1. 24 Mar, 2009 11 commits
    • Chris Mason's avatar
      Btrfs: readahead checksums during btrfs_finish_ordered_io · 5d13a98f
      Chris Mason authored
      
      
      This reads in blocks in the checksum btree before starting the
      transaction in btrfs_finish_ordered_io.  It makes it much more likely
      we'll be able to do operations inside the transaction without
      needing any btree reads, which limits transaction latencies overall.
      Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
      5d13a98f
    • Chris Mason's avatar
      Btrfs: leave btree locks spinning more often · b9473439
      Chris Mason authored
      
      
      btrfs_mark_buffer dirty would set dirty bits in the extent_io tree
      for the buffers it was dirtying.  This may require a kmalloc and it
      was not atomic.  So, anyone who called btrfs_mark_buffer_dirty had to
      set any btree locks they were holding to blocking first.
      
      This commit changes dirty tracking for extent buffers to just use a flag
      in the extent buffer.  Now that we have one and only one extent buffer
      per page, this can be safely done without losing dirty bits along the way.
      
      This also introduces a path->leave_spinning flag that callers of
      btrfs_search_slot can use to indicate they will properly deal with a
      path returned where all the locks are spinning instead of blocking.
      
      Many of the btree search callers now expect spinning paths,
      resulting in better btree concurrency overall.
      Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
      b9473439
    • Chris Mason's avatar
      Btrfs: Only let very young transactions grow during commit · 89573b9c
      Chris Mason authored
      
      
      Commits are fairly expensive, and so btrfs has code to sit around for a while
      during the commit and let new writers come in.
      
      But, while we're sitting there, new delayed refs might be added, and those
      can be expensive to process as well.  Unless the transaction is very very
      young, it makes sense to go ahead and let the commit finish without hanging
      around.
      
      The commit grow loop isn't as important as it used to be, the fsync logging
      code handles most performance critical syncs now.
      Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
      89573b9c
    • Chris Mason's avatar
      Btrfs: Check for a blocking lock before taking the spin · 66d7e85e
      Chris Mason authored
      
      
      This reduces contention on the extent buffer spin locks by testing for a
      blocking lock before trying to take the spinlock.
      Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
      66d7e85e
    • Chris Mason's avatar
      Btrfs: reduce stack in cow_file_range · 7f366cfe
      Chris Mason authored
      
      
      The fs/btrfs/inode.c code to run delayed allocation during writout
      needed some stack usage optimization.  This is the first pass, it does
      the check for compression earlier on, which allows us to do the common
      (no compression) case higher up in the call chain.
      Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
      7f366cfe
    • Chris Mason's avatar
      Btrfs: reduce stalls during transaction commit · b7ec40d7
      Chris Mason authored
      
      
      To avoid deadlocks and reduce latencies during some critical operations, some
      transaction writers are allowed to jump into the running transaction and make
      it run a little longer, while others sit around and wait for the commit to
      finish.
      
      This is a bit unfair, especially when the callers that jump in do a bunch
      of IO that makes all the others procs on the box wait.  This commit
      reduces the stalls this produces by pre-reading file extent pointers
      during btrfs_finish_ordered_io before the transaction is joined.
      
      It also tunes the drop_snapshot code to politely wait for transactions
      that have started writing out their delayed refs to finish.  This avoids
      new delayed refs being flooded into the queue while we're trying to
      close off the transaction.
      Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
      b7ec40d7
    • Chris Mason's avatar
      Btrfs: process the delayed reference queue in clusters · c3e69d58
      Chris Mason authored
      
      
      The delayed reference queue maintains pending operations that need to
      be done to the extent allocation tree.  These are processed by
      finding records in the tree that are not currently being processed one at
      a time.
      
      This is slow because it uses lots of time searching through the rbtree
      and because it creates lock contention on the extent allocation tree
      when lots of different procs are running delayed refs at the same time.
      
      This commit changes things to grab a cluster of refs for processing,
      using a cursor into the rbtree as the starting point of the next search.
      This way we walk smoothly through the rbtree.
      Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
      c3e69d58
    • Chris Mason's avatar
      Btrfs: try to cleanup delayed refs while freeing extents · 1887be66
      Chris Mason authored
      
      
      When extents are freed, it is likely that we've removed the last
      delayed reference update for the extent.  This checks the delayed
      ref tree when things are freed, and if no ref updates area left it
      immediately processes the delayed ref.
      Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
      1887be66
    • Chris Mason's avatar
      Btrfs: reduce stack usage in some crucial tree balancing functions · 44871b1b
      Chris Mason authored
      
      
      Many of the tree balancing functions follow the same pattern.
      
      1) cow a block
      2) do something to the result
      
      This commit breaks them up into two functions so the variables and
      code required for part two don't suck down stack during part one.
      Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
      44871b1b
    • Chris Mason's avatar
      Btrfs: do extent allocation and reference count updates in the background · 56bec294
      Chris Mason authored
      
      
      The extent allocation tree maintains a reference count and full
      back reference information for every extent allocated in the
      filesystem.  For subvolume and snapshot trees, every time
      a block goes through COW, the new copy of the block adds a reference
      on every block it points to.
      
      If a btree node points to 150 leaves, then the COW code needs to go
      and add backrefs on 150 different extents, which might be spread all
      over the extent allocation tree.
      
      These updates currently happen during btrfs_cow_block, and most COWs
      happen during btrfs_search_slot.  btrfs_search_slot has locks held
      on both the parent and the node we are COWing, and so we really want
      to avoid IO during the COW if we can.
      
      This commit adds an rbtree of pending reference count updates and extent
      allocations.  The tree is ordered by byte number of the extent and byte number
      of the parent for the back reference.  The tree allows us to:
      
      1) Modify back references in something close to disk order, reducing seeks
      2) Significantly reduce the number of modifications made as block pointers
      are balanced around
      3) Do all of the extent insertion and back reference modifications outside
      of the performance critical btrfs_search_slot code.
      
      #3 has the added benefit of greatly reducing the btrfs stack footprint.
      The extent allocation tree modifications are done without the deep
      (and somewhat recursive) call chains used in the past.
      
      These delayed back reference updates must be done before the transaction
      commits, and so the rbtree is tied to the transaction.  Throttling is
      implemented to help keep the queue of backrefs at a reasonable size.
      
      Since there was a similar mechanism in place for the extent tree
      extents, that is removed and replaced by the delayed reference tree.
      
      Yan Zheng <yan.zheng@oracle.com> helped review and fixup this code.
      Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
      56bec294
    • Chris Mason's avatar
      Btrfs: don't preallocate metadata blocks during btrfs_search_slot · 9fa8cfe7
      Chris Mason authored
      
      
      In order to avoid doing expensive extent management with tree locks held,
      btrfs_search_slot will preallocate tree blocks for use by COW without
      any tree locks held.
      
      A later commit moves all of the extent allocation work for COW into
      a delayed update mechanism, and this preallocation will no longer be
      required.
      Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
      9fa8cfe7
  2. 23 Mar, 2009 8 commits
  3. 22 Mar, 2009 9 commits
  4. 21 Mar, 2009 2 commits
  5. 20 Mar, 2009 5 commits
  6. 19 Mar, 2009 5 commits