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author | delphij <delphij@FreeBSD.org> | 2009-09-28 16:59:47 +0000 |
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committer | delphij <delphij@FreeBSD.org> | 2009-09-28 16:59:47 +0000 |
commit | 79f2f8c774b48d4ef62f92d4a09e80af3ceaca7c (patch) | |
tree | 1cca7c0ea10e2ad0213a1d75a2c8a8fe0061f4d4 /lib | |
parent | fd5f08e3e82b6caa8a7fff6a32c9e56b9212003e (diff) | |
download | FreeBSD-src-79f2f8c774b48d4ef62f92d4a09e80af3ceaca7c.zip FreeBSD-src-79f2f8c774b48d4ef62f92d4a09e80af3ceaca7c.tar.gz |
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
Diffstat (limited to 'lib')
-rw-r--r-- | lib/libc/sys/fcntl.2 | 18 |
1 files changed, 17 insertions, 1 deletions
diff --git a/lib/libc/sys/fcntl.2 b/lib/libc/sys/fcntl.2 index a16724c..250cef4 100644 --- a/lib/libc/sys/fcntl.2 +++ b/lib/libc/sys/fcntl.2 @@ -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 handler has not specified the .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, |