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  1. 15 10月, 2007 1 次提交
  3. 14 7月, 2007 4 次提交
    • D
      [XFS] Concurrent Multi-File Data Streams · 2a82b8be
      由 David Chinner 提交于 
      In media spaces, video is often stored in a frame-per-file format. When
dealing with uncompressed realtime HD video streams in this format, it is
crucial that files do not get fragmented and that multiple files a placed
contiguously on disk.

When multiple streams are being ingested and played out at the same time,
it is critical that the filesystem does not cross the streams and
interleave them together as this creates seek and readahead cache miss
latency and prevents both ingest and playout from meeting frame rate
targets.

This patch set creates a "stream of files" concept into the allocator to
place all the data from a single stream contiguously on disk so that RAID
array readahead can be used effectively. Each additional stream gets
placed in different allocation groups within the filesystem, thereby
ensuring that we don't cross any streams. When an AG fills up, we select a
new AG for the stream that is not in use.

The core of the functionality is the stream tracking - each inode that we
create in a directory needs to be associated with the directories' stream.
Hence every time we create a file, we look up the directories' stream
object and associate the new file with that object.

Once we have a stream object for a file, we use the AG that the stream
object point to for allocations. If we can't allocate in that AG (e.g. it
is full) we move the entire stream to another AG. Other inodes in the same
stream are moved to the new AG on their next allocation (i.e. lazy
update).

Stream objects are kept in a cache and hold a reference on the inode.
Hence the inode cannot be reclaimed while there is an outstanding stream
reference. This means that on unlink we need to remove the stream
association and we also need to flush all the associations on certain
events that want to reclaim all unreferenced inodes (e.g. filesystem
freeze).

SGI-PV: 964469
SGI-Modid: xfs-linux-melb:xfs-kern:29096a
Signed-off-by: NDavid Chinner <dgc@sgi.com>
Signed-off-by: NBarry Naujok <bnaujok@sgi.com>
Signed-off-by: NDonald Douwsma <donaldd@sgi.com>
Signed-off-by: NChristoph Hellwig <hch@infradead.org>
Signed-off-by: NTim Shimmin <tes@sgi.com>
Signed-off-by: NVlad Apostolov <vapo@sgi.com>
      2a82b8be
    • D
      [XFS] Fix remount,readonly path to flush everything correctly. · 516b2e7c
      由 David Chinner 提交于 
      The remount readonly path can fail to writeback properly because we still
have active transactions after calling xfs_quiesce_fs(). Further
investigation shows that this path is broken in the same ways that the xfs
freeze path was broken so fix it the same way.

SGI-PV: 964464
SGI-Modid: xfs-linux-melb:xfs-kern:28869a
Signed-off-by: NDavid Chinner <dgc@sgi.com>
Signed-off-by: NChristoph Hellwig <hch@infradead.org>
Signed-off-by: NTim Shimmin <tes@sgi.com>
      516b2e7c
    • D
      [XFS] Lazy Superblock Counters · 92821e2b
      由 David Chinner 提交于 
      When we have a couple of hundred transactions on the fly at once, they all
typically modify the on disk superblock in some way.
create/unclink/mkdir/rmdir modify inode counts, allocation/freeing modify
free block counts.

When these counts are modified in a transaction, they must eventually lock
the superblock buffer and apply the mods. The buffer then remains locked
until the transaction is committed into the incore log buffer. The result
of this is that with enough transactions on the fly the incore superblock
buffer becomes a bottleneck.

The result of contention on the incore superblock buffer is that
transaction rates fall - the more pressure that is put on the superblock
buffer, the slower things go.

The key to removing the contention is to not require the superblock fields
in question to be locked. We do that by not marking the superblock dirty
in the transaction. IOWs, we modify the incore superblock but do not
modify the cached superblock buffer. In short, we do not log superblock
modifications to critical fields in the superblock on every transaction.
In fact we only do it just before we write the superblock to disk every
sync period or just before unmount.

This creates an interesting problem - if we don't log or write out the
fields in every transaction, then how do the values get recovered after a
crash? the answer is simple - we keep enough duplicate, logged information
in other structures that we can reconstruct the correct count after log
recovery has been performed.

It is the AGF and AGI structures that contain the duplicate information;
after recovery, we walk every AGI and AGF and sum their individual
counters to get the correct value, and we do a transaction into the log to
correct them. An optimisation of this is that if we have a clean unmount
record, we know the value in the superblock is correct, so we can avoid
the summation walk under normal conditions and so mount/recovery times do
not change under normal operation.

One wrinkle that was discovered during development was that the blocks
used in the freespace btrees are never accounted for in the AGF counters.
This was once a valid optimisation to make; when the filesystem is full,
the free space btrees are empty and consume no space. Hence when it
matters, the "accounting" is correct. But that means the when we do the
AGF summations, we would not have a correct count and xfs_check would
complain. Hence a new counter was added to track the number of blocks used
by the free space btrees. This is an *on-disk format change*.

As a result of this, lazy superblock counters are a mkfs option and at the
moment on linux there is no way to convert an old filesystem. This is
possible - xfs_db can be used to twiddle the right bits and then
xfs_repair will do the format conversion for you. Similarly, you can
convert backwards as well. At some point we'll add functionality to
xfs_admin to do the bit twiddling easily....

SGI-PV: 964999
SGI-Modid: xfs-linux-melb:xfs-kern:28652a
Signed-off-by: NDavid Chinner <dgc@sgi.com>
Signed-off-by: NChristoph Hellwig <hch@infradead.org>
Signed-off-by: NTim Shimmin <tes@sgi.com>
      92821e2b
    • D
      [XFS] Sleeping with the ilock waiting for I/O completion is Bad. · 40095b64
      由 David Chinner 提交于 
      Recent fixes to the filesystem freezing code introduced a vn_iowait call
in the middle of the sync code. Unfortunately, at the point where this
call was added we are holding the ilock. The ilock is needed by I/O
completion for unwritten extent conversion and now updating the file size.
Hence I/o cannot complete if we hold the ilock while waiting for I/O
completion.

Fix up the bug and clean the code up around it.

SGI-PV: 963674
SGI-Modid: xfs-linux-melb:xfs-kern:28566a
Signed-off-by: NDavid Chinner <dgc@sgi.com>
Signed-off-by: NChristoph Hellwig <hch@infradead.org>
Signed-off-by: NTim Shimmin <tes@sgi.com>
      40095b64
  5. 08 5月, 2007 3 次提交
  7. 10 2月, 2007 4 次提交
  9. 28 9月, 2006 1 次提交
  11. 07 9月, 2006 1 次提交
    • D
      [XFS] Prevent free space oversubscription and xfssyncd looping. · 4be536de
      由 David Chinner 提交于 
      The fix for recent ENOSPC deadlocks introduced certain limitations on
allocations. The fix could cause xfssyncd to loop endlessly if we did not
leave some space free for the allocator to work correctly. Basically, we
needed to ensure that we had at least 4 blocks free for an AG free list
and a block for the inode bmap btree at all times.

However, this did not take into account the fact that each AG has a free
list that needs 4 blocks. Hence any filesystem with more than one AG could
cause oversubscription of free space and make xfssyncd spin forever trying
to allocate space needed for AG freelists that was not available in the
AG.

The following patch reserves space for the free lists in all AGs plus the
inode bmap btree which prevents oversubscription. It also prevents those
blocks from being reported as free space (as they can never be used) and
makes the SMP in-core superblock accounting code and the reserved block
ioctl respect this requirement.

SGI-PV: 955674
SGI-Modid: xfs-linux-melb:xfs-kern:26894a
Signed-off-by: NDavid Chinner <dgc@sgi.com>
Signed-off-by: NDavid Chatterton <chatz@sgi.com>
      4be536de
  13. 28 7月, 2006 1 次提交
  15. 20 6月, 2006 1 次提交
  17. 09 6月, 2006 5 次提交
  19. 08 5月, 2006 1 次提交
  21. 31 3月, 2006 2 次提交
  23. 29 3月, 2006 1 次提交
  25. 22 3月, 2006 2 次提交
  27. 17 3月, 2006 1 次提交
  29. 14 3月, 2006 3 次提交
  31. 11 1月, 2006 7 次提交
  33. 04 11月, 2005 1 次提交
  35. 02 11月, 2005 1 次提交