From: Nick Piggin <npiggin@kernel.dk>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Nick Piggin <npiggin@kernel.dk>,
Dave Chinner <david@fromorbit.com>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: Inode Lock Scalability V7 (was V6)
Date: Fri, 22 Oct 2010 15:48:12 +1100 [thread overview]
Message-ID: <20101022044812.GB6899@amd> (raw)
In-Reply-To: <20101022031211.GI19804@ZenIV.linux.org.uk>
On Fri, Oct 22, 2010 at 04:12:11AM +0100, Al Viro wrote:
> On Fri, Oct 22, 2010 at 01:48:34PM +1100, Nick Piggin wrote:
> > On Fri, Oct 22, 2010 at 01:41:52PM +1100, Nick Piggin wrote:
> > > The locking in my lock break patch is ugly and wrong, yes. But it is
> > > always an intermediate step. I want to argue that with RCU inode work
> > > *anyway*, there is not much point to reducing the strength of the
> > > i_lock property because locking can be cleaned up nicely and still
> > > keep i_lock ~= inode_lock (for a single inode).
> >
> > The other thing is that with RCU, the idea of locking an object in
> > the data structure with a per object lock actually *is* much more
> > natural. It's hard to do it properly with just a big data structure
> > lock.
> >
> > If I want to take a reference to an inode from a data structre, how
> > to do it with RCU?
> >
> > rcu_read_lock()
> > list_for_each(inode) {
> > spin_lock(&big_lock); /* oops, might as well not even use RCU then */
> > if (!unhashed) {
> > iget();
> > }
> > }
>
> Huh? Why the hell does it have to be a big lock? You grab ->i_lock,
> then look at the damn thing. You also grab it on eviction from the
> list - *inside* the lock used for serializing the write access to
> your RCU list.
That sucks, it requires more acquiring and dropping of i_lock and
it hits single threaded performance. I looked at that.
But it also loses the i_lock = inode_lock property.
next prev parent reply other threads:[~2010-10-22 4:48 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-21 0:49 Inode Lock Scalability V6 Dave Chinner
2010-10-21 0:49 ` [PATCH 01/21] fs: switch bdev inode bdi's correctly Dave Chinner
2010-10-21 0:49 ` [PATCH 02/21] kernel: add bl_list Dave Chinner
2010-10-21 0:49 ` [PATCH 03/21] fs: Convert nr_inodes and nr_unused to per-cpu counters Dave Chinner
2010-10-21 0:49 ` [PATCH 04/21] fs: Implement lazy LRU updates for inodes Dave Chinner
2010-10-21 2:14 ` Christian Stroetmann
2010-10-21 10:07 ` Nick Piggin
2010-10-21 12:22 ` Christoph Hellwig
2010-10-23 9:32 ` Al Viro
2010-10-21 0:49 ` [PATCH 05/21] fs: inode split IO and LRU lists Dave Chinner
2010-10-21 0:49 ` [PATCH 06/21] fs: Clean up inode reference counting Dave Chinner
2010-10-21 1:41 ` Christoph Hellwig
2010-10-21 0:49 ` [PATCH 07/21] exofs: use iput() for inode reference count decrements Dave Chinner
2010-10-21 0:49 ` [PATCH 08/21] fs: rework icount to be a locked variable Dave Chinner
2010-10-21 19:40 ` Al Viro
2010-10-21 22:32 ` Dave Chinner
2010-10-21 0:49 ` [PATCH 09/21] fs: Factor inode hash operations into functions Dave Chinner
2010-10-21 0:49 ` [PATCH 10/21] fs: Stop abusing find_inode_fast in iunique Dave Chinner
2010-10-21 0:49 ` [PATCH 11/21] fs: move i_ref increments into find_inode/find_inode_fast Dave Chinner
2010-10-21 0:49 ` [PATCH 12/21] fs: remove inode_add_to_list/__inode_add_to_list Dave Chinner
2010-10-21 0:49 ` [PATCH 13/21] fs: Introduce per-bucket inode hash locks Dave Chinner
2010-10-21 0:49 ` [PATCH 14/21] fs: add a per-superblock lock for the inode list Dave Chinner
2010-10-21 0:49 ` [PATCH 15/21] fs: split locking of inode writeback and LRU lists Dave Chinner
2010-10-21 0:49 ` [PATCH 16/21] fs: Protect inode->i_state with the inode->i_lock Dave Chinner
2010-10-22 1:56 ` Al Viro
2010-10-22 2:26 ` Nick Piggin
2010-10-22 3:14 ` Dave Chinner
2010-10-22 10:37 ` Al Viro
2010-10-22 11:40 ` Christoph Hellwig
2010-10-23 21:40 ` Al Viro
2010-10-23 21:37 ` Al Viro
2010-10-24 14:13 ` Christoph Hellwig
2010-10-24 16:21 ` Christoph Hellwig
2010-10-24 19:17 ` Al Viro
2010-10-24 20:04 ` Christoph Hellwig
2010-10-24 20:36 ` Al Viro
2010-10-24 2:18 ` Nick Piggin
2010-10-21 0:49 ` [PATCH 17/21] fs: protect wake_up_inode with inode->i_lock Dave Chinner
2010-10-21 2:17 ` Christoph Hellwig
2010-10-21 13:16 ` Nick Piggin
2010-10-21 0:49 ` [PATCH 18/21] fs: introduce a per-cpu last_ino allocator Dave Chinner
2010-10-21 0:49 ` [PATCH 19/21] fs: icache remove inode_lock Dave Chinner
2010-10-21 2:14 ` Christian Stroetmann
2010-10-21 0:49 ` [PATCH 20/21] fs: Reduce inode I_FREEING and factor inode disposal Dave Chinner
2010-10-21 0:49 ` [PATCH 21/21] fs: do not assign default i_ino in new_inode Dave Chinner
2010-10-21 5:04 ` Inode Lock Scalability V7 (was V6) Dave Chinner
2010-10-21 13:20 ` Nick Piggin
2010-10-21 23:52 ` Dave Chinner
2010-10-22 0:45 ` Nick Piggin
2010-10-22 2:20 ` Al Viro
2010-10-22 2:34 ` Nick Piggin
2010-10-22 2:41 ` Nick Piggin
2010-10-22 2:48 ` Nick Piggin
2010-10-22 3:12 ` Al Viro
2010-10-22 4:48 ` Nick Piggin [this message]
2010-10-22 3:07 ` Al Viro
2010-10-22 4:46 ` Nick Piggin
2010-10-22 5:01 ` Nick Piggin
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