In a repository with many refs, check_refname_component can be a major
contributor to the runtime of some git commands. Provide two
optimized versions of this function: one for machines with SSE4.2, and
one for machines without. One such command is
git rev-parse HEAD
Timings for one particular repo, with about 60k refs, almost all
packed, are:
Old: 35ms
New (no SSE): 29 ms
New (SSE): 25 ms
Many other commands which read refs are also sped up.
Add some tests around 16-byte boundaries to ensure that the SSE
code correctly handles edge-cases.
Signed-off-by: David Turner <dtur...@twitter.com>
---
Makefile | 6 ++
configure.ac | 6 ++
git-compat-util.h | 20 +++++++
refs.c | 164 +++++++++++++++++++++++++++++++++++++++++++++--------
t/t5511-refspec.sh | 13 +++++
5 files changed, 185 insertions(+), 24 deletions(-)
diff --git a/Makefile b/Makefile
index a53f3a8..123e2fc 100644
--- a/Makefile
+++ b/Makefile
@@ -1326,6 +1326,11 @@ else
COMPAT_OBJS += compat/win32mmap.o
endif
endif
+ifdef NO_SSE
+ BASIC_CFLAGS += -DNO_SSE
+else
+ BASIC_CFLAGS += -msse4
+endif
ifdef OBJECT_CREATION_USES_RENAMES
COMPAT_CFLAGS += -DOBJECT_CREATION_MODE=1
endif
@@ -2199,6 +2204,7 @@ GIT-BUILD-OPTIONS: FORCE
@echo NO_PERL=\''$(subst ','\'',$(subst ','\'',$(NO_PERL)))'\' >>$@
@echo NO_PYTHON=\''$(subst ','\'',$(subst ','\'',$(NO_PYTHON)))'\' >>$@
@echo NO_UNIX_SOCKETS=\''$(subst ','\'',$(subst
','\'',$(NO_UNIX_SOCKETS)))'\' >>$@
+ @echo NO_SSE=\''$(subst ','\'',$(subst ','\'',$(NO_SSE)))'\' >>$@
ifdef TEST_OUTPUT_DIRECTORY
@echo TEST_OUTPUT_DIRECTORY=\''$(subst ','\'',$(subst
','\'',$(TEST_OUTPUT_DIRECTORY)))'\' >>$@
endif
diff --git a/configure.ac b/configure.ac
index b711254..71a9429 100644
--- a/configure.ac
+++ b/configure.ac
@@ -382,6 +382,11 @@ AS_HELP_STRING([],[Tcl/Tk interpreter will be found in a
system.]),
GIT_PARSE_WITH(tcltk))
#
+# Declare the with-sse/without-sse options.
+AC_ARG_WITH(sse,
+AS_HELP_STRING([--with-sse],[use SSE instructions (default is YES)]),
+GIT_PARSE_WITH(sse))
+
## Checks for programs.
AC_MSG_NOTICE([CHECKS for programs])
@@ -449,6 +454,7 @@ else
fi
fi
GIT_CONF_SUBST([TCLTK_PATH])
+GIT_CONF_SUBST([NO_SSE])
AC_CHECK_PROGS(ASCIIDOC, [asciidoc])
if test -n "$ASCIIDOC"; then
AC_MSG_CHECKING([for asciidoc version])
diff --git a/git-compat-util.h b/git-compat-util.h
index f6d3a46..cb49850 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -668,6 +668,26 @@ void git_qsort(void *base, size_t nmemb, size_t size,
#endif
#endif
+#ifndef NO_SSE
+#include <nmmintrin.h>
+/* Clang ships with a version of nmmintrin.h that's incomplete; if
+ * necessary, we define the constants that we're going to use. */
+#ifndef _SIDD_UBYTE_OPS
+#define _SIDD_UBYTE_OPS 0x00
+#define _SIDD_CMP_EQUAL_ANY 0x00
+#define _SIDD_CMP_RANGES 0x04
+#define _SIDD_CMP_EQUAL_ORDERED 0x0c
+#define _SIDD_NEGATIVE_POLARITY 0x10
+#endif
+
+/* This is the system memory page size; it's used so that we can read
+ * outside the bounds of an allocation without segfaulting. It is
+ * assumed to be a power of 2. */
+#ifndef PAGE_SIZE
+#define PAGE_SIZE 4096
+#endif
+#endif
+
#ifdef UNRELIABLE_FSTAT
#define fstat_is_reliable() 0
#else
diff --git a/refs.c b/refs.c
index 28d5eca..61a483a 100644
--- a/refs.c
+++ b/refs.c
@@ -5,9 +5,32 @@
#include "dir.h"
#include "string-list.h"
+/* How to handle various characters in refnames:
+ 0: An acceptable character for refs
+ 1: End-of-component
+ 2: ., look for a following . to reject .. in refs
+ 3: @, look for a following { to reject @{ in refs
+ 9: A bad character, reject ref
+
+ See below for the list of illegal characters, from which
+ this table is derived.
+ */
+static unsigned char refname_disposition[] = {
+ 1, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
+ 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
+ 9, 0, 0, 0, 0, 0, 0, 0, 0, 0, 9, 0, 0, 0, 2, 1,
+ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 9, 0, 0, 0, 0, 9,
+ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 9, 9, 0, 9, 0,
+ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 0, 0, 9, 9
+};
+
/*
- * Make sure "ref" is something reasonable to have under ".git/refs/";
- * We do not like it if:
+ * Try to read one refname component from the front of refname.
+ * Return the length of the component found, or -1 if the component is
+ * not legal. It is legal if it is something reasonable to have under
+ * ".git/refs/"; We do not like it if:
*
* - any path component of it begins with ".", or
* - it has double dots "..", or
@@ -15,44 +38,41 @@
* - it ends with a "/".
* - it ends with ".lock"
* - it contains a "\" (backslash)
- */
-/* Return true iff ch is not allowed in reference names. */
-static inline int bad_ref_char(int ch)
-{
- if (((unsigned) ch) <= ' ' || ch == 0x7f ||
- ch == '~' || ch == '^' || ch == ':' || ch == '\\')
- return 1;
- /* 2.13 Pattern Matching Notation */
- if (ch == '*' || ch == '?' || ch == '[') /* Unsupported */
- return 1;
- return 0;
-}
-
-/*
- * Try to read one refname component from the front of refname. Return
- * the length of the component found, or -1 if the component is not
- * legal.
*/
-static int check_refname_component(const char *refname, int flags)
+static int check_refname_component_1(const char *refname, int flags)
{
const char *cp;
char last = '\0';
for (cp = refname; ; cp++) {
- char ch = *cp;
- if (ch == '\0' || ch == '/')
+ unsigned char ch = (unsigned char) *cp;
+ char disp = refname_disposition[ch];
+ switch(disp) {
+ case 0:
+ return -1;
+ case 1:
+ goto out;
+ case 2:
+ if (last == '.')
+ return -1;
+ break;
+ case 3:
+ if (last == '@')
+ return -1;
break;
- if (bad_ref_char(ch))
- return -1; /* Illegal character in refname. */
+ }
+
if (last == '.' && ch == '.')
return -1; /* Refname contains "..". */
if (last == '@' && ch == '{')
return -1; /* Refname contains "@{". */
last = ch;
}
+out:
if (cp == refname)
return 0; /* Component has zero length. */
+
if (refname[0] == '.') {
if (!(flags & REFNAME_DOT_COMPONENT))
return -1; /* Component starts with '.'. */
@@ -68,6 +88,102 @@ static int check_refname_component(const char *refname, int
flags)
return cp - refname;
}
+#ifdef NO_SSE
+#define check_refname_component check_refname_component_1
+#else
+#define BLOCK_SIZE 16
+
+/* Vectorized version of check_refname_component */
+static int check_refname_component(const char *refname, int flags)
+{
+ const __m128i *refname_vec = (__m128i*) refname;
+
+ /* Character ranges for characters forbidden in refs; see
+ * above */
+ static const __v16qi bad = {
+ 0x01, 0x20, 0x7e, 0x7f, 0x5e, 0x5e, 0x3a, 0x3a,
+ 0x5b, 0x5c, 0x2a, 0x2a, 0x3f, 0x3f, 0x3f, 0x3f};
+
+ static const __v16qi nonslashes = {
+ '\001', '/' -1, '/' + 1, 0xff,
+ };
+
+ static const __v16qi dotdot = {'.','.',0};
+ static const __v16qi atcurly = {'@','{',0};
+
+ const __m128i *vp;
+ const char *cp = (const char *)refname_vec;
+
+
+ int dotdotpos = BLOCK_SIZE, atcurlypos = BLOCK_SIZE;
+ for (vp = refname_vec; ; vp++) {
+ __m128i tmp;
+ int endpos;
+
+ /* Handle case of forbidden substrings .. and @{ crossing
+ * sixteen-byte boudaries */
+ if (dotdotpos == 15 && *cp == '.')
+ return -1;
+
+ if (atcurlypos == 15 && *cp == '{')
+ return -1;
+
+ if (((uintptr_t) vp & (PAGE_SIZE - 1)) > PAGE_SIZE - BLOCK_SIZE)
+ /* End-of-page; fall back to slow method for
+ * this entire component. */
+ return check_refname_component_1(refname, flags);
+
+ tmp = _mm_lddqu_si128(vp);
+
+ /* Find slashes or end-of-string. The double-negative
+ * (negative-polarity search for non-slashes) is
+ * necessary so that \0 will also be counted. */
+ endpos = _mm_cmpistri((__m128i) nonslashes, tmp,
+ _SIDD_UBYTE_OPS | _SIDD_CMP_RANGES |
+ _SIDD_NEGATIVE_POLARITY);
+
+ if (_mm_cmpestrc((__m128i) bad, BLOCK_SIZE, tmp, endpos,
+ _SIDD_UBYTE_OPS | _SIDD_CMP_RANGES))
+ return -1;
+
+ dotdotpos = _mm_cmpestri((__m128i) dotdot, 2, tmp, endpos,
+ _SIDD_UBYTE_OPS |
+ _SIDD_CMP_EQUAL_ORDERED);
+ if (dotdotpos < 15)
+ return -1;
+
+ atcurlypos = _mm_cmpestri((__m128i) atcurly, 2, tmp, endpos,
+ _SIDD_UBYTE_OPS |
+ _SIDD_CMP_EQUAL_ORDERED);
+ if (atcurlypos < 15)
+ return -1;
+
+ if (endpos < BLOCK_SIZE) {
+ cp = ((const char*) vp) + endpos;
+ break;
+ }
+ cp = (const char*) vp + BLOCK_SIZE;
+ }
+
+ if (cp == refname)
+ return 0; /* Component has zero length. */
+
+ if (refname[0] == '.') {
+ if (!(flags & REFNAME_DOT_COMPONENT))
+ return -1; /* Component starts with '.'. */
+ /*
+ * Even if leading dots are allowed, don't allow "."
+ * as a component (".." is prevented by a rule above).
+ */
+ if (refname[1] == '\0')
+ return -1; /* Component equals ".". */
+ }
+ if (cp - refname >= 5 && !memcmp(cp - 5, ".lock", 5))
+ return -1; /* Refname ends with ".lock". */
+ return cp - refname;
+}
+#endif
+
int check_refname_format(const char *refname, int flags)
{
int component_len, component_count = 0;
diff --git a/t/t5511-refspec.sh b/t/t5511-refspec.sh
index c289322..0f03f9c 100755
--- a/t/t5511-refspec.sh
+++ b/t/t5511-refspec.sh
@@ -84,4 +84,17 @@ test_refspec push
'refs/heads/*/*/for-linus:refs/remotes/mine/*' invalid
test_refspec fetch 'refs/heads/*/for-linus:refs/remotes/mine/*'
test_refspec push 'refs/heads/*/for-linus:refs/remotes/mine/*'
+test_refspec fetch 'refs/heads/a-very-long-refname'
+test_refspec fetch 'refs/heads/.a-very-long-refname' invalid
+test_refspec fetch 'refs/heads/abcdefgh0123..' invalid
+test_refspec fetch 'refs/heads/abcdefgh01234..' invalid
+test_refspec fetch 'refs/heads/abcdefgh012345..' invalid
+test_refspec fetch 'refs/heads/abcdefgh0123456..' invalid
+test_refspec fetch 'refs/heads/abcdefgh01234567..' invalid
+test_refspec fetch 'refs/heads/abcdefgh0123.a'
+test_refspec fetch 'refs/heads/abcdefgh01234.a'
+test_refspec fetch 'refs/heads/abcdefgh012345.a'
+test_refspec fetch 'refs/heads/abcdefgh0123456.a'
+test_refspec fetch 'refs/heads/abcdefgh01234567.a'
+
test_done
--
2.0.0.rc1.18.gf763c0f
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