linux-kernel - Re: [patch] convert aio event reap to use atomic-op instead of spin

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Date:	Thu, 12 Apr 2007 18:08:56 -0700
From:	"Ken Chen" <kenchen@...gle.com>
To:	"Jeff Moyer" <jmoyer@...hat.com>
Cc:	"Zach Brown" <zach.brown@...cle.com>, akpm@...ux-foundation.org,
	linux-aio@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [patch] convert aio event reap to use atomic-op instead of spin_lock

On 4/12/07, Ken Chen <kenchen@...gle.com> wrote:
> On 4/12/07, Jeff Moyer <jmoyer@...hat.com> wrote:
> > I didn't see any response to Zach's request for code that actually
> > tests out the shared ring buffer.  Do you have such code?
>
> Yes, I do.  I was stress testing the code since last night.  After 20+
> hours of stress run with fio and aio-stress, now I'm posting it with
> confidence.
>
> I modified libaio's io_getevents to take advantage of new user level
> reap function. The feature is exported out via ring->compat_features.
> btw, is compat_feature suppose to be a version number or a bit mask?
> I think bitmask make more sense and more flexible.

Additional patch on the kernel side to export the new features.  On
top of patch posted at:
http://marc.info/?l=linux-kernel&m=117636401818057&w=2

--- a/include/linux/aio.h
+++ b/include/linux/aio.h
@@ -138,8 +138,11 @@ #define init_sync_kiocb(x, filp)			\
 		init_wait((&(x)->ki_wait));             \
 	} while (0)

+#define AIO_RING_BASE		1
+#define AIO_RING_USER_REAP	2
+
 #define AIO_RING_MAGIC			0xa10a10a1
-#define AIO_RING_COMPAT_FEATURES	1
+#define AIO_RING_COMPAT_FEATURES	(AIO_RING_BASE | AIO_RING_USER_REAP)
 #define AIO_RING_INCOMPAT_FEATURES	0
 struct aio_ring {
 	unsigned	id;	/* kernel internal index number */
-
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