Author: delphij
Date: Mon Sep 28 16:59:47 2009
New Revision: 197579
URL: http://svn.freebsd.org/changeset/base/197579
Log:
Add two new fcntls to enable/disable read-ahead:
- F_READAHEAD: specify the amount for sequential access. The amount is
specified in bytes and is rounded up to nearest block size.
- F_RDAHEAD: Darwin compatible version that use 128KB as the sequential
access size.
A third argument of zero disables the read-ahead behavior.
Please note that the read-ahead amount is also constrainted by sysctl
variable, vfs.read_max, which may need to be raised in order to better
utilize this feature.
Thanks Igor Sysoev for proposing the feature and submitting the original
version, and kib@ for his valuable comments.
Submitted by: Igor Sysoev <is rambler-co ru>
Reviewed by: kib@
MFC after: 1 month
Modified:
head/lib/libc/sys/fcntl.2
head/sys/kern/kern_descrip.c
head/sys/kern/vfs_vnops.c
head/sys/sys/fcntl.h
Modified: head/lib/libc/sys/fcntl.2
==============================================================================
--- head/lib/libc/sys/fcntl.2 Mon Sep 28 15:11:49 2009 (r197578)
+++ head/lib/libc/sys/fcntl.2 Mon Sep 28 16:59:47 2009 (r197579)
@@ -28,7 +28,7 @@
.\" @(#)fcntl.2 8.2 (Berkeley) 1/12/94
.\" $FreeBSD$
.\"
-.Dd March 8, 2008
+.Dd September 28, 2009
.Dt FCNTL 2
.Os
.Sh NAME
@@ -241,6 +241,22 @@ will be interrupted if the signal handle
.Dv SA_RESTART
(see
.Xr sigaction 2 ) .
+.It Dv F_READAHEAD
+Set or clear the read ahead amount for sequential access to the third
+argument,
+.Fa arg ,
+which is rounded up to the nearest block size.
+A zero value in
+.Fa arg
+turns off read ahead.
+.It Dv F_RDAHEAD
+Equivalent to Darwin counterpart which sets read ahead amount of 128KB
+when the third argument,
+.Fa arg
+is non-zero.
+A zero value in
+.Fa arg
+turns off read ahead.
.El
.Pp
When a shared lock has been set on a segment of a file,
Modified: head/sys/kern/kern_descrip.c
==============================================================================
--- head/sys/kern/kern_descrip.c Mon Sep 28 15:11:49 2009
(r197578)
+++ head/sys/kern/kern_descrip.c Mon Sep 28 16:59:47 2009
(r197579)
@@ -421,6 +421,8 @@ kern_fcntl(struct thread *td, int fd, in
struct vnode *vp;
int error, flg, tmp;
int vfslocked;
+ u_int old, new;
+ uint64_t bsize;
vfslocked = 0;
error = 0;
@@ -686,6 +688,48 @@ kern_fcntl(struct thread *td, int fd, in
vfslocked = 0;
fdrop(fp, td);
break;
+
+ case F_RDAHEAD:
+ arg = arg ? 128 * 1024: 0;
+ /* FALLTHROUGH */
+ case F_READAHEAD:
+ FILEDESC_SLOCK(fdp);
+ if ((fp = fdtofp(fd, fdp)) == NULL) {
+ FILEDESC_SUNLOCK(fdp);
+ error = EBADF;
+ break;
+ }
+ if (fp->f_type != DTYPE_VNODE) {
+ FILEDESC_SUNLOCK(fdp);
+ error = EBADF;
+ break;
+ }
+ fhold(fp);
+ FILEDESC_SUNLOCK(fdp);
+ if (arg != 0) {
+ vp = fp->f_vnode;
+ vfslocked = VFS_LOCK_GIANT(vp->v_mount);
+ error = vn_lock(vp, LK_SHARED);
+ if (error != 0)
+ goto readahead_vnlock_fail;
+ bsize = fp->f_vnode->v_mount->mnt_stat.f_iosize;
+ VOP_UNLOCK(vp, 0);
+ fp->f_seqcount = (arg + bsize - 1) / bsize;
+ do {
+ new = old = fp->f_flag;
+ new |= FRDAHEAD;
+ } while (atomic_cmpset_rel_int(&fp->f_flag, old, new)
== 0);
+readahead_vnlock_fail:
+ VFS_UNLOCK_GIANT(vfslocked);
+ } else {
+ do {
+ new = old = fp->f_flag;
+ new &= ~FRDAHEAD;
+ } while (atomic_cmpset_rel_int(&fp->f_flag, old, new)
== 0);
+ }
+ fdrop(fp, td);
+ break;
+
default:
error = EINVAL;
break;
Modified: head/sys/kern/vfs_vnops.c
==============================================================================
--- head/sys/kern/vfs_vnops.c Mon Sep 28 15:11:49 2009 (r197578)
+++ head/sys/kern/vfs_vnops.c Mon Sep 28 16:59:47 2009 (r197579)
@@ -312,6 +312,9 @@ static int
sequential_heuristic(struct uio *uio, struct file *fp)
{
+ if (atomic_load_acq_int(&(fp->f_flag)) & FRDAHEAD)
+ return (fp->f_seqcount << IO_SEQSHIFT);
+
/*
* Offset 0 is handled specially. open() sets f_seqcount to 1 so
* that the first I/O is normally considered to be slightly
Modified: head/sys/sys/fcntl.h
==============================================================================
--- head/sys/sys/fcntl.h Mon Sep 28 15:11:49 2009 (r197578)
+++ head/sys/sys/fcntl.h Mon Sep 28 16:59:47 2009 (r197579)
@@ -140,7 +140,7 @@ typedef __pid_t pid_t;
/* bits to save after open */
#define FMASK
(FREAD|FWRITE|FAPPEND|FASYNC|FFSYNC|FNONBLOCK|O_DIRECT|FEXEC)
/* bits settable by fcntl(F_SETFL, ...) */
-#define FCNTLFLAGS (FAPPEND|FASYNC|FFSYNC|FNONBLOCK|O_DIRECT)
+#define FCNTLFLAGS
(FAPPEND|FASYNC|FFSYNC|FNONBLOCK|FRDAHEAD|O_DIRECT)
#if defined(COMPAT_FREEBSD7) || defined(COMPAT_FREEBSD6) || \
defined(COMPAT_FREEBSD5) || defined(COMPAT_FREEBSD4)
@@ -151,7 +151,8 @@ typedef __pid_t pid_t;
*/
#define FPOSIXSHM O_NOFOLLOW
#undef FCNTLFLAGS
-#define FCNTLFLAGS
(FAPPEND|FASYNC|FFSYNC|FNONBLOCK|FPOSIXSHM|O_DIRECT)
+#define FCNTLFLAGS
(FAPPEND|FASYNC|FFSYNC|FNONBLOCK|FPOSIXSHM|FRDAHEAD| \
+ O_DIRECT)
#endif
#endif
@@ -176,6 +177,8 @@ typedef __pid_t pid_t;
* different meaning for fcntl(2).
*/
#if __BSD_VISIBLE
+/* Read ahead */
+#define FRDAHEAD O_CREAT
#endif
/* Defined by POSIX Extended API Set Part 2 */
@@ -218,6 +221,8 @@ typedef __pid_t pid_t;
#define F_SETLK 12 /* set record locking
information */
#define F_SETLKW 13 /* F_SETLK; wait if blocked */
#define F_SETLK_REMOTE 14 /* debugging support for remote
locks */
+#define F_READAHEAD 15 /* read ahead */
+#define F_RDAHEAD 16 /* Darwin compatible read ahead
*/
/* file descriptor flags (F_GETFD, F_SETFD) */
#define FD_CLOEXEC 1 /* close-on-exec flag */
_______________________________________________
svn-src-all@freebsd.org mailing list
http://lists.freebsd.org/mailman/listinfo/svn-src-all
To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"
