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authorBartosz Golaszewski <bartekgola@gmail.com>2014-11-27 12:20:24 (GMT)
committer Denys Vlasenko <vda.linux@googlemail.com>2014-11-27 22:31:58 (GMT)
commit8d75d794ea505003fddea8e757d43976db8d6861 (patch)
tree0aae42250953ae1de36666aa5fc12a11ad3be02f
parentee41094b809452fdd23d25c1879a96acfcddde08 (diff)
downloadbusybox-master.tar.gz
busybox-master.tar.bz2
libbb: use sendfile() to copy data between file descriptorsHEADmaster
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>
-rw-r--r--Config.in12
-rw-r--r--libbb/copyfd.c87
-rw-r--r--networking/Config.src8
-rw-r--r--networking/httpd.c6
4 files changed, 71 insertions, 42 deletions
diff --git a/Config.in b/Config.in
index b83beb5..285fe0a 100644
--- a/Config.in
+++ b/Config.in
@@ -264,6 +264,18 @@ config PAM
Use PAM in some busybox applets (currently login and httpd) instead
of direct access to password database.
+config FEATURE_USE_SENDFILE
+ bool "Use sendfile system call"
+ default y
+ help
+ When enabled, busybox will use the kernel sendfile() function
+ instead of read/write loops to copy data between file descriptors
+ (for example, cp command does this a lot).
+ If sendfile() doesn't work, copying code falls back to read/write
+ loop. sendfile() was originally implemented for faster I/O
+ from files to sockets, but since Linux 2.6.33 it was extended
+ to work for many more file types.
+
config LONG_OPTS
bool "Support for --long-options"
default y
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;
}
diff --git a/networking/Config.src b/networking/Config.src
index e566469..15a6968 100644
--- a/networking/Config.src
+++ b/networking/Config.src
@@ -181,14 +181,6 @@ config FEATURE_HTTPD_RANGES
"Range: bytes=NNN-[MMM]" header. Allows for resuming interrupted
downloads, seeking in multimedia players etc.
-config FEATURE_HTTPD_USE_SENDFILE
- bool "Use sendfile system call"
- default y
- depends on HTTPD
- help
- When enabled, httpd will use the kernel sendfile() function
- instead of read/write loop.
-
config FEATURE_HTTPD_SETUID
bool "Enable -u <user> option"
default y
diff --git a/networking/httpd.c b/networking/httpd.c
index 621d9cd..9cf0804 100644
--- a/networking/httpd.c
+++ b/networking/httpd.c
@@ -133,7 +133,7 @@
# include <security/pam_appl.h>
# include <security/pam_misc.h>
#endif
-#if ENABLE_FEATURE_HTTPD_USE_SENDFILE
+#if ENABLE_FEATURE_USE_SENDFILE
# include <sys/sendfile.h>
#endif
/* amount of buffering in a pipe */
@@ -1624,7 +1624,7 @@ static NOINLINE void send_file_and_exit(const char *url, int what)
#endif
if (what & SEND_HEADERS)
send_headers(HTTP_OK);
-#if ENABLE_FEATURE_HTTPD_USE_SENDFILE
+#if ENABLE_FEATURE_USE_SENDFILE
{
off_t offset = range_start;
while (1) {
@@ -1654,7 +1654,7 @@ static NOINLINE void send_file_and_exit(const char *url, int what)
break;
}
if (count < 0) {
- IF_FEATURE_HTTPD_USE_SENDFILE(fin:)
+ IF_FEATURE_USE_SENDFILE(fin:)
if (verbose > 1)
bb_perror_msg("error");
}