On 08/04/2007, at 5:23 PM, Jeremy Allison wrote:
On Sun, Apr 08, 2007 at 05:09:36PM -0700, James Peach wrote:
You could add this to vfs_cacheprime, and just have an option that
determines whether it does a readahead (ie. I/O hint) or an actual
read(2).
I await your patch :-).
I knew you were going to say that!
Sure, but 2 modules that do *almost* the same thing is just
confusing.
I don't think they do. readahead is built around
this one syscall on Linux. It's not the same as
cacheprime - cacheprime reads from the start of
the file, readahead triggers on every pread/sendfile
request that matches offset MOD readahead_offset.
They're not *exactly* the same, but they are mostly the same. The
difference is quite subtle. This patch should resolve the differences:
Index: SAMBA_3_0/source/modules/vfs_cacheprime.c
===================================================================
--- SAMBA_3_0/source/modules/vfs_cacheprime.c (revision 22132)
+++ SAMBA_3_0/source/modules/vfs_cacheprime.c (working copy)
@@ -1,5 +1,6 @@
/*
- * Copyright (c) James Peach 2005-2006
+ * Copyright (c) James Peach 2005-2007
+ * Copyright (c) Jeremy Allison 2007
*
* This program is free software; you can redistribute it and/or
modify
* it under the terms of the GNU General Public License as
published by
@@ -31,6 +32,14 @@
* cacheprime:rsize Amount of readahead in bytes. This
should be a
* multiple of the RAID stripe width.
* cacheprime:debug Debug level at which to emit messages.
+ * cacheprime:force alignment
+ * Force all I/O to be aligned to an rsize
boundary.
+ * If this is false, we simply issue a
readahead on
+ * each rsize boundary.
+ *
+ * To configure for Vista:
+ * cacheprime:rsize = 0x80000
+ * cacheprime:force alignment = no
*/
#define READAHEAD_MIN (128 * 1024) /* min is 128 KiB */
@@ -41,7 +50,38 @@
static int module_debug;
static ssize_t g_readsz = 0;
static void * g_readbuf = NULL;
+static BOOL g_forcealign = False;
+static void sys_readahead(int fd, SMB_OFF_T offset, SMB_OFF_T len)
+{
+ static BOOL didmsg = False;
+ int err;
+
+#if defined(HAVE_LINUX_READAHEAD)
+ err = readahead(fromfd, offset, (size_t)rhd->len);
+
+ DEBUG(10,("%s: readahead on fd %u, offset %llu, len %u returned %d
\n",
+ MODULE,
+ (unsigned int)fromfd,
+ (unsigned long long)offset,
+ (unsigned int)rhd->len,
+ err ));
+#elif defined(HAVE_POSIX_FADVISE)
+ err = posix_fadvise(fromfd, offset, (off_t)rhd->len,
POSIX_FADV_WILLNEED);
+ DEBUG(10,("%s: posix_fadvise on fd %u, offset %llu, len %u
returned %d\n",
+ MODULE,
+ (unsigned int)fromfd,
+ (unsigned long long)offset,
+ (unsigned int)rhd->len,
+ err ));
+#else
+ if (!didmsg) {
+ DEBUG(0,("%s: no readahead on this platform\n",
MODULE));
+ didmsg = True;
+ }
+#endif
+}
+
/* Prime the kernel buffer cache with data from the specified file.
We use
* per-fsp data to make sure we only ever do this once. If pread is
being
* emulated by seek/read/seek, when this will suck quite a lot.
@@ -71,15 +111,20 @@
return False;
}
- DEBUG(module_debug,
- ("%s: doing readahead of %lld bytes at %lld for %s\n",
- MODULE, (long long)g_readsz, (long long)*last,
- fsp->fsp_name));
+ if (g_forcealign) {
+ DEBUG(module_debug,
+ ("%s: doing readahead of %lld bytes at %lld for %
s\n",
+ MODULE, (long long)g_readsz, (long long)*last,
+ fsp->fsp_name));
- nread = sys_pread(fd, g_readbuf, g_readsz, *last);
- if (nread < 0) {
- *last = -1;
- return False;
+ nread = sys_pread(fd, g_readbuf, g_readsz, *last);
+ if (nread < 0) {
+ *last = -1;
+ return False;
+ }
+ } else {
+ sys_readahead(fd, *last, g_readsz);
+ nread += g_readsz;
}
*last += nread;
@@ -103,6 +148,9 @@
g_readsz = conv_str_size(lp_parm_const_string(SNUM(handle-
>conn),
MODULE, "rsize", NULL));
+ g_forcealign = lp_parm_bool(SNUM(handle->conn), MODULE,
+ "force alignment", False);
+
if (g_readsz < READAHEAD_MIN) {
DEBUG(module_debug, ("%s: %ld bytes of readahead "
"requested, using minimum of %u\n",
@@ -115,9 +163,11 @@
g_readsz = READAHEAD_MAX;
}
- if ((g_readbuf = SMB_MALLOC(g_readsz)) == NULL) {
- /* Turn off readahead if we can't get a buffer. */
- g_readsz = 0;
+ if (g_forcealign == True) {
+ if ((g_readbuf = SMB_MALLOC(g_readsz)) == NULL) {
+ /* Turn off readahead if we can't get a
buffer. */
+ g_readsz = 0;
+ }
}
return SMB_VFS_NEXT_CONNECT(handle, service, user);
--
James Peach | [EMAIL PROTECTED]
