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fixup_pack_header_footer(): use nicely aligned buffer sizes 

It should be more efficient to use nicely aligned buffer sizes, either
for filesystem operations or SHA1 checksums.  Also, using a relatively
small nominal size might allow for the data to remain in L1 cache
between both SHA1_Update() calls.

Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
maint
Nicolas Pitre 2008-08-29 16:08:02 -04:00 committed by Junio C Hamano
parent 8522148f79
commit d35825da6d
1 changed files with 8 additions and 3 deletions
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11
pack-write.c
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@ -167,7 +167,7 @@ void fixup_pack_header_footer(int pack_fd,
unsigned char *partial_pack_sha1, unsigned char *partial_pack_sha1,
off_t partial_pack_offset) off_t partial_pack_offset)
{ {
static const int buf_sz = 128 * 1024; int aligned_sz, buf_sz = 8 * 1024;
SHA_CTX old_sha1_ctx, new_sha1_ctx; SHA_CTX old_sha1_ctx, new_sha1_ctx;
struct pack_header hdr; struct pack_header hdr;
char *buf; char *buf;
@ -188,10 +188,11 @@ void fixup_pack_header_footer(int pack_fd,
partial_pack_offset -= sizeof(hdr); partial_pack_offset -= sizeof(hdr);


buf = xmalloc(buf_sz); buf = xmalloc(buf_sz);
aligned_sz = buf_sz - sizeof(hdr);
for (;;) { for (;;) {
ssize_t m, n; ssize_t m, n;
m = (partial_pack_sha1 && partial_pack_offset < buf_sz) ? m = (partial_pack_sha1 && partial_pack_offset < aligned_sz) ?
partial_pack_offset : buf_sz; partial_pack_offset : aligned_sz;
n = xread(pack_fd, buf, m); n = xread(pack_fd, buf, m);
if (!n) if (!n)
break; break;
@ -199,6 +200,10 @@ void fixup_pack_header_footer(int pack_fd,
die("Failed to checksum %s: %s", pack_name, strerror(errno)); die("Failed to checksum %s: %s", pack_name, strerror(errno));
SHA1_Update(&new_sha1_ctx, buf, n); SHA1_Update(&new_sha1_ctx, buf, n);


aligned_sz -= n;
if (!aligned_sz)
aligned_sz = buf_sz;

if (!partial_pack_sha1) if (!partial_pack_sha1)
continue; continue;