From 00125c972600955205ae24c7a58053ec94b649db Mon Sep 17 00:00:00 2001
From: Charles Kerr <charles@transmissionbt.com>
Date: Sun, 25 Jan 2009 23:33:10 +0000
Subject: [PATCH] (trunk libT) add mac, linux, and win32 support for os-level
 hints that local data will be read in random order, to disable readahead
 buffering.

---
 configure.ac              | 12 ++++++++++++
 libtransmission/fdlimit.c | 10 ++++++++++
 2 files changed, 22 insertions(+)

diff --git a/configure.ac b/configure.ac
index 45b443f94..a07ca0b4f 100644
--- a/configure.ac
+++ b/configure.ac
@@ -96,6 +96,18 @@ AC_PATH_ZLIB
 
 AC_SYS_LARGEFILE
 
+
+dnl ----------------------------------------------------------------------------
+dnl
+dnl posix_fadvise
+
+dnl can posix_fadvise be used
+AC_CHECK_DECLS(posix_fadvise, [], [], [
+#define _XOPEN_SOURCE 600
+#include <fcntl.h>])
+AC_CHECK_FUNCS([posix_fadvise])
+
+
 dnl ----------------------------------------------------------------------------
 dnl
 dnl va_copy
diff --git a/libtransmission/fdlimit.c b/libtransmission/fdlimit.c
index b21eb7737..746ac6864 100644
--- a/libtransmission/fdlimit.c
+++ b/libtransmission/fdlimit.c
@@ -231,6 +231,9 @@ TrOpenFile( int                      i,
     
     /* open the file */
     flags = doWrite ? ( O_RDWR | O_CREAT ) : O_RDONLY;
+#ifdef O_RANDOM
+    flags |= O_RANDOM
+#endif
 #ifdef O_LARGEFILE
     flags |= O_LARGEFILE;
 #endif
@@ -249,6 +252,13 @@ TrOpenFile( int                      i,
     if( doWrite && !alreadyExisted && ( preallocationMode == TR_PREALLOCATE_SPARSE ) )
         preallocateFileSparse( file->fd, desiredFileSize );
 
+#if defined( SYS_DARWIN )
+    fcntl( file->fd, F_NOCACHE, 1 );
+    fcntl( file->fd, F_RDAHEAD, 0 );
+#elif defined( HAVE_POSIX_FADVISE )
+    posix_fadvise( file->fd, 0, 0, POSIX_FADV_RANDOM );
+#endif
+
     tr_free( filename );
     return 0;
 }