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The following script from Wu Fengguang shows very bad behaviour in XFS
when aggressively dirtying data during a sync on XFS, with sync times
up to almost 10 times as long as ext4.
A large part of the issue is that XFS writes data out itself two times
in the ->sync_fs method, overriding the livelock protection in the core
writeback code, and another issue is the lock-less xfs_ioend_wait call,
which doesn't prevent new ioend from being queue up while waiting for
the count to reach zero.
This patch removes the XFS-internal sync calls and relies on the VFS
to do it's work just like all other filesystems do. Note that the
i_iocount wait which is rather suboptimal is simply removed here.
We already do it in ->write_inode, which keeps the current supoptimal
behaviour. We'll eventually need to remove that as well, but that's
material for a separate commit.
------------------------------ snip ------------------------------
#!/bin/sh
umount /dev/sda7
mkfs.xfs -f /dev/sda7
# mkfs.ext4 /dev/sda7
# mkfs.btrfs /dev/sda7
mount /dev/sda7 /fs
echo $((50<<20)) > /proc/sys/vm/dirty_bytes
pid=
for i in `seq 10`
do
dd if=/dev/zero of=/fs/zero-$i bs=1M count=1000 &
pid="$pid $!"
done
sleep 1
tic=$(date +'%s')
sync
tac=$(date +'%s')
echo
echo sync time: $((tac-tic))
egrep '(Dirty|Writeback|NFS_Unstable)' /proc/meminfo
pidof dd > /dev/null && { kill -9 $pid; echo sync NOT livelocked; }
------------------------------ snip ------------------------------
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reported-by: Wu Fengguang <fengguang.wu@intel.com>
Reviewed-by: Alex Elder <aelder@sgi.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
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|---|---|---|
| .. | ||
| linux-2.6 | ||
| quota | ||
| support | ||
| Kconfig | ||
| Makefile | ||
| xfs_acl.h | ||
| xfs_ag.h | ||
| xfs_alloc_btree.c | ||
| xfs_alloc_btree.h | ||
| xfs_alloc.c | ||
| xfs_alloc.h | ||
| xfs_arch.h | ||
| xfs_attr_leaf.c | ||
| xfs_attr_leaf.h | ||
| xfs_attr_sf.h | ||
| xfs_attr.c | ||
| xfs_attr.h | ||
| xfs_bit.c | ||
| xfs_bit.h | ||
| xfs_bmap_btree.c | ||
| xfs_bmap_btree.h | ||
| xfs_bmap.c | ||
| xfs_bmap.h | ||
| xfs_btree_trace.c | ||
| xfs_btree_trace.h | ||
| xfs_btree.c | ||
| xfs_btree.h | ||
| xfs_buf_item.c | ||
| xfs_buf_item.h | ||
| xfs_da_btree.c | ||
| xfs_da_btree.h | ||
| xfs_dfrag.c | ||
| xfs_dfrag.h | ||
| xfs_dinode.h | ||
| xfs_dir2_block.c | ||
| xfs_dir2_block.h | ||
| xfs_dir2_data.c | ||
| xfs_dir2_data.h | ||
| xfs_dir2_leaf.c | ||
| xfs_dir2_leaf.h | ||
| xfs_dir2_node.c | ||
| xfs_dir2_node.h | ||
| xfs_dir2_sf.c | ||
| xfs_dir2_sf.h | ||
| xfs_dir2.c | ||
| xfs_dir2.h | ||
| xfs_error.c | ||
| xfs_error.h | ||
| xfs_extfree_item.c | ||
| xfs_extfree_item.h | ||
| xfs_filestream.c | ||
| xfs_filestream.h | ||
| xfs_fs.h | ||
| xfs_fsops.c | ||
| xfs_fsops.h | ||
| xfs_ialloc_btree.c | ||
| xfs_ialloc_btree.h | ||
| xfs_ialloc.c | ||
| xfs_ialloc.h | ||
| xfs_iget.c | ||
| xfs_inode_item.c | ||
| xfs_inode_item.h | ||
| xfs_inode.c | ||
| xfs_inode.h | ||
| xfs_inum.h | ||
| xfs_iomap.c | ||
| xfs_iomap.h | ||
| xfs_itable.c | ||
| xfs_itable.h | ||
| xfs_log_cil.c | ||
| xfs_log_priv.h | ||
| xfs_log_recover.c | ||
| xfs_log_recover.h | ||
| xfs_log.c | ||
| xfs_log.h | ||
| xfs_mount.c | ||
| xfs_mount.h | ||
| xfs_mru_cache.c | ||
| xfs_mru_cache.h | ||
| xfs_quota.h | ||
| xfs_rename.c | ||
| xfs_rtalloc.c | ||
| xfs_rtalloc.h | ||
| xfs_rw.c | ||
| xfs_rw.h | ||
| xfs_sb.h | ||
| xfs_trans_ail.c | ||
| xfs_trans_buf.c | ||
| xfs_trans_extfree.c | ||
| xfs_trans_inode.c | ||
| xfs_trans_priv.h | ||
| xfs_trans_space.h | ||
| xfs_trans.c | ||
| xfs_trans.h | ||
| xfs_types.h | ||
| xfs_utils.c | ||
| xfs_utils.h | ||
| xfs_vnodeops.c | ||
| xfs_vnodeops.h | ||
| xfs.h | ||