RFR: JDK-8027584 disable ccache by default

[Mike Duigou]

On Jan 28 2014, at 17:50 , Magnus Ihse Bursie <magnus.ihse.bursie at oracle.com> wrote:

> 
> On 2014-01-29 01:44, Mike Duigou wrote:
>> Looks fine. (I have been caught by the Windows cygwin issue as well).
>> 
>> Do you want to do away with the performance hints entirely? I had another patch for setting memsize which added other hints.
> Yes, I thought we should remove it entirely. I've heard people complain about the .hide-performance-hints file it creates, and frankly, there's probably too much information already in the configure output -- I don't think anyone really reads it. Fredrik put up the hint long time ago, before we started seeing all these issues with ccache, and I was not courageous enogh to remove it earlier. :-)
> 
> But if you have another patch that relies on it, I'll either leave it in place, or you'll have to resurrect it later.

Remove it. I didn't like the aspect of hiding the hints on subsequent configure runs.

> Maybe it would be better to have a separate way to answer the question "how can I increase build performance"? Maybe some kind of tool that analyses common performance issues with the machine and/or the configuration? Rather than to put a lot of output from configure, where even the important stuff drowns...

We already spew a lot during configure. I don't think we should be shy about including warnings if they are relevant. People can just ignore them if they wish (at the price of certain peril).

Mike


> /Magnus
> 
>> 
>> Mike
>> 
>> On Jan 28 2014, at 15:31 , Magnus Ihse Bursie <magnus.ihse.bursie at oracle.com> wrote:
>> 
>>> Bug: https://bugs.openjdk.java.net/browse/JDK-8027584
>>> 
>>> While ccache can be used to speed up recompilations, there are also several issues with ccache. Old versions does not work correctly for the jdk (we try to detect that). It does not work well on other platforms than Linux; on Windows it does not work at all. Nevertheless is ccache enabled on Windows if it is installed, which it apparently tends to be with Cygwin nowadays, requiring the use of --disable-ccache to avoid compilation failure.
>>> 
>>> In many circumstances ccache also does not provide any performance benefit. For instance, new compilations gets a performance hit. Only recompilations benefits.
>>> 
>>> It is better to turn this upside down. This patch makes ccache disabled by default, on all platforms. If you want ccache and are sure you are in a situation that benefits from it, then you can enable it. It also removes the output in configure hinting that ccache should be used.
>>> 
>>> WebRev: http://cr.openjdk.java.net/~ihse/JDK-8027584-disable-ccache-by-default/webrev.01
>>> 
>>> /Magnus
>