RFR: 8201788: Number of make jobs wrong for bootcycle-images target (original) (raw)

Severin Gehwolf sgehwolf at redhat.com
Fri Apr 20 07:51:14 UTC 2018

Hi Magnus,

On Thu, 2018-04-19 at 20:58 +0200, Magnus Ihse Bursie wrote:

Looks good to me too. Thanks for doing it this way.

Thanks for the review, pushed (jdk-submit came back clean).

Cheers, Severin

/Magnus

> 19 apr. 2018 kl. 20:08 skrev Severin Gehwolf <sgehwolf at redhat.com>: > > Hi Erik, > > > On Thu, 2018-04-19 at 09:03 -0700, Erik Joelsson wrote: > > Hello, > > > > > On 2018-04-19 08:58, Severin Gehwolf wrote: > > > Hi Erik, > > > > > > Thanks for the review! > > > > > > > On Thu, 2018-04-19 at 08:25 -0700, Erik Joelsson wrote: > > > > Hello Severin, > > > > > > > > The suggested patch is not a good idea because by setting -j > > > > on the make > > > > command line in a sub make disables the job server. The job > > > > server is > > > > what makes it possible to do recursive make with a fixed > > > > global number > > > > of "jobs". If you do as you suggest, you essentially double > > > > the total > > > > number of available "jobs". The original make retains its > > > > number and the > > > > submake get a full other set of the same number of "jobs". > > > > > > I'm confused. Isn't this what the status quo is? With the > > > difference > > > that it's currently setting JOBS="", thus allowing sub-make to > > > add any > > > number of jobs. It'll result in sub-make calling "make -j" > > > where '-j' > > > won't get an argument. If that's the case it's disabling the > > > job server > > > currently too, no? Then again, why would we see build failures? > > > I must > > > be missing something. > > > > Ah, correct, the current code is also disabling the job server, > > that is > > the core of the issue. :) I'm sorry I wasn't clear on that, it > > was just > > so obvious in my world. Any -j flag in a sub make disables the > > job > > server connection between the calling make an the sub make. > > Setting it > > to -j without argument is going to wreck a lot more havoc than > > setting > > it to something like close to "number-of-cpus", which your first > > suggestion does. The former more or less creates a fork bomb, > > while the > > latter only over allocates by a factor 2 at the worst. > > OK. That does make it sound like that "disabling the job server" > and > creating more jobs are independent problems. I somehow thought in > my > naive world that disabling the job server puts an end to the fork- > bomb > ;-) > > Thanks for the clarification. > > > > > My suggestion was to explicitly turn off the setting of JOBS > > > > based on a > > > > special variable flag, just for bootcycle builds. Magnus > > > > didn't like > > > > that because introducing a lot of special flags everywhere > > > > will > > > > eventually lead to very convoluted code. He instead suggested > > > > that the > > > > bootcycle call should continue to set JOBS to empty, then the > > > > code in > > > > Init.gmk which sets the -j flag should be changed to: > > > > > > > > (if(if (if(JOBS), -j=$(JOBS)) > > > > > > > > So that we only set -j if JOBS have a value. My only > > > > objection to that > > > > was that we then no longer support the case of letting make > > > > run with any > > > > number of jobs. I do agree that removing that option isn't a > > > > big deal. > > > > You can always work around it by setting JOBS to a very large > > > > number > > > > (like 1000, which is way more than any possible concurrency > > > > currently > > > > possible in the build anyway). > > > > > > > > So to summarize, I think the correct solution to the bug is > > > > the snippet > > > > above. > > > > > > Alright. How does this webrev look to you? > > > http://cr.openjdk.java.net/~sgehwolf/webrevs/JDK-8201788/webrev > > > .01/ > > > > Yes, this looks good. Consider it reviewed. > > Great, thanks for the review! I'm currently running this through > jdk- > submit. Hopefully I'll get some response this time :) > > Cheers, > Severin > > > /Erik > > > Thanks, > > > Severin > > > > > > > /Erik > > > > > > > > > > > > > On 2018-04-19 07:46, Severin Gehwolf wrote: > > > > > Hi, > > > > > > > > > > Bug: https://bugs.openjdk.java.net/browse/JDK-8201788 > > > > > > > > > > I'd like to get a fix in for an old discussion which > > > > > already happened a > > > > > while ago: > > > > > http://mail.openjdk.java.net/pipermail/build-dev/2017-April > > > > > /018929.html > > > > > > > > > > The issue is that for bootcycle-images target a recursive > > > > > call to make > > > > > is being called with 'JOBS=""' which results in a call to > > > > > "make -j". > > > > > Thus, make is free to use as many jobs as it would like. > > > > > This may cause > > > > > for the occasional build failure. It has for us in the > > > > > past. > > > > > > > > > > In this old thread above a patch like this was discouraged, > > > > > unless I > > > > > misunderstood something. > > > > > > > > > > diff --git a/make/Main.gmk b/make/Main.gmk > > > > > --- a/make/Main.gmk > > > > > +++ b/make/Main.gmk > > > > > @@ -321,7 +321,7 @@ > > > > > ifneq ($(COMPILETYPE), cross) > > > > > $(call LogWarn, Boot cycle build step 2: > > > > > Building a new JDK image using previously built image) > > > > > +$(MAKE) (MAKEARGS)−f(MAKEARGS) -f (MAKEARGS)−f(TOPDIR)/make/Init.gmk _> > > > > PARALLELTARGETS=$(BOOTCYCLETARGET) _ > > > > > - JOBS= SPEC=$(dir $(SPEC))bootcycle-spec.gmk > > > > > main > > > > > + JOBS=$(JOBS) SPEC=$(dir $(SPEC))bootcycle- > > > > > spec.gmk main > > > > > else > > > > > $(call LogWarn, Boot cycle build disabled when > > > > > cross compiling) > > > > > endif > > > > > > > > > > It's my understanding that such a fix would pass down the > > > > > relevant JOBS > > > > > setting to sub-make and, thus, producing the desired 'make > > > > > -j ' > > > > > call? What am I missing? If somebody wants to shoot > > > > > themselves in the > > > > > foot by doing: > > > > > > > > > > configure ... > > > > > make JOBS= > > > > > > > > > > That should be fine as it would just result in "make -j" > > > > > calls without > > > > > arguments. The common case where the JOBS setting comes > > > > > from configure > > > > > would be fixed, though. bootcycle-images target would > > > > > result in "make > > > > > -j ". > > > > > > > > > > Thoughts? Suggestions? > > > > > > > > > > Thanks, > > > > > Severin > > > >

More information about the build-dev mailing list