On Tue, 2010-09-14 at 20:56 +1000, Dave Chinner wrote: > From: Dave Chinner <dchinner@xxxxxxxxxx> > > The buffer cache hash is showing typical hash scalability problems. > In large scale testing the number of cached items growing far larger > than the hash can efficiently handle. Hence we need to move to a > self-scaling cache indexing mechanism. > > I have selected rbtrees for indexing becuse they can have O(log n) > search scalability, and insert and remove cost is not excessive, > even on large trees. Hence we should be able to cache large numbers > of buffers without incurring the excessive cache miss search > penalties that the hash is imposing on us. > > To ensure we still have parallel access to the cache, we need > multiple trees. Rather than hashing the buffers by disk address to > select a tree, it seems more sensible to separate trees by typical > access patterns. Most operations use buffers from within a single AG > at a time, so rather than searching lots of different lists, > separate the buffer indexes out into per-AG rbtrees. This means that > searches during metadata operation have a much higher chance of > hitting cache resident nodes, and that updates of the tree are less > likely to disturb trees being accessed on other CPUs doing > independent operations. I didn't review this time as carefully as I did when you originally posted this. Some parts from the original are now in separate patches. But this looks good to me. Reviewed-by: Alex Elder <aelder@xxxxxxx> > Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx> > --- > fs/xfs/linux-2.6/xfs_buf.c | 138 +++++++++++++++++++++---------------------- > fs/xfs/linux-2.6/xfs_buf.h | 8 +-- > fs/xfs/xfs_ag.h | 4 + > fs/xfs/xfs_mount.c | 2 + > 4 files changed, 75 insertions(+), 77 deletions(-) . . . _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
