linux-kernel - Re: [PATCH 4/5] aio: vmap ringbuffer

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Message-ID: <20121009223210.GR26187@lenny.home.zabbo.net>
Date:	Tue, 9 Oct 2012 15:32:10 -0700
From:	Zach Brown <zab@...hat.com>
To:	Kent Overstreet <koverstreet@...gle.com>
Cc:	linux-bcache@...r.kernel.org, linux-kernel@...r.kernel.org,
	dm-devel@...hat.com, tytso@....edu
Subject: Re: [PATCH 4/5] aio: vmap ringbuffer

> If it is measurable I'll take another stab at using memory from
> __get_free_pages() for the ringbuffer. That really would be the ideal
> solution.

No, then you'll run into high order allocation failures with rings that
don't fit in a single page.

> The other reason I wanted to do this was for the aio attributes stuff -
> for return values, I think the only sane way is for the return values to
> go in the ringbuffer, which means records are no longer fixed size so
> dealing with pages is even more of a pain.

Then let's see that, please.

And can we please stop calling them attributes?  They're inputs and
outputs that change behaviour -- they're interfaces.

And no, just for the record, I don't think generic packed variable size
structs are worth the trouble.

If we're going to do a generic interface extension mechanism then we
should put it in its own well thought out system calls, not staple it on
to the side of aio because it's there.  It's a really crummy base to
work from.

- z
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