Large streaming reads make for large bios, which means each entry on the
list async work queues represents a large amount of data. IO
congestion throttling on the device was kicking in before the async
worker threads decided a single thread was busy and needed some help.
The end result was that a streaming read would result in a single CPU
running at 100% instead of balancing the work off to other CPUs.
This patch also changes the pre-IO checksum lookup done by reads to
work on a per-bio basis instead of a per-page. This results in many
extra btree lookups on large streaming reads. Doing the checksum lookup
right before bio submit allows us to reuse searches while processing
adjacent offsets.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
The memory reclaiming issue happens when snapshot exists. In that
case, some cache entries may not be used during old snapshot dropping,
so they will remain in the cache until umount.
The patch adds a field to struct btrfs_leaf_ref to record create time. Besides,
the patch makes all dead roots of a given snapshot linked together in order of
create time. After a old snapshot was completely dropped, we check the dead
root list and remove all cache entries created before the oldest dead root in
the list.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
It was possible for stale mappings from disk to be used instead of the
new pending ordered extent. This adds a flag to the extent map struct
to keep it pinned until the pending ordered extent is actually on disk.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
Data checksumming is done right before the bio is sent down the IO stack,
which means a single bio might span more than one ordered extent. In
this case, the checksumming data is split between two ordered extents.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
The old data=ordered code would force commit to wait until
all the data extents from the transaction were fully on disk. This
introduced large latencies into the commit and stalled new writers
in the transaction for a long time.
The new code changes the way data allocations and extents work:
* When delayed allocation is filled, data extents are reserved, and
the extent bit EXTENT_ORDERED is set on the entire range of the extent.
A struct btrfs_ordered_extent is allocated an inserted into a per-inode
rbtree to track the pending extents.
* As each page is written EXTENT_ORDERED is cleared on the bytes corresponding
to that page.
* When all of the bytes corresponding to a single struct btrfs_ordered_extent
are written, The previously reserved extent is inserted into the FS
btree and into the extent allocation trees. The checksums for the file
data are also updated.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
This significantly improves streaming write performance by allowing
concurrency in the data checksumming.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
When we checkum file data during writepage, the checksumming is done one
page at a time, making it difficult to do bulk metadata modifications
to insert checksums for large ranges of the file at once.
This patch changes btrfs to checksum on a per-bio basis instead. The
bios are checksummed before they are handed off to the block layer, so
each bio is contiguous and only has pages from the same inode.
Checksumming on a bio basis allows us to insert and modify the file
checksum items in large groups. It also allows the checksumming to
be done more easily by async worker threads.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
The fixes do a number of things:
1) Most btrfs_drop_extent callers will try to leave the inline extents in
place. It can truncate bytes off the beginning of the inline extent if
required.
2) writepage can now update the inline extent, allowing mmap writes to
go directly into the inline extent.
3) btrfs_truncate_in_transaction truncates inline extents
4) extent_map.c fixed to not merge inline extent mappings and hole
mappings together
Signed-off-by: Chris Mason <chris.mason@oracle.com>
Execution should goto label 'insert' when 'btrfs_next_leaf' return a
non-zero value, otherwise the parameter 'slot' for
'btrfs_item_key_to_cpu' may be out of bounds. The original codes jump
to label 'insert' only when 'btrfs_next_leaf' return a negative
value.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
This reduces the number of calls to btrfs_extend_item and greatly lowers
the cpu usage while writing large files.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
Almost none of the files including module.h need to do so,
remove them.
Include sched.h in extent-tree.c to silence a warning about cond_resched()
being undeclared.
Signed-off-by: Zach Brown <zach.brown@oracle.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
Attaching below is some of the code cleanups that i came across while
reading the code.
a) alloc_path already calls init_path.
b) Mention that btrfs_inode is the in memory copy.Ext4 have ext4_inode_info as
the in memory copy ext4_inode as the disk copy
Signed-off-by: Chris Mason <chris.mason@oracle.com>
Chris Mason