Hello,
This is not sjavac, but just the rather new feature javac-server. It
takes the client/server model from sjavac and applies it to plain old
javac. What this means is that when we invoke javac, it will spawn off a
background server process that stays alive for the duration of the
build. All javac compilations are then sent to this server for
processing from a very thin client. The performance gain comes from
running all javac compilations in a warm JVM.
I believe this has been tested enough to try it as default. If things
fail for a certain usecase, the feature can easily be turned off with
--disable-javac-server. If things go really haywire, we can disable it
again. If we didn't change this now, before feature freeze, it would
never get into JDK9, and I think that would be very sad as faster build
times is generally something everyone wants.
I will compose an email to jdk9-dev announcing this change.
/Erik
On 2015-11-26 05:57, David Holmes wrote:
Hi Erik, Magnus,
Has this been extensively tested with all our build environments?
It's been a while so could you give an overview of exactly how the
sjavac thing works.
Changes that affect every single person building the JDK should not be
rushed through!
Thanks,
David
On 26/11/2015 12:47 AM, Magnus Ihse Bursie wrote:
On 2015-11-25 15:45, Erik Joelsson wrote:
Doh, here you go:
diff -r 358fb90ae6e6 common/autoconf/build-performance.m4
--- a/common/autoconf/build-performance.m4
+++ b/common/autoconf/build-performance.m4
@@ -411,9 +411,9 @@
AC_MSG_RESULT([$ENABLE_SJAVAC])
AC_SUBST(ENABLE_SJAVAC)
- AC_ARG_ENABLE([javac-server],
[AS_HELP_STRING([--enable-javac-server],
- [use only the server part of sjavac for faster javac compiles
@<:@disabled@:>@])],
- [ENABLE_JAVAC_SERVER="${enableval}"],
[ENABLE_JAVAC_SERVER="no"])
+ AC_ARG_ENABLE([javac-server],
[AS_HELP_STRING([--disable-javac-server],
+ [disable javac server @<:@enabled@:>@])],
+ [ENABLE_JAVAC_SERVER="${enableval}"],
[ENABLE_JAVAC_SERVER="yes"])
if test "x$JVM_ARG_OK" = "xfalse"; then
AC_MSG_WARN([Could not set -Xms${MS_VALUE}M -Xmx${MX_VALUE}M,
disabling javac server])
ENABLE_JAVAC_SERVER="no"
Looks good to me.
/Magnus
/Erik
On 2015-11-25 15:38, Magnus Ihse Bursie wrote:
On 2015-11-25 15:11, Erik Joelsson wrote:
Hello,
The --enable-javac-server feature seems to be working well and is
providing considerable speedup when building the JDK. We should make
the option enabled by default.
As an example, on my local machine, a run of "make exploded-image"
without javac server took 00:04:09 and with javac server 00:03:20.
On machines with less cpus I have seen even bigger improvements.
Bug: https://bugs.openjdk.java.net/browse/JDK-8144039
Patch:
diff -r 358fb90ae6e6 common/autoconf/build-performance.m4
--- a/common/autoconf/build-performance.m4
+++ b/common/autoconf/build-performance.m4
@@ -413,7 +413,7 @@
AC_ARG_ENABLE([javac-server],
[AS_HELP_STRING([--enable-javac-server],
[use only the server part of sjavac for faster javac compiles
@<:@disabled@:>@])],
- [ENABLE_JAVAC_SERVER="${enableval}"],
[ENABLE_JAVAC_SERVER="no"])
+ [ENABLE_JAVAC_SERVER="${enableval}"],
[ENABLE_JAVAC_SERVER="yes"])
if test "x$JVM_ARG_OK" = "xfalse"; then
AC_MSG_WARN([Could not set -Xms${MS_VALUE}M -Xmx${MX_VALUE}M,
disabling javac server])
ENABLE_JAVAC_SERVER="no"
diff -r 358fb90ae6e6 common/autoconf/generated-configure.sh
I like that you enable javac-server by default. But the patch was a
bit too hurried. :)
When you change the default value, you are also in fact reversing the
logic of the configure option. As in other such options, the string
listed for AS_HELP_STRING should be "--disable-javac-server", and the
default value listed should be "enabled".
/Magnus
