svn commit: r184471 - in head/bin: cat cp
Ivan Voras
ivoras at FreeBSD.org
Thu Oct 30 07:05:58 PDT 2008
Author: ivoras
Date: Thu Oct 30 14:05:57 2008
New Revision: 184471
URL: http://svn.freebsd.org/changeset/base/184471
Log:
Teach cat(1) and cp(1) to use a larger buffer if enough memory is present
in the system. A simple heuristics is used to detect what is "enough"
memory: if number of physmem pages is greater than 32k (equalling 128 MB
on machines with 4 kB pages).
Typical immediate result of these changes is reduction in context switches
and the goal is to increase efficiency by using large buffers:
before: /usr/bin/time -hlp cat file1 > file2
...
163 voluntary context switches
11194 involuntary context switches
after: /usr/bin/time -hlp ./cat file1 > file2
...
417 voluntary context switches
272 involuntary context switches
Reviewed by: hackers@ (no objections to earlier version of cat patch)
Approved by: gnn (mentor)
MFC after: 4 months
Modified:
head/bin/cat/cat.c
head/bin/cp/utils.c
Modified: head/bin/cat/cat.c
==============================================================================
--- head/bin/cat/cat.c Thu Oct 30 13:18:28 2008 (r184470)
+++ head/bin/cat/cat.c Thu Oct 30 14:05:57 2008 (r184471)
@@ -77,6 +77,17 @@ static void raw_cat(int);
static int udom_open(const char *path, int flags);
#endif
+/* Memory strategy threshold, in pages: if physmem is larger then this, use a
+ * large buffer */
+#define PHYSPAGES_THRESHOLD (32*1024)
+
+/* Maximum buffer size in bytes - do not allow it to grow larger than this */
+#define BUFSIZE_MAX (2*1024*1024)
+
+/* Small (default) buffer size in bytes. It's inefficient for this to be
+ * smaller than MAXPHYS */
+#define BUFSIZE_SMALL (MAXPHYS)
+
int
main(int argc, char *argv[])
{
@@ -247,9 +258,17 @@ raw_cat(int rfd)
if (buf == NULL) {
if (fstat(wfd, &sbuf))
err(1, "%s", filename);
- bsize = MAX(sbuf.st_blksize, 1024);
+ if (S_ISREG(sbuf.st_mode)) {
+ /* If there's plenty of RAM, use a large copy buffer */
+ if (sysconf(_SC_PHYS_PAGES) > PHYSPAGES_THRESHOLD)
+ bsize = MIN(BUFSIZE_MAX, MAXPHYS*8);
+ else
+ bsize = BUFSIZE_SMALL;
+ } else
+ bsize = MAX(sbuf.st_blksize,
+ (blksize_t)sysconf(_SC_PAGESIZE));
if ((buf = malloc(bsize)) == NULL)
- err(1, "buffer");
+ err(1, "malloc() failure of IO buffer");
}
while ((nr = read(rfd, buf, bsize)) > 0)
for (off = 0; nr; nr -= nw, off += nw)
Modified: head/bin/cp/utils.c
==============================================================================
--- head/bin/cp/utils.c Thu Oct 30 13:18:28 2008 (r184470)
+++ head/bin/cp/utils.c Thu Oct 30 14:05:57 2008 (r184471)
@@ -57,10 +57,22 @@ __FBSDID("$FreeBSD$");
#define cp_pct(x, y) ((y == 0) ? 0 : (int)(100.0 * (x) / (y)))
+/* Memory strategy threshold, in pages: if physmem is larger then this, use a
+ * large buffer */
+#define PHYSPAGES_THRESHOLD (32*1024)
+
+/* Maximum buffer size in bytes - do not allow it to grow larger than this */
+#define BUFSIZE_MAX (2*1024*1024)
+
+/* Small (default) buffer size in bytes. It's inefficient for this to be
+ * smaller than MAXPHYS */
+#define BUFSIZE_SMALL (MAXPHYS)
+
int
copy_file(const FTSENT *entp, int dne)
{
- static char buf[MAXBSIZE];
+ static char *buf = NULL;
+ static size_t bufsize;
struct stat *fs;
ssize_t wcount;
size_t wresid;
@@ -174,8 +186,23 @@ copy_file(const FTSENT *entp, int dne)
} else
#endif
{
+ if (buf == NULL) {
+ /*
+ * Note that buf and bufsize are static. If
+ * malloc() fails, it will fail at the start
+ * and not copy only some files.
+ */
+ if (sysconf(_SC_PHYS_PAGES) >
+ PHYSPAGES_THRESHOLD)
+ bufsize = MIN(BUFSIZE_MAX, MAXPHYS * 8);
+ else
+ bufsize = BUFSIZE_SMALL;
+ buf = malloc(bufsize);
+ if (buf == NULL)
+ err(1, "Not enough memory");
+ }
wtotal = 0;
- while ((rcount = read(from_fd, buf, MAXBSIZE)) > 0) {
+ while ((rcount = read(from_fd, buf, bufsize)) > 0) {
for (bufp = buf, wresid = rcount; ;
bufp += wcount, wresid -= wcount) {
wcount = write(to_fd, bufp, wresid);
More information about the svn-src-head
mailing list