The change looks ok from a build perspective.
Regarding optimization for size on Macos, I don't believe those settings
have changed since Xcode changed from GCC to Clang. It could very well
be that we would benefit from different optimization settings on Macos.
Investigating that seems like out of scope for this change though, but
certainly something that would be interesting if someone felt like doing
an investigation.
/Erik
On 2019-04-28 22:30, Man Cao wrote:
Hi Jiangli,
Thanks for the feedback. I wasn't aware that we optimize for size on
MacOSX, so I changed it to Linux-only:
https://cr.openjdk.java.net/~manc/8220388/webrev.02/
Size and performance comparison was included in
https://bugs.openjdk.java.net/browse/JDK-8220388, copying sizes below:
Sizes of libjvm.so:
GoogGcc-default: 25369007
GoogClang-default: 22946876
GoogClang-100kInline: 24681265
GCC version: 4.9
Clang version: trunk r355087
-Man
On Sat, Apr 27, 2019 at 4:57 PM Jiangli Zhou <jiangliz...@google.com> wrote:
Hi Man,
I have a question. Should the -inlinehint-threshold change be applied
to linux only? The following in flags-cflags.m4 indicates it's
optimized for size on MacOSX currently.
elif test "x$TOOLCHAIN_TYPE" = xclang; then
if test "x$OPENJDK_TARGET_OS" = xmacosx; then
# On MacOSX we optimize for size, something
# we should do for all platforms?
C_O_FLAG_HIGHEST_JVM="-Os"
C_O_FLAG_HIGHEST="-Os"
C_O_FLAG_HI="-Os"
C_O_FLAG_NORM="-Os"
C_O_FLAG_DEBUG_JVM=""
else
C_O_FLAG_HIGHEST_JVM="-O3"
C_O_FLAG_HIGHEST="-O3"
C_O_FLAG_HI="-O3"
C_O_FLAG_NORM="-O2"
C_O_FLAG_DEBUG_JVM="-O0"
fi
It would be helpful to share the binary size comparison with gcc and
clang (with -inlinehint-threshold=100000 change).
Regards,
Jiangli
On Fri, Apr 26, 2019 at 6:38 PM Man Cao <m...@google.com> wrote:
(Adding build-dev@openjdk.java.net)
Maybe some one from build-dev could review or comment on this change?
-Man
On Mon, Mar 11, 2019 at 12:55 PM Man Cao <m...@google.com> wrote:
Thanks for the suggestion.
Yes, I agree it makes sense to increase -inlinehint-threshold only for
"release" build.
However, I'm not sure if adding per-file CXX flags in
JvmOverrideFiles.gmk is a better approach.
The root problem is that Clang is more likely to ignore the "inline"
keyword than GCC, causing unexpected performance problems. G1 pause time
could be just one of many potential performance problems.
If we take the effort to identify which files need the
-inlinehint-threshold flag, we'd better take a step further to identify the
functions that should be ALWAYSINLINE.
Thus I think it is more maintainable to do one the following:
(1) Identify the functions that should be "ALWAYSINLINE" instead of
"inline", and avoid adding "-inlinehint-threshold" for Clang altogether.
This requires much more work.
(2) Increase "-inlinehint-threshold" for all files in "release" build
for Clang.
Note that -inlinehint-threshold is different from -inline-threshold, as
-inlinehint-threshold only affects methods marked as "inline" and shouldn't
unnecessarily bloat up the binary size for release build.
So I added an extra guard "x$DEBUG_LEVEL" = xrelease;" in
flags-cflags.m4:
https://cr.openjdk.java.net/~manc/8220388/webrev.01/
-Man
