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Re-enable support for reading files 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.
This commit is contained in:
tron 2010-10-25 08:19:47 +00:00
parent 70e14dc983
commit 1181f40421
1 changed files with 40 additions and 29 deletions
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69
bin/cp/utils.c
View File

@ -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 $");
#endif
#endif /* not lint */
@ -47,6 +47,7 @@ __RCSID("$NetBSD: utils.c,v 1.35 2010/10/22 17:56:06 pooka Exp $");
#include <errno.h>
#include <fcntl.h>
#include <fts.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
@ -54,6 +55,9 @@ __RCSID("$NetBSD: utils.c,v 1.35 2010/10/22 17:56:06 pooka Exp $");
#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 @@ copy_file(FTSENT *entp, int dne)
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 @@ copy_file(FTSENT *entp, int dne)
*/
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 @@ mmap_failed:
warn("%s", entp->fts_path);
rval = 1;
}
#ifdef VNODE_LOCKING_IS_SMARTER_NOW
}
#endif
}
if (rval == 1) {