I would not complain if the build times went up slightly but I didn't
need 8GB of RAM to do a -j 6 build. ;)
Ali
On Wed, 19 Jan 2011 09:02:13 -0800, nathan binkert <[email protected]>
wrote:
I don't think anyone would have any problems if you did it, no? I've
done many things because they annoyed *me*. The question is, if it
is
worth it. For someone that just rebuilds ISAs all the time, I can
imagine that it is worth it even if it did increase overall build
time
slightly. I think it's a fair trade-off to have a neutral build time
or even a slight increase if it meant that you could get your machine
to work on a file in a better way. My guess is that the major concern
was compiling the same thing many time. One thing to consider when
you're doing this is to use precompiled headers. I'm pretty sure
that
gcc supports them and they could in this instance make a difference.
(Of course, we need to make it work without PCH).
Nate
On Wed, Jan 19, 2011 at 2:21 AM, Gabe Black <[email protected]>
wrote:
I know we've talked about this before, but another reason for
breaking
up ISA generated files occurred to me as I'm waiting for X86_SE to
build. On a machine with a moderate amount of memory, compiling,
say, 8
way parallel works just fine since the memory footprint fits and
there's
enough work for the CPUs to do. If you happen to hit 2 or 3 (or 4 or
5)
of the monster ISA files, though, the memory requirements go up
substantially and you could end up blowing out your memory. This has
happened to me in the past, and I've end up swapping so bad I had to
ssh
in from another machine to kill the build since X stopped
responding.
Needless to say the build time suffers as well. By breaking these
really
big files into smaller chunks, the memory ceiling of builds stays at
a
reasonable level throughout. Otherwise if you hit that bottleneck,
the
only way to move past it is to reduce parallelism for the whole
build
which makes large parts of it suboptimal. Of course this all sounds
nice
but is a pain or at least a lot of work to implement, and there was
a
sentiment (which is quite possibly justified) that the shorter
compile
times * more compiles comes out in the wash. I think this issue,
however, is harder to ignore and a good reason to give this more
thought.
Gabe
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