Use libxxhash for hashing, if present

XXHash is faster than htab_hash_string:
------------------------------------------------------------
Benchmark                     Time           CPU Iterations
------------------------------------------------------------
BM_xxh3                      11 ns         11 ns   65887249
BM_xxh32                     19 ns         19 ns   36511877
BM_xxh64                     16 ns         16 ns   42964585
BM_hash_string              182 ns        182 ns    3853125
BM_iterative_hash            77 ns         77 ns    9087638

Unfortunately, XXH3 is still experimental (see
https://github.com/Cyan4973/xxHash#user-content-new-experimental-hash-algorithm)

However, regular XXH64 is still a lot faster than
htab_hash_string per my benchmark above. I used the
following string for the benchmark:
static constexpr char str[] = "_ZZZL13make_gdb_typeP7gdbarchP10tdesc_typeEN16gdb_type_creator19make_gdb_type_flagsEPK22tdesc_type_with_fieldsE19__PRETTY_FUNCTION__";

htab_hash_string is currently 4.35% + 7.98% (rehashing) of gdb
startup when attaching to Chrome's content_shell.

An additional 5.21% is spent in msymbol_hash, which does not use
this hash function. Unfortunately, since it has to lowercase the
string, it can't use this hash function.
BM_msymbol_hash                52 ns         52 ns   13281495

It may be worth investigating if strlen+XXHash is still faster than
htab_hash_string, which would make it easier to use in more places.

Debian ships xxhash as libxxhash{0,-dev}. Fedora ships it as xxhash-devel.

gdb/ChangeLog:

2019-10-22  Christian Biesinger  <cbiesinger@google.com>

	* Makefile.in: Link with libxxhash.
	* config.in: Regenerate.
	* configure: Regenerate.
	* configure.ac: Search for libxxhash.
	* utils.c (fast_hash): Use xxhash if present.

Change-Id: Icab218388b9f829522ed3977f04301ae6d4fc4ca
This commit is contained in:
Christian Biesinger 2019-09-27 13:32:07 -05:00
parent 1a6ff1a96b
commit ccb1ba6229
7 changed files with 545 additions and 2 deletions

View File

@ -1,3 +1,11 @@
2019-10-22 Christian Biesinger <cbiesinger@google.com>
* Makefile.in: Link with libxxhash.
* config.in: Regenerate.
* configure: Regenerate.
* configure.ac: Search for libxxhash.
* utils.c (fast_hash): Use xxhash if present.
2019-10-22 Christian Biesinger <cbiesinger@google.com>
* utils.h (fast_hash): New function.

View File

@ -187,10 +187,14 @@ LIBEXPAT = @LIBEXPAT@
# Where is lzma? This will be empty if lzma was not available.
LIBLZMA = @LIBLZMA@
# Where is libbabeltrace? This will be empty if lbabeltrace was not
# Where is libbabeltrace? This will be empty if libbabeltrace was not
# available.
LIBBABELTRACE = @LIBBABELTRACE@
# Where is libxxhash? This will be empty if libxxhash was not
# available.
LIBXXHASH = @LIBXXHASH@
# Where is libipt? This will be empty if libipt was not available.
LIBIPT = @LIBIPT@
@ -597,7 +601,7 @@ CLIBS = $(SIM) $(READLINE) $(OPCODES) $(BFD) $(LIBCTF) $(ZLIB) \
@LIBS@ @GUILE_LIBS@ @PYTHON_LIBS@ \
$(LIBEXPAT) $(LIBLZMA) $(LIBBABELTRACE) $(LIBIPT) \
$(LIBIBERTY) $(WIN32LIBS) $(LIBGNU) $(LIBICONV) $(LIBMPFR) \
$(SRCHIGH_LIBS)
$(SRCHIGH_LIBS) $(LIBXXHASH)
CDEPS = $(NAT_CDEPS) $(SIM) $(BFD) $(READLINE_DEPS) $(LIBCTF) \
$(OPCODES) $(INTL_DEPS) $(LIBIBERTY) $(CONFIG_DEPS) $(LIBGNU)

View File

@ -255,6 +255,9 @@
/* Define to 1 if you have the <libunwind-ia64.h> header file. */
#undef HAVE_LIBUNWIND_IA64_H
/* Define if you have the xxhash library. */
#undef HAVE_LIBXXHASH
/* Define to 1 if you have the <linux/elf.h> header file. */
#undef HAVE_LINUX_ELF_H

497
gdb/configure vendored
View File

@ -628,6 +628,9 @@ GDB_TRANSFORM_NAME
XSLTPROC
NM_H
GDB_NM_FILE
LTLIBXXHASH
LIBXXHASH
HAVE_LIBXXHASH
LTLIBBABELTRACE
LIBBABELTRACE
HAVE_LIBBABELTRACE
@ -898,6 +901,8 @@ enable_sim
enable_gdbserver
with_babeltrace
with_libbabeltrace_prefix
with_xxhash
with_libxxhash_prefix
enable_unit_tests
'
ac_precious_vars='build_alias
@ -1628,6 +1633,9 @@ Optional Packages:
--with-babeltrace include babeltrace support (auto/yes/no)
--with-libbabeltrace-prefix[=DIR] search for libbabeltrace in DIR/include and DIR/lib
--without-libbabeltrace-prefix don't search for libbabeltrace in includedir and libdir
--with-xxhash use libxxhash for hashing (faster) (auto/yes/no)
--with-libxxhash-prefix[=DIR] search for libxxhash in DIR/include and DIR/lib
--without-libxxhash-prefix don't search for libxxhash in includedir and libdir
Some influential environment variables:
CC C compiler command
@ -17557,6 +17565,495 @@ $as_echo "$as_me: WARNING: babeltrace is missing or unusable; GDB is unable to r
fi
fi
# Check for xxhash
# Check whether --with-xxhash was given.
if test "${with_xxhash+set}" = set; then :
withval=$with_xxhash;
else
with_xxhash=auto
fi
if test "x$with_xxhash" != "xno"; then
use_additional=yes
acl_save_prefix="$prefix"
prefix="$acl_final_prefix"
acl_save_exec_prefix="$exec_prefix"
exec_prefix="$acl_final_exec_prefix"
eval additional_includedir=\"$includedir\"
eval additional_libdir=\"$libdir\"
exec_prefix="$acl_save_exec_prefix"
prefix="$acl_save_prefix"
# Check whether --with-libxxhash-prefix was given.
if test "${with_libxxhash_prefix+set}" = set; then :
withval=$with_libxxhash_prefix;
if test "X$withval" = "Xno"; then
use_additional=no
else
if test "X$withval" = "X"; then
acl_save_prefix="$prefix"
prefix="$acl_final_prefix"
acl_save_exec_prefix="$exec_prefix"
exec_prefix="$acl_final_exec_prefix"
eval additional_includedir=\"$includedir\"
eval additional_libdir=\"$libdir\"
exec_prefix="$acl_save_exec_prefix"
prefix="$acl_save_prefix"
else
additional_includedir="$withval/include"
additional_libdir="$withval/lib"
fi
fi
fi
LIBXXHASH=
LTLIBXXHASH=
INCXXHASH=
rpathdirs=
ltrpathdirs=
names_already_handled=
names_next_round='xxhash '
while test -n "$names_next_round"; do
names_this_round="$names_next_round"
names_next_round=
for name in $names_this_round; do
already_handled=
for n in $names_already_handled; do
if test "$n" = "$name"; then
already_handled=yes
break
fi
done
if test -z "$already_handled"; then
names_already_handled="$names_already_handled $name"
uppername=`echo "$name" | sed -e 'y|abcdefghijklmnopqrstuvwxyz./-|ABCDEFGHIJKLMNOPQRSTUVWXYZ___|'`
eval value=\"\$HAVE_LIB$uppername\"
if test -n "$value"; then
if test "$value" = yes; then
eval value=\"\$LIB$uppername\"
test -z "$value" || LIBXXHASH="${LIBXXHASH}${LIBXXHASH:+ }$value"
eval value=\"\$LTLIB$uppername\"
test -z "$value" || LTLIBXXHASH="${LTLIBXXHASH}${LTLIBXXHASH:+ }$value"
else
:
fi
else
found_dir=
found_la=
found_so=
found_a=
if test $use_additional = yes; then
if test -n "$shlibext" && test -f "$additional_libdir/lib$name.$shlibext"; then
found_dir="$additional_libdir"
found_so="$additional_libdir/lib$name.$shlibext"
if test -f "$additional_libdir/lib$name.la"; then
found_la="$additional_libdir/lib$name.la"
fi
else
if test -f "$additional_libdir/lib$name.$libext"; then
found_dir="$additional_libdir"
found_a="$additional_libdir/lib$name.$libext"
if test -f "$additional_libdir/lib$name.la"; then
found_la="$additional_libdir/lib$name.la"
fi
fi
fi
fi
if test "X$found_dir" = "X"; then
for x in $LDFLAGS $LTLIBXXHASH; do
acl_save_prefix="$prefix"
prefix="$acl_final_prefix"
acl_save_exec_prefix="$exec_prefix"
exec_prefix="$acl_final_exec_prefix"
eval x=\"$x\"
exec_prefix="$acl_save_exec_prefix"
prefix="$acl_save_prefix"
case "$x" in
-L*)
dir=`echo "X$x" | sed -e 's/^X-L//'`
if test -n "$shlibext" && test -f "$dir/lib$name.$shlibext"; then
found_dir="$dir"
found_so="$dir/lib$name.$shlibext"
if test -f "$dir/lib$name.la"; then
found_la="$dir/lib$name.la"
fi
else
if test -f "$dir/lib$name.$libext"; then
found_dir="$dir"
found_a="$dir/lib$name.$libext"
if test -f "$dir/lib$name.la"; then
found_la="$dir/lib$name.la"
fi
fi
fi
;;
esac
if test "X$found_dir" != "X"; then
break
fi
done
fi
if test "X$found_dir" != "X"; then
LTLIBXXHASH="${LTLIBXXHASH}${LTLIBXXHASH:+ }-L$found_dir -l$name"
if test "X$found_so" != "X"; then
if test "$enable_rpath" = no || test "X$found_dir" = "X/usr/lib"; then
LIBXXHASH="${LIBXXHASH}${LIBXXHASH:+ }$found_so"
else
haveit=
for x in $ltrpathdirs; do
if test "X$x" = "X$found_dir"; then
haveit=yes
break
fi
done
if test -z "$haveit"; then
ltrpathdirs="$ltrpathdirs $found_dir"
fi
if test "$hardcode_direct" = yes; then
LIBXXHASH="${LIBXXHASH}${LIBXXHASH:+ }$found_so"
else
if test -n "$hardcode_libdir_flag_spec" && test "$hardcode_minus_L" = no; then
LIBXXHASH="${LIBXXHASH}${LIBXXHASH:+ }$found_so"
haveit=
for x in $rpathdirs; do
if test "X$x" = "X$found_dir"; then
haveit=yes
break
fi
done
if test -z "$haveit"; then
rpathdirs="$rpathdirs $found_dir"
fi
else
haveit=
for x in $LDFLAGS $LIBXXHASH; do
acl_save_prefix="$prefix"
prefix="$acl_final_prefix"
acl_save_exec_prefix="$exec_prefix"
exec_prefix="$acl_final_exec_prefix"
eval x=\"$x\"
exec_prefix="$acl_save_exec_prefix"
prefix="$acl_save_prefix"
if test "X$x" = "X-L$found_dir"; then
haveit=yes
break
fi
done
if test -z "$haveit"; then
LIBXXHASH="${LIBXXHASH}${LIBXXHASH:+ }-L$found_dir"
fi
if test "$hardcode_minus_L" != no; then
LIBXXHASH="${LIBXXHASH}${LIBXXHASH:+ }$found_so"
else
LIBXXHASH="${LIBXXHASH}${LIBXXHASH:+ }-l$name"
fi
fi
fi
fi
else
if test "X$found_a" != "X"; then
LIBXXHASH="${LIBXXHASH}${LIBXXHASH:+ }$found_a"
else
LIBXXHASH="${LIBXXHASH}${LIBXXHASH:+ }-L$found_dir -l$name"
fi
fi
additional_includedir=
case "$found_dir" in
*/lib | */lib/)
basedir=`echo "X$found_dir" | sed -e 's,^X,,' -e 's,/lib/*$,,'`
additional_includedir="$basedir/include"
;;
esac
if test "X$additional_includedir" != "X"; then
if test "X$additional_includedir" != "X/usr/include"; then
haveit=
if test "X$additional_includedir" = "X/usr/local/include"; then
if test -n "$GCC"; then
case $host_os in
linux*) haveit=yes;;
esac
fi
fi
if test -z "$haveit"; then
for x in $CPPFLAGS $INCXXHASH; do
acl_save_prefix="$prefix"
prefix="$acl_final_prefix"
acl_save_exec_prefix="$exec_prefix"
exec_prefix="$acl_final_exec_prefix"
eval x=\"$x\"
exec_prefix="$acl_save_exec_prefix"
prefix="$acl_save_prefix"
if test "X$x" = "X-I$additional_includedir"; then
haveit=yes
break
fi
done
if test -z "$haveit"; then
if test -d "$additional_includedir"; then
INCXXHASH="${INCXXHASH}${INCXXHASH:+ }-I$additional_includedir"
fi
fi
fi
fi
fi
if test -n "$found_la"; then
save_libdir="$libdir"
case "$found_la" in
*/* | *\\*) . "$found_la" ;;
*) . "./$found_la" ;;
esac
libdir="$save_libdir"
for dep in $dependency_libs; do
case "$dep" in
-L*)
additional_libdir=`echo "X$dep" | sed -e 's/^X-L//'`
if test "X$additional_libdir" != "X/usr/lib"; then
haveit=
if test "X$additional_libdir" = "X/usr/local/lib"; then
if test -n "$GCC"; then
case $host_os in
linux*) haveit=yes;;
esac
fi
fi
if test -z "$haveit"; then
haveit=
for x in $LDFLAGS $LIBXXHASH; do
acl_save_prefix="$prefix"
prefix="$acl_final_prefix"
acl_save_exec_prefix="$exec_prefix"
exec_prefix="$acl_final_exec_prefix"
eval x=\"$x\"
exec_prefix="$acl_save_exec_prefix"
prefix="$acl_save_prefix"
if test "X$x" = "X-L$additional_libdir"; then
haveit=yes
break
fi
done
if test -z "$haveit"; then
if test -d "$additional_libdir"; then
LIBXXHASH="${LIBXXHASH}${LIBXXHASH:+ }-L$additional_libdir"
fi
fi
haveit=
for x in $LDFLAGS $LTLIBXXHASH; do
acl_save_prefix="$prefix"
prefix="$acl_final_prefix"
acl_save_exec_prefix="$exec_prefix"
exec_prefix="$acl_final_exec_prefix"
eval x=\"$x\"
exec_prefix="$acl_save_exec_prefix"
prefix="$acl_save_prefix"
if test "X$x" = "X-L$additional_libdir"; then
haveit=yes
break
fi
done
if test -z "$haveit"; then
if test -d "$additional_libdir"; then
LTLIBXXHASH="${LTLIBXXHASH}${LTLIBXXHASH:+ }-L$additional_libdir"
fi
fi
fi
fi
;;
-R*)
dir=`echo "X$dep" | sed -e 's/^X-R//'`
if test "$enable_rpath" != no; then
haveit=
for x in $rpathdirs; do
if test "X$x" = "X$dir"; then
haveit=yes
break
fi
done
if test -z "$haveit"; then
rpathdirs="$rpathdirs $dir"
fi
haveit=
for x in $ltrpathdirs; do
if test "X$x" = "X$dir"; then
haveit=yes
break
fi
done
if test -z "$haveit"; then
ltrpathdirs="$ltrpathdirs $dir"
fi
fi
;;
-l*)
names_next_round="$names_next_round "`echo "X$dep" | sed -e 's/^X-l//'`
;;
*.la)
names_next_round="$names_next_round "`echo "X$dep" | sed -e 's,^X.*/,,' -e 's,^lib,,' -e 's,\.la$,,'`
;;
*)
LIBXXHASH="${LIBXXHASH}${LIBXXHASH:+ }$dep"
LTLIBXXHASH="${LTLIBXXHASH}${LTLIBXXHASH:+ }$dep"
;;
esac
done
fi
else
LIBXXHASH="${LIBXXHASH}${LIBXXHASH:+ }-l$name"
LTLIBXXHASH="${LTLIBXXHASH}${LTLIBXXHASH:+ }-l$name"
fi
fi
fi
done
done
if test "X$rpathdirs" != "X"; then
if test -n "$hardcode_libdir_separator"; then
alldirs=
for found_dir in $rpathdirs; do
alldirs="${alldirs}${alldirs:+$hardcode_libdir_separator}$found_dir"
done
acl_save_libdir="$libdir"
libdir="$alldirs"
eval flag=\"$hardcode_libdir_flag_spec\"
libdir="$acl_save_libdir"
LIBXXHASH="${LIBXXHASH}${LIBXXHASH:+ }$flag"
else
for found_dir in $rpathdirs; do
acl_save_libdir="$libdir"
libdir="$found_dir"
eval flag=\"$hardcode_libdir_flag_spec\"
libdir="$acl_save_libdir"
LIBXXHASH="${LIBXXHASH}${LIBXXHASH:+ }$flag"
done
fi
fi
if test "X$ltrpathdirs" != "X"; then
for found_dir in $ltrpathdirs; do
LTLIBXXHASH="${LTLIBXXHASH}${LTLIBXXHASH:+ }-R$found_dir"
done
fi
ac_save_CPPFLAGS="$CPPFLAGS"
for element in $INCXXHASH; do
haveit=
for x in $CPPFLAGS; do
acl_save_prefix="$prefix"
prefix="$acl_final_prefix"
acl_save_exec_prefix="$exec_prefix"
exec_prefix="$acl_final_exec_prefix"
eval x=\"$x\"
exec_prefix="$acl_save_exec_prefix"
prefix="$acl_save_prefix"
if test "X$x" = "X$element"; then
haveit=yes
break
fi
done
if test -z "$haveit"; then
CPPFLAGS="${CPPFLAGS}${CPPFLAGS:+ }$element"
fi
done
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for libxxhash" >&5
$as_echo_n "checking for libxxhash... " >&6; }
if ${ac_cv_libxxhash+:} false; then :
$as_echo_n "(cached) " >&6
else
ac_save_LIBS="$LIBS"
LIBS="$LIBS $LIBXXHASH"
cat confdefs.h - <<_ACEOF >conftest.$ac_ext
/* end confdefs.h. */
#include <xxhash.h>
int
main ()
{
XXH32("foo", 3, 0);
;
return 0;
}
_ACEOF
if ac_fn_c_try_link "$LINENO"; then :
ac_cv_libxxhash=yes
else
ac_cv_libxxhash=no
fi
rm -f core conftest.err conftest.$ac_objext \
conftest$ac_exeext conftest.$ac_ext
LIBS="$ac_save_LIBS"
fi
{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_libxxhash" >&5
$as_echo "$ac_cv_libxxhash" >&6; }
if test "$ac_cv_libxxhash" = yes; then
HAVE_LIBXXHASH=yes
$as_echo "#define HAVE_LIBXXHASH 1" >>confdefs.h
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking how to link with libxxhash" >&5
$as_echo_n "checking how to link with libxxhash... " >&6; }
{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $LIBXXHASH" >&5
$as_echo "$LIBXXHASH" >&6; }
else
HAVE_LIBXXHASH=no
CPPFLAGS="$ac_save_CPPFLAGS"
LIBXXHASH=
LTLIBXXHASH=
fi
if test "$HAVE_LIBXXHASH" != yes; then
if test "$with_xxhash" = yes; then
as_fn_error $? "xxhash is missing or unusable" "$LINENO" 5
fi
fi
if test "x$with_xxhash" = "xauto"; then
with_xxhash="$HAVE_LIBXXHASH"
fi
fi
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether to use xxhash" >&5
$as_echo_n "checking whether to use xxhash... " >&6; }
{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $with_xxhash" >&5
$as_echo "$with_xxhash" >&6; }
NM_H=
rm -f nm.h
if test "${nativefile}" != ""; then

View File

@ -2217,6 +2217,29 @@ else
fi
fi
# Check for xxhash
AC_ARG_WITH(xxhash,
AC_HELP_STRING([--with-xxhash], [use libxxhash for hashing (faster) (auto/yes/no)]),
[], [with_xxhash=auto])
if test "x$with_xxhash" != "xno"; then
AC_LIB_HAVE_LINKFLAGS([xxhash], [],
[#include <xxhash.h>],
[XXH32("foo", 3, 0);
])
if test "$HAVE_LIBXXHASH" != yes; then
if test "$with_xxhash" = yes; then
AC_MSG_ERROR([xxhash is missing or unusable])
fi
fi
if test "x$with_xxhash" = "xauto"; then
with_xxhash="$HAVE_LIBXXHASH"
fi
fi
AC_MSG_CHECKING([whether to use xxhash])
AC_MSG_RESULT([$with_xxhash])
NM_H=
rm -f nm.h
if test "${nativefile}" != ""; then

View File

@ -36,6 +36,10 @@
#include <pc.h>
#endif
#ifdef HAVE_LIBXXHASH
#include <xxhash.h>
#endif
#include <signal.h>
#include "gdbcmd.h"
#include "serial.h"

View File

@ -574,7 +574,11 @@ extern void copy_bitwise (gdb_byte *dest, ULONGEST dest_offset,
static inline unsigned int
fast_hash (const char* str, size_t len)
{
#ifdef HAVE_LIBXXHASH
return XXH64 (str, len, 0);
#else
return iterative_hash (str, len, 0);
#endif
}
#endif /* UTILS_H */