On 01/21/2013 07:53 AM, Dave Chinner wrote: > From: Dave Chinner <dchinner@xxxxxxxxxx> > > There is a window on small filesytsems where specualtive > preallocation can be larger than that ENOSPC throttling thresholds, > resulting in specualtive preallocation trying to reserve more space > than there is space available. This causes immediate ENOSPC to be > triggered, prealloc to be turned off and flushing to occur. One the > next write (i.e. next 4k page), we do exactly the same thing, and so > effective drive into synchronous 4k writes by triggering ENOSPC > flushing on every page while in the window between the prealloc size > and the ENOSPC prealloc throttle threshold. > > Fix this by checking to see if the prealloc size would consume all > free space, and throttle it appropriately to avoid premature > ENOSPC... > Would this alternatively be resolved by the updated throttling code that is part of my quota prealloc throttling set? I'm referring to the following patch in particular: http://oss.sgi.com/archives/xfs/2013-01/msg00003.html Brian > Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx> > --- > fs/xfs/xfs_iomap.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c > index 3587772..de3bad5 100644 > --- a/fs/xfs/xfs_iomap.c > +++ b/fs/xfs/xfs_iomap.c > @@ -395,6 +395,15 @@ xfs_iomap_prealloc_size( > } > if (shift) > alloc_blocks >>= shift; > + > + /* > + * If we are still trying to allocate more space than is > + * available, squash the prealloc hard. This can happen if we > + * have a large file on a small filesystem and the above > + * lowspace thresholds are smaller than MAXEXTLEN. > + */ > + while (alloc_blocks >= freesp) > + alloc_blocks >>= 4; > } > > if (alloc_blocks < mp->m_writeio_blocks) > _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
