[PATCH 1/5] Add AIO event ring size tunable

["Sébastien Dugué" <sebastien.dugue@bull.net>]

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aiomaxevents :

 This patch adds a posix_aio_default_maxevents sysctl variable for configuring the
default AIO context event ring size at runtime. This way, calling sys_io_setup with
nr_events=0, will result in the kernel using the default system value.

 This tunable is accessible via /proc/sys/fs/posix-aio-default-max-nr.

 Makefile               |    2 +-
 fs/Kconfig             |    8 ++++++++
 fs/aio.c               |    8 ++++++++
 include/linux/aio.h    |    3 +++
 include/linux/sysctl.h |    3 +++
 kernel/sysctl.c        |   10 ++++++++++
 6 files changed, 33 insertions(+), 1 deletion(-)

Signed-off-by: Sébastien Dugué <sebastien.dugue@bull.net>

Index: linux-2.6.12/fs/aio.c
===================================================================
--- linux-2.6.12.orig/fs/aio.c	2005-06-23 13:58:03.000000000 +0200
+++ linux-2.6.12/fs/aio.c	2005-06-23 13:59:08.000000000 +0200
@@ -43,6 +43,9 @@
 /*------ sysctl variables----*/
 atomic_t aio_nr = ATOMIC_INIT(0);	/* current system wide number of aio requests */
 unsigned aio_max_nr = 0x10000;	/* system wide maximum number of aio requests */
+#if defined(CONFIG_POSIX_AIO)
+unsigned posix_aio_default_maxevents = 1024; /* FIXME: default value for POSIX AIO */
+#endif /* CONFIG_POSIX_AIO */
 /*----end sysctl variables---*/
 
 static kmem_cache_t	*kiocb_cachep;
@@ -1244,6 +1247,11 @@
 	unsigned long ctx;
 	long ret;
 
+#if defined(CONFIG_POSIX_AIO)
+	if (nr_events == 0)
+		nr_events = posix_aio_default_maxevents;
+#endif
+
 	ret = get_user(ctx, ctxp);
 	if (unlikely(ret))
 		goto out;
Index: linux-2.6.12/fs/Kconfig
===================================================================
--- linux-2.6.12.orig/fs/Kconfig	2005-06-23 13:58:03.000000000 +0200
+++ linux-2.6.12/fs/Kconfig	2005-06-23 13:59:08.000000000 +0200
@@ -4,6 +4,14 @@
 
 menu "File systems"
 
+config POSIX_AIO
+	bool "POSIX AIO Support"
+	help
+	  Enable POSIX Asynchronous IO
+
+	  If unsure, say N.
+
+
 config EXT2_FS
 	tristate "Second extended fs support"
 	help
Index: linux-2.6.12/include/linux/aio.h
===================================================================
--- linux-2.6.12.orig/include/linux/aio.h	2005-06-23 13:58:03.000000000 +0200
+++ linux-2.6.12/include/linux/aio.h	2005-06-23 13:59:08.000000000 +0200
@@ -153,6 +153,9 @@
 
 /* prototypes */
 extern unsigned aio_max_size;
+#if defined(CONFIG_POSIX_AIO)
+extern unsigned posix_aio_default_maxevents;
+#endif /* CONFIG_POSIX_AIO */
 
 extern ssize_t FASTCALL(wait_on_sync_kiocb(struct kiocb *iocb));
 extern int FASTCALL(aio_put_req(struct kiocb *iocb));
Index: linux-2.6.12/include/linux/sysctl.h
===================================================================
--- linux-2.6.12.orig/include/linux/sysctl.h	2005-06-23 13:58:03.000000000 +0200
+++ linux-2.6.12/include/linux/sysctl.h	2005-06-23 13:59:08.000000000 +0200
@@ -680,6 +680,9 @@
 	FS_XFS=17,	/* struct: control xfs parameters */
 	FS_AIO_NR=18,	/* current system-wide number of aio requests */
 	FS_AIO_MAX_NR=19,	/* system-wide maximum number of aio requests */
+#if defined(CONFIG_POSIX_AIO)
+	FS_POSIX_AIO_MAX_NR=20,	/* default value for POSIX AIO max request */
+#endif /* CONFIG_POSIX_AIO */
 };
 
 /* /proc/sys/fs/quota/ */
Index: linux-2.6.12/kernel/sysctl.c
===================================================================
--- linux-2.6.12.orig/kernel/sysctl.c	2005-06-23 13:58:03.000000000 +0200
+++ linux-2.6.12/kernel/sysctl.c	2005-06-23 13:59:08.000000000 +0200
@@ -949,6 +949,16 @@
 		.mode		= 0644,
 		.proc_handler	= &proc_dointvec,
 	},
+#if defined(CONFIG_POSIX_AIO)
+	{
+		.ctl_name	= FS_POSIX_AIO_MAX_NR,
+		.procname	= "posix-aio-default-max-nr",
+		.data		= &posix_aio_default_maxevents,
+		.maxlen		= sizeof(posix_aio_default_maxevents),
+		.mode		= 0644,
+		.proc_handler	= &proc_dointvec,
+	},
+#endif /* CONFIG_POSIX_AIO */
 #endif
 	{ .ctl_name = 0 }
 };
Index: linux-2.6.12/Makefile
===================================================================
--- linux-2.6.12.orig/Makefile	2005-06-23 13:58:03.000000000 +0200
+++ linux-2.6.12/Makefile	2005-06-23 13:59:08.000000000 +0200
@@ -1,7 +1,7 @@
 VERSION = 2
 PATCHLEVEL = 6
 SUBLEVEL = 12
-EXTRAVERSION =
+EXTRAVERSION = .PAIO-aiomaxevents
 NAME=Woozy Numbat
 
 # *DOCUMENTATION*