linux-kernel - Re: [PATCH 22/33] aio: percpu reqs

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Message-ID: <20130402160317.GF31577@thunk.org>
Date:	Tue, 2 Apr 2013 12:03:17 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Kent Overstreet <koverstreet@...gle.com>
Cc:	linux-kernel@...r.kernel.org, linux-aio@...ck.org,
	akpm@...ux-foundation.org, Zach Brown <zab@...hat.com>,
	Felipe Balbi <balbi@...com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Mark Fasheh <mfasheh@...e.com>,
	Joel Becker <jlbec@...lplan.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Jens Axboe <axboe@...nel.dk>,
	Asai Thambi S P <asamymuthupa@...ron.com>,
	Selvan Mani <smani@...ron.com>,
	Sam Bradshaw <sbradshaw@...ron.com>,
	Jeff Moyer <jmoyer@...hat.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Benjamin LaHaise <bcrl@...ck.org>
Subject: Re: [PATCH 22/33] aio: percpu reqs_available

On Thu, Mar 21, 2013 at 09:35:43AM -0700, Kent Overstreet wrote:
> See the previous patch ("aio: reqs_active -> reqs_available") for why we
> want to do this - this basically implements a per cpu allocator for
> reqs_available that doesn't actually allocate anything.
> 
> Note that we need to increase the size of the ringbuffer we allocate,
> since a single thread won't necessarily be able to use all the
> reqs_available slots - some (up to about half) might be on other per cpu
> lists, unavailable for the current thread.
> 
> We size the ringbuffer based on the nr_events userspace passed to
> io_setup(), so this is a slight behaviour change - but nr_events wasn't
> being used as a hard limit before, it was being rounded up to the next
> page before so this doesn't change the actual semantics.

Reviewed-by: "Theodore Ts'o" <tytso@....edu>

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