tee(1): increase I/O buffer size from 8KB to 64KB

64KB strikes a good balance between space and time on today's
machines.  Buffers smaller than 64KB waste more time in userspace
traveling to and from the kernel.  Buffers larger than 64KB do I/O a
bit faster, but the performance improvements rapidly diminish at a
steep memory cost.

Discussed with millert@ and deraadt@.  Positive feedback from Geoff
Steckel.

Thread: https://marc.info/?l=openbsd-tech&m=163737586414354&w=2

ok millert@ deraadt@

diff --git a/usr.bin/tee/tee.c b/usr.bin/tee/tee.c
index 826aeaa..0ead177 100644 (file)
--- a/usr.bin/tee/tee.c
+++ b/usr.bin/tee/tee.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: tee.c,v 1.13 2021/11/21 16:15:43 cheloha Exp $        */
+/*     $OpenBSD: tee.c,v 1.14 2021/12/13 18:33:23 cheloha Exp $        */
 /*     $NetBSD: tee.c,v 1.5 1994/12/09 01:43:39 jtc Exp $      */
 
 /*
@@ -43,6 +43,8 @@
 #include <string.h>
 #include <unistd.h>
 
+#define BSIZE (64 * 1024)
+
 struct list {
        SLIST_ENTRY(list) next;
        int fd;
@@ -69,7 +71,7 @@ main(int argc, char *argv[])
        int fd;
        ssize_t n, rval, wval;
        int append, ch, exitval;
-       char buf[8192];
+       char *buf;
 
        if (pledge("stdio wpath cpath", NULL) == -1)
                err(1, "pledge");
@@ -109,7 +111,10 @@ main(int argc, char *argv[])
        if (pledge("stdio", NULL) == -1)
                err(1, "pledge");
 
-       while ((rval = read(STDIN_FILENO, buf, sizeof(buf))) > 0) {
+       buf = malloc(BSIZE);
+       if (buf == NULL)
+               err(1, NULL);
+       while ((rval = read(STDIN_FILENO, buf, BSIZE)) > 0) {
                SLIST_FOREACH(p, &head, next) {
                        for (n = 0; n < rval; n += wval) {
                                wval = write(p->fd, buf + n, rval - n);
@@ -121,6 +126,7 @@ main(int argc, char *argv[])
                        }
                }
        }
+       free(buf);
        if (rval == -1) {
                warn("read");
                exitval = 1;