[zorg] r174421 - Adding cortex-a15 experimental buildbot

[David Tweed]

On 5 February 2013 22:51, Dmitri Gribenko <gribozavr at gmail.com> wrote:

> It might be easier to change to ninja than use ccache.

It would be best is to use both :)

 

> Yes, I only said that because David Tweed reported some random crashes on
Panda boards when using CCache, so I'm not too keen on leaving it by default
on buildbots.

 

Hi. I'm a little bit confused: ccache helps in the case that you insist on
doing a "make clean" before doing a rebuild (because a significant number of
the files haven't actually changed but you've blown away the .o files) while
ninja (AIUI) does dependency tracking in the non "make clean" case.
Personally I think that deliberately not doing a make clean is safe enough
to be worth trying on a buildbot, particularly if it's the only one of its
kind. Looking at the output from the a15 buildbot it looks like you are
choosing to do a "make clean".

 

FWIW, it wasn't quite crashes that I saw using ccache on pandaboards but
complete lockups of the board. I don't recall seeing anything that looked
like corruption or a crash (though I often didn't look at results that hard
so might possibly have missed occasions.) The tentative hypothesis was that
doing a normal compile the I/O demand is limited by the rate at which the
CPU can do an actual compile (which effectively slows things down), while
when using ccache you can get occasions when the I/O demand is limited by
the rate at which the CPU can hash files (which is quite fast even on mobile
CPUs) and this higher I/O rate was causing something to lock up on the
board. But that was just a hypothesis.

 

Cheers,

Dave
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