On Thu, Sep 17, 2009 at 03:50:36PM -0700, Alfred Perlstein wrote:
> Please do not make the option have the same name but different
> semantics.
>
> Strongly suggest adding the Darwin name as a toggle and a FreeBSD
> name as a specific size option.
Then it may be:
case F_RDAHEAD:
arg = arg ? 128 * 1024: 0;
/* FALLTHROUGH F_READAHEAD */
case F_READAHEAD:
> -Alfred
>
> * Xin LI <delp...@delphij.net> [090917 15:27] wrote:
> > -----BEGIN PGP SIGNED MESSAGE-----
> > Hash: SHA1
> >
> > Hi, Igor,
> >
> > Igor Sysoev wrote:
> > > Hi,
> > >
> > > nginx-0.8.15 can use completely non-blocking sendfile() using SF_NODISKIO
> > > flag. When sendfile() returns EBUSY, nginx calls aio_read() to read single
> > > byte. The first aio_read() preloads the first 128K part of a file in VM
> > > cache,
> > > however, all successive aio_read()s preload just 16K parts of the file.
> > > This makes non-blocking sendfile() usage ineffective for files larger
> > > than 128K.
> > >
> > > I've created a small patch for Darwin compatible F_RDAHEAD fcntl:
> > >
> > > fcntl(fd, F_RDAHEAD, preload_size)
> > >
> > > There is small incompatibilty: Darwin's fcntl allows just to
> > > enable/disable
> > > read ahead, while the proposed patch allows to set exact preload size.
> > >
> > > Currently the preload size affects vn_read() code path only and does not
> > > affect on sendfile() code path. However, it can be easy extended on
> > > sendfile() part too. The preload size is still limited by sysctl
> > > vfs.read_max.
> > >
> > > The patch is against FreeBSD 7.2 and was tested on FreeBSD 7.2-STABLE
> > > only.
> >
> > I have ported this as a patch against -HEAD (should apply on 8.0-R but
> > it's too late for us to add a new feature) plus a manual page entry
> > documenting the feature.
> >
> > I've used F_READAHEAD as the name, but reading the manual page, it looks
> > like we can just use F_RDAHEAD since Darwin seems to just distinguish 0
> > and !=0 case so that programmers won't have to use #ifdef or something
> > else to get code working on different platform?
> >
> > Cheers,
> > - --
> > Xin LI <delp...@delphij.net> http://www.delphij.net/
> > FreeBSD - The Power to Serve!
> > -----BEGIN PGP SIGNATURE-----
> > Version: GnuPG v2.0.12 (FreeBSD)
> >
> > iEYEARECAAYFAkqyt40ACgkQi+vbBBjt66AdKgCfXOo/Vn+zw0cCjS+gGJUgPo8t
> > WToAmgKIXaVKsKUcqVOqTwHl4eTFsbkM
> > =uP3m
> > -----END PGP SIGNATURE-----
>
> > Index: lib/libc/sys/fcntl.2
> > ===================================================================
> > --- lib/libc/sys/fcntl.2 (revision 197297)
> > +++ lib/libc/sys/fcntl.2 (working copy)
> > @@ -28,7 +28,7 @@
> > .\" @(#)fcntl.2 8.2 (Berkeley) 1/12/94
> > .\" $FreeBSD$
> > .\"
> > -.Dd March 8, 2008
> > +.Dd September 19, 2009
> > .Dt FCNTL 2
> > .Os
> > .Sh NAME
> > @@ -241,6 +241,14 @@
> > .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.
> > .El
> > .Pp
> > When a shared lock has been set on a segment of a file,
> > Index: sys/kern/kern_descrip.c
> > ===================================================================
> > --- sys/kern/kern_descrip.c (revision 197297)
> > +++ sys/kern/kern_descrip.c (working copy)
> > @@ -421,6 +421,7 @@
> > struct vnode *vp;
> > int error, flg, tmp;
> > int vfslocked;
> > + uint64_t bsize;
> >
> > vfslocked = 0;
> > error = 0;
> > @@ -686,6 +687,31 @@
> > vfslocked = 0;
> > fdrop(fp, td);
> > break;
> > +
> > + 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) {
> > + bsize = fp->f_vnode->v_mount->mnt_stat.f_iosize;
> > + fp->f_seqcount = (arg + bsize - 1) / bsize;
> > + fp->f_flag |= O_READAHEAD;
> > + } else {
> > + fp->f_flag &= ~O_READAHEAD;
> > + }
> > + fdrop(fp, td);
> > + break;
> > +
> > default:
> > error = EINVAL;
> > break;
> > Index: sys/kern/vfs_vnops.c
> > ===================================================================
> > --- sys/kern/vfs_vnops.c (revision 197297)
> > +++ sys/kern/vfs_vnops.c (working copy)
> > @@ -312,6 +312,9 @@
> > sequential_heuristic(struct uio *uio, struct file *fp)
> > {
> >
> > + if (fp->f_flag & O_READAHEAD)
> > + 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
> > Index: sys/sys/fcntl.h
> > ===================================================================
> > --- sys/sys/fcntl.h (revision 197297)
> > +++ sys/sys/fcntl.h (working copy)
> > @@ -112,7 +112,11 @@
> > #if __BSD_VISIBLE
> > /* Attempt to bypass buffer cache */
> > #define O_DIRECT 0x00010000
> > +#ifdef _KERNEL
> > +/* Read ahead */
> > +#define O_READAHEAD 0x00020000
> > #endif
> > +#endif
> >
> > /* Defined by POSIX Extended API Set Part 2 */
> > #if __BSD_VISIBLE
> > @@ -218,6 +222,7 @@
> > #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 */
> >
> > /* file descriptor flags (F_GETFD, F_SETFD) */
> > #define FD_CLOEXEC 1 /* close-on-exec flag */
>
> > _______________________________________________
> > freebsd-hackers@freebsd.org mailing list
> > http://lists.freebsd.org/mailman/listinfo/freebsd-hackers
> > To unsubscribe, send any mail to "freebsd-hackers-unsubscr...@freebsd.org"
>
> --
> - Alfred Perlstein
> .- AMA, VMOA #5191, 03 vmax, 92 gs500, 85 ch250
> .- FreeBSD committer
--
Igor Sysoev
http://sysoev.ru/en/
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