linux-kernel - Re: [PATCH 29/32] block, aio: Batch completion for bios/kiocbs

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Date:	Tue, 8 Jan 2013 08:48:24 -0800
From:	Kent Overstreet <koverstreet@...gle.com>
To:	Jeff Moyer <jmoyer@...hat.com>
Cc:	Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org,
	linux-aio@...ck.org, linux-fsdevel@...r.kernel.org, zab@...hat.com,
	bcrl@...ck.org, viro@...iv.linux.org.uk, tytso@....edu
Subject: Re: [PATCH 29/32] block, aio: Batch completion for bios/kiocbs

On Tue, Jan 08, 2013 at 11:15:37AM -0500, Jeff Moyer wrote:
> Kent Overstreet <koverstreet@...gle.com> writes:
> 
> > On Tue, Jan 08, 2013 at 10:33:18AM -0500, Jeff Moyer wrote:
> >> Kent Overstreet <koverstreet@...gle.com> writes:
> >> 
> >> >> Is the rbtree really faster than a basic (l)list and a sort before
> >> >> completing them? Would be simpler.
> >> >
> >> > Well, depends. With one or two kioctxs? The list would definitely be
> >> > faster, but I'm loathe to use an O(n^2) algorithm anywhere where the
> >> > input size isn't strictly controlled, and I know of applications out
> >> > there that use tons of kioctxs.
> >> 
> >> Out of curiosity, what applications do you know of that use tons of
> >> kioctx's?
> >
> > "tons" is relative I suppose, but before this patch series sharing a
> > kioctx between threads was really bad for performance and... you know
> > how people can be with threads.
> 
> I wasn't questioning the merits of the patch, I was simply curious to
> know how aio is being (ab)used in the wild.  So, is this some internal
> tool, then, or what?

Oh, didn't think you were, I just never looked for actual numbers. Yeah,
some internal library code is what I was referring to, but from the
story of how it evolved I don't think it's unusual.
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