Reduce bss usage and speed up string printing

   text	   data	    bss	    dec	    hex	filename
 237913	    660	  49284	 287857	  46471	strace.before
 237973	    660	  28772	 267405	  4148d	strace

This reduces L1 D-cache pressure a bit: instead of dirtying
20k of bss, we will reuse already dirty stack area.

* util.c (printpathn): Use on-stack buffers instead of static ones.
Saves 5*MAXPATHLEN in bss.
(printstr): Use tprints() instead of tprintf("%s") when printing
formatted string. May be a bit faster, depending on libc.

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>

diff --git a/util.c b/util.c
index 0283a9eea4a9b1898b992c42a911637148426868..2c21b4939a6ec61d61241e62df5da776096c13e6 100644 (file)
--- a/util.c
+++ b/util.c
@@ -427,8 +427,6 @@ printuid(const char *text, unsigned long uid)
        tprintf((uid == -1) ? "%s%ld" : "%s%lu", text, uid);
 }
 
-static char path[MAXPATHLEN + 1];
-
 /*
  * Quote string `instr' of length `size'
  * Write up to (3 + `size' * 4) bytes to `outstr' buffer.
@@ -566,6 +564,8 @@ string_quote(const char *instr, char *outstr, int len, int size)
 void
 printpathn(struct tcb *tcp, long addr, int n)
 {
+       char path[MAXPATHLEN + 1];
+
        if (!addr) {
                tprints("NULL");
                return;
@@ -581,24 +581,25 @@ printpathn(struct tcb *tcp, long addr, int n)
        if (umovestr(tcp, addr, n + 1, path) < 0)
                tprintf("%#lx", addr);
        else {
-               static char outstr[4*(sizeof path - 1) + sizeof "\"...\""];
-               const char *fmt;
+               char *outstr;
                int trunc = (path[n] != '\0');
 
                if (trunc)
                        path[n] = '\0';
-               string_quote(path, outstr, -1, n + 1);
-               fmt = "%s";
+               n++;
+               outstr = alloca(4 * n); /* 4*(n-1) + 2 for quotes */
+               string_quote(path, outstr, -1, n);
+               tprints(outstr);
                if (trunc)
-                       fmt = "%s...";
-               tprintf(fmt, outstr);
+                       tprints("...");
        }
 }
 
 void
 printpath(struct tcb *tcp, long addr)
 {
-       printpathn(tcp, addr, sizeof path - 1);
+       /* Size must correspond to char path[] size in printpathn */
+       printpathn(tcp, addr, MAXPATHLEN);
 }
 
 /*
@@ -612,7 +613,7 @@ printstr(struct tcb *tcp, long addr, int len)
        static char *str = NULL;
        static char *outstr;
        int size;
-       const char *fmt;
+       int ellipsis;
 
        if (!addr) {
                tprints("NULL");
@@ -623,9 +624,7 @@ printstr(struct tcb *tcp, long addr, int len)
                str = malloc(max_strlen + 1);
                if (!str)
                        die_out_of_memory();
-       }
-       if (!outstr) {
-               outstr = malloc(4 * max_strlen + sizeof "\"...\"");
+               outstr = malloc(4 * max_strlen + /*for quotes:*/ 2);
                if (!outstr)
                        die_out_of_memory();
        }
@@ -651,12 +650,12 @@ printstr(struct tcb *tcp, long addr, int len)
                }
        }
 
-       fmt = "%s";
-       if (string_quote(str, outstr, len, size) &&
-           (len < 0 || len > max_strlen))
-               fmt = "%s...";
+       ellipsis = (string_quote(str, outstr, len, size) &&
+                       (len < 0 || len > max_strlen));
 
-       tprintf(fmt, outstr);
+       tprints(outstr);
+       if (ellipsis)
+               tprints("...");
 }
 
 #if HAVE_SYS_UIO_H