Re: [PATCH v1 0/8] Deferred dput() and iput() -- reducing lock contention

From: Andi Kleen
Date: Wed Jan 21 2009 - 00:53:25 EST

Mike Waychison <mikew@xxxxxxxxxx> writes:

> livelock on dcache_lock/inode_lock (specifically in atomic_dec_and_lock())

I'm not sure how something can livelock in atomic_dec_and_lock which
doesn't take a spinlock itself? Are you saying you run into NUMA memory
unfairness here? Or did I misparse you?

> This patchset is an attempt to try and reduce the locking overheads associated
> with final dput() and final iput(). This is done by batching dentries and
> inodes into per-process queues and processing them in 'parallel' to consolidate
> some of the locking.

I was wondering what this does to the latencies when dput/iput
is only done for very objects. Does it increase costs then

As a high level comment it seems like a lot of work to work
around global locks, like the inode_lock, where it might be better to
just split the lock up? Mind you I don't have a clear proposal
how to do that, but surely it's doable somehow.


ak@xxxxxxxxxxxxxxx -- Speaking for myself only.
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