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Date: Mon, 1 Apr 2013 22:53:50 -0400
From: "Theodore Ts'o" <tytso@mit.edu>
To: Kent Overstreet <koverstreet@google.com>
Cc: linux-kernel@vger.kernel.org, linux-aio@kvack.org,
        akpm@linux-foundation.org, Zach Brown <zab@redhat.com>,
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        Jeff Moyer <jmoyer@redhat.com>, Al Viro <viro@zeniv.linux.org.uk>,
        Benjamin LaHaise <bcrl@kvack.org>
Subject: Re: [PATCH 17/33] aio: change reqs_active to include unreaped
 completions
Message-ID: <20130402025350.GF30122@thunk.org>
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	Asai Thambi S P <asamymuthupa@micron.com>,
	Selvan Mani <smani@micron.com>, Sam Bradshaw <sbradshaw@micron.com>,
	Jeff Moyer <jmoyer@redhat.com>, Al Viro <viro@zeniv.linux.org.uk>,
	Benjamin LaHaise <bcrl@kvack.org>
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On Thu, Mar 21, 2013 at 09:35:38AM -0700, Kent Overstreet wrote:
> The aio code tries really hard to avoid having to deal with the completion
> ringbuffer overflowing.  To do that, it has to keep track of the number of
> outstanding kiocbs, and the number of completions currently in the
> ringbuffer - and it's got to check that every time we allocate a kiocb.
> Ouch.
> 
> But - we can improve this quite a bit if we just change reqs_active to
> mean "number of outstanding requests and unreaped completions" - that
> means kiocb allocation doesn't have to look at the ringbuffer, which is a
> fairly significant win.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

Could you please add a quick comment documenting the reqs_active field
in the struct kioctx definition here?  For future code
maintainability, it should be documented in fs/aio.c, not just in a
commit description.

>  struct kioctx {
>  	atomic_t		users;
>  	atomic_t		dead;
> @@ -92,7 +86,13 @@ struct kioctx {
>  	atomic_t		reqs_active;
>  	struct list_head	active_reqs;	/* used for cancellation */

	       					   - Ted
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