Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

Evaluate using Profile-Guided Optimization (PGO) and Post-Link Optimization (PLO) on ctags #3849

Open
zamazan4ik opened this issue Nov 18, 2023 · 2 comments
Open

Evaluate using Profile-Guided Optimization (PGO) and Post-Link Optimization (PLO) on ctags #3849

zamazan4ik opened this issue Nov 18, 2023 · 2 comments

Comments

@zamazan4ik
Copy link

Hi!

Recently I checked Profile-Guided Optimization (PGO) improvements on multiple projects. The results are available here. I also have several examples of applying PGO to the software like ctags:

That's why I think trying to optimize ctags with PGO can be a good idea.

I can suggest the following action points:

  • Perform PGO benchmarks on ctags. And if it shows improvements - add a note to the documentation about possible improvements in ctags performance with PGO.
  • Providing an easier way (e.g. an additional build option) to build scripts with PGO can be helpful for the end-users and maintainers since they will be able to optimize ctags according to their workloads.
  • Optimize pre-built binaries (if it's possible to prepare a good training workload)

Testing Post-Link Optimization techniques (like LLVM BOLT) would be interesting too (Clang and Rustc already use BOLT as an addition to PGO) but I recommend starting from the usual PGO.

Here are some examples of how PGO optimization is integrated in other projects:
@masatake
Copy link
Member

Thank you for this input.

@masatake
Copy link
Member

I tried using the Linux kernel as input. With PGO, it is about 10% faster.

before [yamato@dev64]~/var/codebase% /bin/time ~/bin/ctags --options=NONE -o - -R ~/var/linux > /dev/null
ctags: Notice: No options will be read from files or environment
70.10user 9.89system 1:14.92elapsed 106%CPU (0avgtext 0avgdata 2622720maxresident)k
0inputs 0outputs (0major 887201minor)pagefaults 0swaps

after [yamato@dev64]~/var/codebase% /bin/time ~/bin/ctags --options=NONE -o - -R ~/var/linux > /dev/null
ctags: Notice: No options will be read from files or environment
64.04user 9.78system 1:08.90elapsed 107%CPU (0avgtext 0avgdata 2623040maxresident)k
0inputs 0outputs (0major 920723minor)pagefaults 0swaps

diff --git a/Makefile.am b/Makefile.am
index 4151ef0bf..ca610354b 100644
--- a/Makefile.am
    b/Makefile.am
@@ -67,7  67,7 @@ noinst_LIBRARIES  = libutil.a
 
 noinst_PROGRAMS = utiltest
 
-AM_LDFLAGS = $(EXTRA_LDFLAGS)
 AM_LDFLAGS = $(EXTRA_LDFLAGS) $(COVERAGE_LDFLAGS)
 
 # packcc always uses native compiler even when cross-compiling.
 # packcc cannot use the standard Automake rule.
@@ -127,7  127,7 @@ libutil_a_CPPFLAGS = -I$(srcdir) -I$(srcdir)/main
 libutil_a_CFLAGS   =
 libutil_a_CFLAGS   = $(EXTRA_CFLAGS)
 libutil_a_CFLAGS   = $(WARNING_CFLAGS)
-libutil_a_CFLAGS   = $(COVERAGE_CFLAGS)
 libutil_a_CFLAGS   = $(COVERAGE_CFLAGS) $(PGO_CFLAGS)
 if ENABLE_DEBUGGING
 libutil_a_CPPFLAGS = $(DEBUG_CPPFLAGS)
 endif
@@ -161,7  161,7 @@ libctags_a_CPPFLAGS = -DHAVE_REPOINFO_H
 libctags_a_CFLAGS   =
 libctags_a_CFLAGS   = $(EXTRA_CFLAGS)
 libctags_a_CFLAGS   = $(WARNING_CFLAGS)
-libctags_a_CFLAGS   = $(COVERAGE_CFLAGS)
 libctags_a_CFLAGS   = $(COVERAGE_CFLAGS) $(PGO_CFLAGS)
 libctags_a_CFLAGS   = $(CGCC_CFLAGS)
 libctags_a_CFLAGS   = $(LIBXML_CFLAGS)
 libctags_a_CFLAGS   = $(JANSSON_CFLAGS)
@@ -255,6  255,7 @@ ctags_LDADD  = $(LIBYAML_LIBS)
 ctags_LDADD  = $(SECCOMP_LIBS)
 ctags_LDADD  = $(ICONV_LIBS)
 ctags_LDADD  = $(PCRE2_LIBS)
 ctags_LDFLAGS = $(PGO_LDFLAGS)
 dist_ctags_SOURCES = $(CMDLINE_HEADS) $(CMDLINE_SRCS)
 
 if HOST_MINGW
diff --git a/configure.ac b/configure.ac
index 1d7909e2a..0822ed1a4 100644
--- a/configure.ac
    b/configure.ac
@@ -955,6  955,29 @@ if test "$ETAGS_NAME_EXECUTABLE" != etags ; then
    AC_MSG_NOTICE(Changing name of 'etags' for $ETAGS_NAME_EXECUTABLE)
 fi
 
 # Profile Guided Optimization (PGO)
 # ------------
 PGO_STAGE=none
 PGO_CLFAGS=
 PGO_LDFLAGS=
 
 AC_ARG_WITH([pgo-stage],
   AS_HELP_STRING([--with-pgo-stage=STAGE], [none, bootstrap, or apply]),
   [PGO_STAGE="$withval"])
 
 if test "x$PGO_STAGE" = "xbootstrap"; then
   PGO_CFLAGS='-fprofile-generate=$(abs_top_builddir)'
   PGO_LDFLAGS='-fprofile-generate=$(abs_top_builddir)'
 fi
 
 if test "x$PGO_STAGE" = "xapply"; then
   PGO_CFLAGS='-fprofile-use=$(abs_top_builddir)'
   PGO_LDFLAGS='-fprofile-use=$(abs_top_builddir)'
 fi
 
 AC_SUBST([PGO_CFLAGS])
 AC_SUBST([PGO_LDFLAGS])
 
 # Output files
 # ------------

$ cd ctags
$ ./autogen.sh; make clean;./configure; make -j 100
$ time ./ctags --options=NONE -o - -R ~/var/linux > /dev/null ; : before
$ make clean
$ ./configure --with-pgo-stage=bootstrap ; make -j 100
$ ./ctags --options=NONE -o - -R ~/var/linux > /dev/null ; : profiling
$ ./configure --with-pgo-stage=apply ; make -j 100
$ time ./ctags --options=NONE -o - -R ~/var/linux > /dev/null ; : after

After polishing, I will make a pull request for this.

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Assignees
No one assigned
Labels
None yet
Projects
None yet
Milestone
No milestone
Development

No branches or pull requests
2 participants
@masatake @zamazan4ik