From: Christoph Hellwig <hch@infradead.org>
To: Dave Chinner <david@fromorbit.com>
Cc: xfs@oss.sgi.com
Subject: Re: [PATCH 05/18] xfs: convert inode cache lookups to use RCU locking
Date: Tue, 14 Sep 2010 12:27:42 -0400 [thread overview]
Message-ID: <20100914162742.GA18185@infradead.org> (raw)
In-Reply-To: <1284461777-1496-6-git-send-email-david@fromorbit.com>
On Tue, Sep 14, 2010 at 08:56:04PM +1000, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
>
> With delayed logging greatly increasing the sustained parallelism of inode
> operations, the inode cache locking is showing significant read vs write
> contention when inode reclaim runs at the same time as lookups. There is
> also a lot more write lock acquistions than there are read locks (4:1 ratio)
> so the read locking is not really buying us much in the way of parallelism.
That's just for your parallel creates workload, isn't it? If we'd get
that bad hit rates on normal workloads something is pretty wrong with
the inode cache.
For a workload with 4 times as many writelocks just changing the
rwlock to a spinlock should provide more benefits. Did you test what
effect this has on other workloads?
In addition to that I feel really uneasy about changes to the inode
cache locking without really heavy NFS server testing - we just had too
many issues in this area in the past.
> To avoid the read vs write contention, change the cache to use RCU locking on
> the read side. To avoid needing to RCU free every single inode, use the built
> in slab RCU freeing mechanism. This requires us to be able to detect lookups of
> freed inodes, so en??ure that ever freed inode has an inode number of zero and
> the XFS_IRECLAIM flag set. We already check the XFS_IRECLAIM flag in cache hit
> lookup path, but also add a check for a zero inode number as well.
How does this interact with slab poisoning?
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next prev parent reply other threads:[~2010-09-14 16:29 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-14 10:55 [PATCH 0/18] xfs: metadata and buffer cache scalability improvements Dave Chinner
2010-09-14 10:56 ` [PATCH 01/18] xfs: single thread inode cache shrinking Dave Chinner
2010-09-14 18:48 ` Alex Elder
2010-09-14 22:48 ` Dave Chinner
2010-09-14 10:56 ` [PATCH 02/18] xfs: reduce the number of CIL lock round trips during commit Dave Chinner
2010-09-14 14:48 ` Christoph Hellwig
2010-09-14 17:21 ` Alex Elder
2010-09-14 10:56 ` [PATCH 03/18] xfs: remove debug assert for per-ag reference counting Dave Chinner
2010-09-14 14:48 ` Christoph Hellwig
2010-09-14 17:22 ` Alex Elder
2010-09-14 10:56 ` [PATCH 04/18] xfs: lockless per-ag lookups Dave Chinner
2010-09-14 12:35 ` Dave Chinner
2010-09-14 14:50 ` Christoph Hellwig
2010-09-14 17:28 ` Alex Elder
2010-09-14 10:56 ` [PATCH 05/18] xfs: convert inode cache lookups to use RCU locking Dave Chinner
2010-09-14 16:27 ` Christoph Hellwig [this message]
2010-09-14 23:17 ` Dave Chinner
2010-09-14 21:23 ` Alex Elder
2010-09-14 23:42 ` Dave Chinner
2010-09-14 10:56 ` [PATCH 06/18] xfs: convert pag_ici_lock to a spin lock Dave Chinner
2010-09-14 21:26 ` Alex Elder
2010-09-14 10:56 ` [PATCH 07/18] xfs: don't use vfs writeback for pure metadata modifications Dave Chinner
2010-09-14 14:54 ` Christoph Hellwig
2010-09-15 0:14 ` Dave Chinner
2010-09-15 0:17 ` Christoph Hellwig
2010-09-14 22:12 ` Alex Elder
2010-09-15 0:28 ` Dave Chinner
2010-11-08 10:47 ` Christoph Hellwig
2010-09-14 10:56 ` [PATCH 08/18] xfs: rename xfs_buf_get_nodaddr to be more appropriate Dave Chinner
2010-09-14 14:56 ` Christoph Hellwig
2010-09-14 22:14 ` Alex Elder
2010-09-14 10:56 ` [PATCH 09/18] xfs: introduced uncached buffer read primitve Dave Chinner
2010-09-14 14:56 ` Christoph Hellwig
2010-09-14 22:16 ` Alex Elder
2010-09-14 10:56 ` [PATCH 10/18] xfs: store xfs_mount in the buftarg instead of in the xfs_buf Dave Chinner
2010-09-14 14:57 ` Christoph Hellwig
2010-09-14 22:21 ` Alex Elder
2010-09-14 10:56 ` [PATCH 11/18] xfs: kill XBF_FS_MANAGED buffers Dave Chinner
2010-09-14 14:59 ` Christoph Hellwig
2010-09-14 22:26 ` Alex Elder
2010-09-14 10:56 ` [PATCH 12/18] xfs: use unhashed buffers for size checks Dave Chinner
2010-09-14 15:00 ` Christoph Hellwig
2010-09-14 22:29 ` Alex Elder
2010-09-14 10:56 ` [PATCH 13/18] xfs: remove buftarg hash for external devices Dave Chinner
2010-09-14 22:29 ` Alex Elder
2010-09-14 10:56 ` [PATCH 14/18] xfs: convert buffer cache hash to rbtree Dave Chinner
2010-09-14 16:29 ` Christoph Hellwig
2010-09-15 17:46 ` Alex Elder
2010-09-14 10:56 ` [PATCH 15/18] xfs; pack xfs_buf structure more tightly Dave Chinner
2010-09-14 16:30 ` Christoph Hellwig
2010-09-15 18:01 ` Alex Elder
2010-09-14 10:56 ` [PATCH 16/18] xfs: convert xfsbud shrinker to a per-buftarg shrinker Dave Chinner
2010-09-14 16:32 ` Christoph Hellwig
2010-09-15 20:19 ` Alex Elder
2010-09-16 0:28 ` Dave Chinner
2010-09-14 10:56 ` [PATCH 17/18] xfs: add a lru to the XFS buffer cache Dave Chinner
2010-09-14 23:16 ` Christoph Hellwig
2010-09-15 0:05 ` Dave Chinner
2010-09-15 21:28 ` Alex Elder
2010-09-14 10:56 ` [PATCH 18/18] xfs: stop using the page cache to back the " Dave Chinner
2010-09-14 23:20 ` Christoph Hellwig
2010-09-15 0:06 ` Dave Chinner
2010-09-14 14:25 ` [PATCH 0/18] xfs: metadata and buffer cache scalability improvements Christoph Hellwig
2010-09-17 13:21 ` Alex Elder
2010-09-21 2:02 ` Dave Chinner
2010-09-21 16:23 ` Alex Elder
2010-09-21 22:34 ` Dave Chinner
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