3.10-rc5 + xfsdev + my 3.11 xfs queue (~70 patches)

Test:

$ ./fs_mark  -D  10000  -S0  -n  10000  -s  4096  -L  120  -d
/mnt/scratch/0  -d  /mnt/scratch/1  -d  /mnt/scratch/2  -d
/mnt/scratch/3  -d  /mnt/scratch/4  -d  /mnt/scratch/5  -d
/mnt/scratch/6  -d  /mnt/scratch/7

Result:

		wall	sys	create rate	Physical write IO
		time	CPU	(avg files/s)	 IOPS	Bandwidth
		-----	-----	------------	------	---------
unpatched	6m56s	15m47s	24,000+/-500	26,000	130MB/s
patched		5m06s	13m28s	32,800+/-600	 1,500	180MB/s
improvement	-26.44%	-14.68%	  +36.67%	-94.23%	+38.46%

If I use zero length files, this workload at about 500 IOPS, so
plugging drops the data IOs from roughly 25,500/s to 1000/s.
3 lines of code, 35% better throughput for 15% less CPU.

The benefits of plugging at this layer are likely to be higher for
spinning media as the IO patterns for this workload are going make a
much bigger difference on high IO latency devices.....

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Josef Bacik <jbacik@fb.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Tested-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
 		2015-08-17 18:39:45 -04:00
..
9p 9p: don't leave a half-initialized inode sitting around 2015-07-12 11:22:05 -04:00
adfs fs/adfs: remove unneeded cast 2015-06-30 19:44:57 -07:00
affs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2015-07-04 19:36:06 -07:00
afs net: Add a struct net parameter to sock_create_kern 2015-05-11 10:50:17 -04:00
autofs4 make simple_positive() public 2015-06-23 18:02:01 -04:00
befs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2015-07-04 19:36:06 -07:00
bfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2015-04-26 17:22:07 -07:00
btrfs Merge branch 'for-linus-4.2' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs 2015-08-09 05:56:31 +03:00
cachefiles Merge branch 'fscache-fixes' into for-next 2015-06-23 18:01:30 -04:00
ceph ceph: always re-send cap flushes when MDS recovers 2015-07-31 11:38:53 +03:00
cifs cifs: Unset CIFS_MOUNT_POSIX_PATHS flag when following dfs mounts 2015-06-29 14:50:22 -05:00
coda fs: cleanup slight list_entry abuse 2015-06-23 18:01:59 -04:00
configfs configfs: fix kernel infoleak through user-controlled format string 2015-07-17 16:39:53 -07:00
cramfs fs/cramfs/inode.c: use linux/uaccess.h 2014-08-08 15:57:25 -07:00
debugfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2015-07-04 19:36:06 -07:00
devpts devpts: if initialization failed, don't crash when opening /dev/ptmx 2015-06-30 19:44:58 -07:00
dlm net: Add a struct net parameter to sock_create_kern 2015-05-11 10:50:17 -04:00
ecryptfs ioctl_compat: handle FITRIM 2015-07-09 11:42:21 -07:00
efivarfs Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2015-05-06 10:57:37 -07:00
efs fs/efs: femove unneeded cast 2015-06-25 17:00:42 -07:00
exofs pagemap.h: move dir_pages() over there 2015-06-23 18:02:00 -04:00
exportfs VFS: (Scripted) Convert S_ISLNK/DIR/REG(dentry->d_inode) to d_is_*(dentry) 2015-02-22 11:38:41 -05:00
ext2 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2015-07-04 19:36:06 -07:00
ext3 Merge branch 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs 2015-06-24 20:07:10 -07:00
ext4 ioctl_compat: handle FITRIM 2015-07-09 11:42:21 -07:00
f2fs f2fs: call set_page_dirty to attach i_wb for cgroup 2015-07-25 08:54:26 -07:00
fat writeback: separate out include/linux/backing-dev-defs.h 2015-06-02 08:33:34 -06:00
freevxfs pagemap.h: move dir_pages() over there 2015-06-23 18:02:00 -04:00
fscache FS-Cache: Retain the netfs context in the retrieval op earlier 2015-04-02 14:28:53 +01:00
fuse Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2015-07-04 19:36:06 -07:00
gfs2 GFS2: merge window 2015-06-27 09:47:46 -07:00
hfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2015-07-04 19:36:06 -07:00
hfsplus Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2015-07-04 19:36:06 -07:00
hostfs Merge branch 'for-linus-1' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2015-06-22 12:51:21 -07:00
hpfs hpfs: hpfs_error: Remove static buffer, use vsprintf extension %pV instead 2015-07-09 13:35:31 -07:00
hugetlbfs ipc: use private shmem or hugetlbfs inodes for shm segments. 2015-08-07 04:39:41 +03:00
isofs VFS: normal filesystems (and lustre): d_inode() annotations 2015-04-15 15:06:57 -04:00
jbd jbd: Deletion of an unnecessary check before the function call "iput" 2014-11-18 10:15:29 +01:00
jbd2 Revert "jbd2: speedup jbd2_journal_dirty_metadata()" 2015-06-27 09:41:50 -07:00
jffs2 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2015-07-04 19:36:06 -07:00
jfs A couple trivial fixes and an error path fix 2015-07-16 16:28:28 -07:00
kernfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2015-07-03 15:20:57 -07:00
lockd nfsd: eliminate NFSD_DEBUG 2015-04-21 16:16:02 -04:00
logfs logfs: fix a pagecache leak for symlinks 2015-05-10 22:18:28 -04:00
minix Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2015-07-04 19:36:06 -07:00
ncpfs ncpfs: successful rename() should invalidate caches for parents 2015-06-14 11:31:39 -04:00
nfs NFS client bugfixes for Linux 4.2 2015-07-28 09:37:44 -07:00
nfs_common lockd: move lockd's grace period handling into its own module 2014-09-17 16:33:11 -04:00
nfsd nfsd: do nfs4_check_fh in nfs4_check_file instead of nfs4_check_olstateid 2015-07-31 16:30:26 -04:00
nilfs2 ioctl_compat: handle FITRIM 2015-07-09 11:42:21 -07:00
nls
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notify fsnotify: fix oops in fsnotify_clear_marks_by_group_flags() 2015-08-07 04:39:41 +03:00
ntfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2015-07-04 19:36:06 -07:00
ocfs2 ocfs2: fix shift left overflow 2015-08-07 04:39:41 +03:00
omfs omfs: fix potential integer overflow in allocator 2015-05-28 18:25:19 -07:00
openpromfs
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overlayfs fix a braino in ovl_d_select_inode() 2015-07-12 11:22:05 -04:00
proc Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2015-07-18 10:49:57 -07:00
pstore Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2015-07-03 15:20:57 -07:00
qnx4
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qnx6 pagemap.h: move dir_pages() over there 2015-06-23 18:02:00 -04:00
quota Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2015-04-26 17:22:07 -07:00
ramfs VFS: normal filesystems (and lustre): d_inode() annotations 2015-04-15 15:06:57 -04:00
reiserfs Merge branch 'akpm' (patches from Andrew) 2015-06-26 09:52:05 -07:00
romfs make new_sync_{read,write}() static 2015-04-11 22:29:40 -04:00
squashfs fs: cleanup slight list_entry abuse 2015-06-23 18:01:59 -04:00
sysfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2015-07-03 15:20:57 -07:00
sysv pagemap.h: move dir_pages() over there 2015-06-23 18:02:00 -04:00
tracefs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2015-07-04 19:36:06 -07:00
ubifs This pull request includes the following UBI/UBIFS changes: 2015-06-25 14:11:34 -07:00
udf udf: Don't corrupt unalloc spacetable when writing it 2015-07-09 16:38:57 +02:00
ufs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2015-07-04 19:36:06 -07:00
xfs xfs: remote attributes need to be considered data 2015-07-29 11:48:02 +10:00
Kconfig f2fs: relocate Kconfig from misc filesystems 2015-04-10 15:08:35 -07:00
Kconfig.binfmt mm: split ET_DYN ASLR from mmap ASLR 2015-04-14 16:49:05 -07:00
Makefile um: Remove hppfs 2015-05-31 13:23:08 +02:00
aio.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2015-04-16 23:27:56 -04:00
anon_inodes.c
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attr.c
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bad_inode.c don't bother with most of the bad_file_ops methods 2015-02-20 04:03:58 -05:00
binfmt_aout.c assorted conversions to %p[dD] 2014-11-19 13:01:20 -05:00
binfmt_elf.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2015-07-04 19:36:06 -07:00
binfmt_elf_fdpic.c handle suicide on late failure exits in execve() in search_binary_handler() 2014-10-09 02:39:00 -04:00
binfmt_em86.c syscalls: implement execveat() system call 2014-12-13 12:42:51 -08:00
binfmt_flat.c
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binfmt_misc.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2015-04-26 17:22:07 -07:00
binfmt_script.c syscalls: implement execveat() system call 2014-12-13 12:42:51 -08:00
block_dev.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2015-07-04 19:36:06 -07:00
buffer.c buffer: remove unusued 'ret' variable 2015-06-02 09:22:34 -06:00
char_dev.c fs: introduce f_op->mmap_capabilities for nommu mmap support 2015-01-20 14:02:58 -07:00
compat.c vfs: make first argument of dir_context.actor typed 2014-10-31 17:48:54 -04:00
compat_binfmt_elf.c
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compat_ioctl.c ioctl_compat: handle FITRIM 2015-07-09 11:42:21 -07:00
coredump.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2015-07-04 19:36:06 -07:00
dax.c xfs: call dax_fault on read page faults for DAX 2015-07-29 11:48:00 +10:00
dcache.c fs, file table: reinit files_stat.max_files after deferred memory initialisation 2015-08-07 04:39:40 +03:00
dcookies.c
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direct-io.c direct-io: only inc/dec inode->i_dio_count for file systems 2015-04-24 15:45:28 -04:00
drop_caches.c vmscan: per memory cgroup slab shrinkers 2015-02-12 18:54:09 -08:00
eventfd.c eventfd: don't take the spinlock in eventfd_poll 2015-02-17 14:34:52 -08:00
eventpoll.c epoll: optimize setting task running after blocking 2015-02-13 21:21:40 -08:00
exec.c parisc,metag: Fix crashes due to stack randomization on stack-grows-upwards architectures 2015-05-12 22:03:44 +02:00
fcntl.c vfs: renumber FMODE_NONOTIFY and add to uniqueness check 2015-01-08 15:10:52 -08:00
fhandle.c vfs: read file_handle only once in handle_to_path 2015-06-02 10:29:07 -07:00
file.c fs/file.c: __fget() and dup2() atomicity rules 2015-07-01 02:31:08 -04:00
file_table.c fs, file table: reinit files_stat.max_files after deferred memory initialisation 2015-08-07 04:39:40 +03:00
filesystems.c
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fs-writeback.c writeback: plug writeback at a high level 2015-08-17 18:39:45 -04:00
fs_pin.c fs_pin: Allow for the possibility that m_list or s_list go unused. 2015-04-09 11:39:55 -05:00
fs_struct.c
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inode.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2015-07-04 19:36:06 -07:00
internal.h overlayfs: Make f_path always point to the overlay and f_inode to the underlay 2015-06-19 03:19:32 -04:00
ioctl.c fsioctl.c: make generic_block_fiemap() signal-tolerant 2015-02-10 14:30:30 -08:00
libfs.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2015-07-04 19:36:06 -07:00
locks.c locks: inline posix_lock_file_wait and flock_lock_file_wait 2015-07-13 06:29:11 -04:00
mbcache.c
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mount.h fs: use seq_open_private() for proc_mounts 2015-06-30 19:44:56 -07:00
mpage.c writeback: implement foreign cgroup inode detection 2015-06-02 08:40:20 -06:00
namei.c may_follow_link() should use nd->inode 2015-08-04 23:23:50 -04:00
namespace.c mnt: In detach_mounts detach the appropriate unmounted mount 2015-07-23 11:31:15 -05:00
no-block.c
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nsfs.c VFS: assorted weird filesystems: d_inode() annotations 2015-04-15 15:06:58 -04:00
open.c fs: Call security_ops->inode_killpriv on truncate 2015-06-23 18:01:09 -04:00
pipe.c VFS: assorted weird filesystems: d_inode() annotations 2015-04-15 15:06:58 -04:00
pnode.c mnt: Don't propagate unmounts to locked mounts 2015-04-02 20:34:20 -05:00
pnode.h mnt: Clarify and correct the disconnect logic in umount_tree 2015-07-22 20:33:27 -05:00
posix_acl.c fs/posix_acl.c: make posix_acl_create() safer and cleaner 2015-06-23 18:01:07 -04:00
proc_namespace.c fs: use seq_open_private() for proc_mounts 2015-06-30 19:44:56 -07:00
read_write.c new_sync_write(): discard ->ki_pos unless the return value is positive 2015-04-11 22:29:46 -04:00
readdir.c vfs: make first argument of dir_context.actor typed 2014-10-31 17:48:54 -04:00
select.c locking/arch: Rename set_mb() to smp_store_mb() 2015-05-19 08:32:00 +02:00
seq_file.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2015-07-04 19:36:06 -07:00
signalfd.c signalfd: fix information leak in signalfd_copyinfo 2015-08-07 04:39:40 +03:00
splice.c Merge branch 'akpm' (patches from Andrew) 2015-06-24 20:47:21 -07:00
stack.c fs: fix comment for 'CONFIG_LBADF' 2014-08-26 09:35:56 +02:00
stat.c VFS: assorted d_backing_inode() annotations 2015-04-15 15:06:59 -04:00
statfs.c
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super.c fs:super:get_anon_bdev: fix race condition could cause dev exceed its upper limitation 2015-07-01 01:50:06 -04:00
sync.c vfs: add support for a lazytime mount option 2015-02-05 02:45:00 -05:00
timerfd.c fs: Convert show_fdinfo functions to void 2014-11-05 14:13:23 -05:00
utimes.c
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xattr.c evm: fix potential race when removing xattrs 2015-05-21 13:28:47 -04:00