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authorBartosz Golaszewski2014-11-27 13:20:24 +0100
committerDenys Vlasenko2014-11-27 23:31:58 +0100
commit8d75d794ea505003fddea8e757d43976db8d6861 (patch)
tree0aae42250953ae1de36666aa5fc12a11ad3be02f /libbb
parentee41094b809452fdd23d25c1879a96acfcddde08 (diff)
downloadbusybox-8d75d794ea505003fddea8e757d43976db8d6861.zip
busybox-8d75d794ea505003fddea8e757d43976db8d6861.tar.gz
libbb: use sendfile() to copy data between file descriptors
Busybox already uses sendfile in httpd. This patch proposes to use it globally to copy data between file descriptors. It speeds up the copying on slow systems a lot - below are the times needed to copy a 450Mb file with and without this option enabled on a BeagleBone Black: sendfile: user 0m0.000s sys 0m8.170s read/write 4k: user 0m0.470s sys 0m16.300s function old new delta bb_full_fd_action 394 474 +80 Signed-off-by: Bartosz Golaszewski <bartekgola@gmail.com> Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
Diffstat (limited to 'libbb')
-rw-r--r--libbb/copyfd.c87
1 files changed, 56 insertions, 31 deletions
diff --git a/libbb/copyfd.c b/libbb/copyfd.c
index eda2747..7e35319 100644
--- a/libbb/copyfd.c
+++ b/libbb/copyfd.c
@@ -8,6 +8,20 @@
*/
#include "libbb.h"
+#if ENABLE_FEATURE_USE_SENDFILE
+# include <sys/sendfile.h>
+#else
+# define sendfile(a,b,c,d) (-1)
+#endif
+
+/*
+ * We were using 0x7fff0000 as sendfile chunk size, but it
+ * was seen to cause largish delays when user tries to ^C a file copy.
+ * Let's use a saner size.
+ * Note: needs to be >= max(CONFIG_FEATURE_COPYBUF_KB),
+ * or else "copy to eof" code will use neddlesly short reads.
+ */
+#define SENDFILE_BIGBUF (16*1024*1024)
/* Used by NOFORK applets (e.g. cat) - must not use xmalloc.
* size < 0 means "ignore write errors", used by tar --to-command
@@ -18,12 +32,13 @@ static off_t bb_full_fd_action(int src_fd, int dst_fd, off_t size)
int status = -1;
off_t total = 0;
bool continue_on_write_error = 0;
-#if CONFIG_FEATURE_COPYBUF_KB <= 4
+ ssize_t sendfile_sz;
+#if CONFIG_FEATURE_COPYBUF_KB > 4
+ char *buffer = buffer; /* for compiler */
+ int buffer_size = 0;
+#else
char buffer[CONFIG_FEATURE_COPYBUF_KB * 1024];
enum { buffer_size = sizeof(buffer) };
-#else
- char *buffer;
- int buffer_size;
#endif
if (size < 0) {
@@ -31,46 +46,58 @@ static off_t bb_full_fd_action(int src_fd, int dst_fd, off_t size)
continue_on_write_error = 1;
}
-#if CONFIG_FEATURE_COPYBUF_KB > 4
- if (size > 0 && size <= 4 * 1024)
- goto use_small_buf;
- /* We want page-aligned buffer, just in case kernel is clever
- * and can do page-aligned io more efficiently */
- buffer = mmap(NULL, CONFIG_FEATURE_COPYBUF_KB * 1024,
- PROT_READ | PROT_WRITE,
- MAP_PRIVATE | MAP_ANON,
- /* ignored: */ -1, 0);
- buffer_size = CONFIG_FEATURE_COPYBUF_KB * 1024;
- if (buffer == MAP_FAILED) {
- use_small_buf:
- buffer = alloca(4 * 1024);
- buffer_size = 4 * 1024;
- }
-#endif
-
if (src_fd < 0)
goto out;
+ sendfile_sz = !ENABLE_FEATURE_USE_SENDFILE
+ ? 0
+ : SENDFILE_BIGBUF;
if (!size) {
- size = buffer_size;
+ size = SENDFILE_BIGBUF;
status = 1; /* copy until eof */
}
while (1) {
ssize_t rd;
- rd = safe_read(src_fd, buffer, size > buffer_size ? buffer_size : size);
-
- if (!rd) { /* eof - all done */
- status = 0;
- break;
+ if (sendfile_sz) {
+ rd = sendfile(dst_fd, src_fd, NULL,
+ size > sendfile_sz ? sendfile_sz : size);
+ if (rd >= 0)
+ goto read_ok;
+ sendfile_sz = 0; /* do not try sendfile anymore */
+ }
+#if CONFIG_FEATURE_COPYBUF_KB > 4
+ if (buffer_size == 0) {
+ if (size > 0 && size <= 4 * 1024)
+ goto use_small_buf;
+ /* We want page-aligned buffer, just in case kernel is clever
+ * and can do page-aligned io more efficiently */
+ buffer = mmap(NULL, CONFIG_FEATURE_COPYBUF_KB * 1024,
+ PROT_READ | PROT_WRITE,
+ MAP_PRIVATE | MAP_ANON,
+ /* ignored: */ -1, 0);
+ buffer_size = CONFIG_FEATURE_COPYBUF_KB * 1024;
+ if (buffer == MAP_FAILED) {
+ use_small_buf:
+ buffer = alloca(4 * 1024);
+ buffer_size = 4 * 1024;
+ }
}
+#endif
+ rd = safe_read(src_fd, buffer,
+ size > buffer_size ? buffer_size : size);
if (rd < 0) {
bb_perror_msg(bb_msg_read_error);
break;
}
+ read_ok:
+ if (!rd) { /* eof - all done */
+ status = 0;
+ break;
+ }
/* dst_fd == -1 is a fake, else... */
- if (dst_fd >= 0) {
+ if (dst_fd >= 0 && !sendfile_sz) {
ssize_t wr = full_write(dst_fd, buffer, rd);
if (wr < rd) {
if (!continue_on_write_error) {
@@ -92,10 +119,8 @@ static off_t bb_full_fd_action(int src_fd, int dst_fd, off_t size)
}
out:
-#if CONFIG_FEATURE_COPYBUF_KB > 4
- if (buffer_size != 4 * 1024)
+ if (buffer_size > 4 * 1024)
munmap(buffer, buffer_size);
-#endif
return status ? -1 : total;
}