Use strbuf for struct xdiff_emit_state's remainder

Continually xreallocing and freeing the remainder member of struct
xdiff_emit_state was a noticeable performance hit.  Use a strbuf
instead.

This yields a decent performance improvement on "git blame" on certain
repositories.  For example, before this commit:

$ time git blame -M -C -C -p --incremental server.c >/dev/null
101.52user 0.17system 1:41.73elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+39561minor)pagefaults 0swaps

With this commit:

$ time git blame -M -C -C -p --incremental server.c >/dev/null
80.38user 0.30system 1:20.81elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+50979minor)pagefaults 0swaps

Signed-off-by: Brian Downing <bdowning@lavos.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/xdiff-interface.c b/xdiff-interface.c
index 828b4966a9d1e692ec7a8225406c78fca15bb5d0..bf98866c4f5aa2027135741cb07bc1ec04b11e9f 100644 (file)
--- a/xdiff-interface.c
+++ b/xdiff-interface.c
@@ -69,36 +69,22 @@ static int xdiff_outf(void *priv_, mmbuffer_t *mb, int nbuf)
        for (i = 0; i < nbuf; i++) {
                if (mb[i].ptr[mb[i].size-1] != '\n') {
                        /* Incomplete line */
-                       priv->remainder = xrealloc(priv->remainder,
-                                                  priv->remainder_size +
-                                                  mb[i].size);
-                       memcpy(priv->remainder + priv->remainder_size,
-                              mb[i].ptr, mb[i].size);
-                       priv->remainder_size += mb[i].size;
+                       strbuf_add(&priv->remainder, mb[i].ptr, mb[i].size);
                        continue;
                }
 
                /* we have a complete line */
-               if (!priv->remainder) {
+               if (!priv->remainder.len) {
                        consume_one(priv, mb[i].ptr, mb[i].size);
                        continue;
                }
-               priv->remainder = xrealloc(priv->remainder,
-                                          priv->remainder_size +
-                                          mb[i].size);
-               memcpy(priv->remainder + priv->remainder_size,
-                      mb[i].ptr, mb[i].size);
-               consume_one(priv, priv->remainder,
-                           priv->remainder_size + mb[i].size);
-               free(priv->remainder);
-               priv->remainder = NULL;
-               priv->remainder_size = 0;
+               strbuf_add(&priv->remainder, mb[i].ptr, mb[i].size);
+               consume_one(priv, priv->remainder.buf, priv->remainder.len);
+               strbuf_reset(&priv->remainder);
        }
-       if (priv->remainder) {
-               consume_one(priv, priv->remainder, priv->remainder_size);
-               free(priv->remainder);
-               priv->remainder = NULL;
-               priv->remainder_size = 0;
+       if (priv->remainder.len) {
+               consume_one(priv, priv->remainder.buf, priv->remainder.len);
+               strbuf_reset(&priv->remainder);
        }
        return 0;
 }
@@ -148,7 +134,9 @@ int xdi_diff_outf(mmfile_t *mf1, mmfile_t *mf2,
        int ret;
        xecb->outf = xdiff_outf;
        xecb->priv = state;
+       strbuf_init(&state->remainder, 0);
        ret = xdi_diff(mf1, mf2, xpp, xecfg, xecb);
+       strbuf_release(&state->remainder);
        return ret;
 }
 

diff --git a/xdiff-interface.h b/xdiff-interface.h
index 6f3b361a845f0f71ece8188e00a3cfa12138edd4..f6a1ec2220512b9aff5c69c4a7f94b0af0dbe3e2 100644 (file)
--- a/xdiff-interface.h
+++ b/xdiff-interface.h
@@ -2,6 +2,7 @@
 #define XDIFF_INTERFACE_H
 
 #include "xdiff/xdiff.h"
+#include "strbuf.h"
 
 struct xdiff_emit_state;
 
@@ -9,8 +10,7 @@ typedef void (*xdiff_emit_consume_fn)(void *, char *, unsigned long);
 
 struct xdiff_emit_state {
        xdiff_emit_consume_fn consume;
-       char *remainder;
-       unsigned long remainder_size;
+       struct strbuf remainder;
 };
 
 int xdi_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp, xdemitconf_t const *xecfg, xdemitcb_t *ecb);