Module Name: src
Committed By: tron
Date: Mon Oct 25 08:19:47 UTC 2010
Modified Files:
src/bin/cp: utils.c
Log Message:
Re-enable support for reading files smaller of at most 8MB via mmap(2).
Write out the mmap-ed data in small chunks to avoid locking the output
file for a long time.
Suggested by David Holland on "source-changes-d" mailing list.
To generate a diff of this commit:
cvs rdiff -u -r1.35 -r1.36 src/bin/cp/utils.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/bin/cp/utils.c
diff -u src/bin/cp/utils.c:1.35 src/bin/cp/utils.c:1.36
--- src/bin/cp/utils.c:1.35 Fri Oct 22 17:56:06 2010
+++ src/bin/cp/utils.c Mon Oct 25 08:19:47 2010
@@ -1,4 +1,4 @@
-/* $NetBSD: utils.c,v 1.35 2010/10/22 17:56:06 pooka Exp $ */
+/* $NetBSD: utils.c,v 1.36 2010/10/25 08:19:47 tron Exp $ */
/*-
* Copyright (c) 1991, 1993, 1994
@@ -34,7 +34,7 @@
#if 0
static char sccsid[] = "@(#)utils.c 8.3 (Berkeley) 4/1/94";
#else
-__RCSID("$NetBSD: utils.c,v 1.35 2010/10/22 17:56:06 pooka Exp $");
+__RCSID("$NetBSD: utils.c,v 1.36 2010/10/25 08:19:47 tron Exp $");
#endif
#endif /* not lint */
@@ -47,6 +47,7 @@
#include <errno.h>
#include <fcntl.h>
#include <fts.h>
+#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
@@ -54,6 +55,9 @@
#include "extern.h"
+#define MMAP_MAX_SIZE (8 * 1048576)
+#define MMAP_MAX_WRITE (64 * 1024)
+
int
set_utimes(const char *file, struct stat *fs)
{
@@ -75,6 +79,7 @@
static char buf[MAXBSIZE];
struct stat to_stat, *fs;
int ch, checkch, from_fd, rcount, rval, to_fd, tolnk, wcount;
+ char *p;
if ((from_fd = open(entp->fts_path, O_RDONLY, 0)) == -1) {
warn("%s", entp->fts_path);
@@ -145,47 +150,55 @@
*/
if (fs->st_size > 0) {
-
- /*
- * Disable use of mmap. With the current vnode locking
- * scheme it has a very annoying property: if the source
- * media is slow (like a slow network), the target file
- * will be locked for the duration of the entire max 8MB
- * write and cause processes attempting to e.g. stat() it
- * to "tstile". Revisit when vnode locking gets a little
- * smarter.
- */
-#ifdef VNODE_LOCKING_IS_SMARTER_NOW
/*
* Mmap and write if less than 8M (the limit is so
* we don't totally trash memory on big files).
* This is really a minor hack, but it wins some CPU back.
*/
+ bool use_read;
- if (fs->st_size <= 8 * 1048576) {
+ use_read = true;
+ if (fs->st_size <= MMAP_MAX_SIZE) {
size_t fsize = (size_t)fs->st_size;
- char *p;
-
p = mmap(NULL, fsize, PROT_READ, MAP_FILE|MAP_SHARED,
from_fd, (off_t)0);
- if (p == MAP_FAILED) {
- goto mmap_failed;
- } else {
+ if (p != MAP_FAILED) {
+ size_t remainder;
+
+ use_read = false;
+
(void) madvise(p, (size_t)fs->st_size,
MADV_SEQUENTIAL);
- if (write(to_fd, p, fsize) !=
- fs->st_size) {
- warn("%s", to.p_path);
- rval = 1;
- }
+
+ /*
+ * Write out the data in small chunks to
+ * avoid locking the output file for a
+ * long time if the reading the data from
+ * the source is slow.
+ */
+ remainder = fsize;
+ do {
+ ssize_t chunk;
+
+ chunk = (remainder > MMAP_MAX_WRITE) ?
+ MMAP_MAX_WRITE : remainder;
+ if (write(to_fd, &p[fsize - remainder],
+ chunk) != chunk) {
+ warn("%s", to.p_path);
+ rval = 1;
+ break;
+ }
+ remainder -= chunk;
+ } while (remainder > 0);
+
if (munmap(p, fsize) < 0) {
warn("%s", entp->fts_path);
rval = 1;
}
}
- } else {
-mmap_failed:
-#endif
+ }
+
+ if (use_read) {
while ((rcount = read(from_fd, buf, MAXBSIZE)) > 0) {
wcount = write(to_fd, buf, (size_t)rcount);
if (rcount != wcount || wcount == -1) {
@@ -198,9 +211,7 @@
warn("%s", entp->fts_path);
rval = 1;
}
-#ifdef VNODE_LOCKING_IS_SMARTER_NOW
}
-#endif
}
if (rval == 1) {
