Re: [gentoo-user] Re: Simultaneously emerging multiple packages with same dependencies

[J. Roeleveld]

On Thursday 27 January 2011 23:05:22 Paul Hartman wrote:
> On Thu, Jan 27, 2011 at 3:46 PM, J. Roeleveld <joost@××××××××.org> wrote:
> > On Thursday 27 January 2011 21:25:02 Paul Hartman wrote:
> >> On Thu, Jan 27, 2011 at 2:15 PM, Nikos Chantziaras <realnc@×××××.de>
wrote:
> >> > On 01/27/2011 09:41 PM, Dale wrote:
> >> >> YoYo Siska wrote:
> >> >>> Yes.
> >> >>> It might not be perfect, but mostly it works pretty well.
> >> >>> Once make started 10 or so process, which ate all my ram, because I
> >> >>> forgot to reenable swap, when I was playing with something before
> >> >>> that
> >> >>>
> >> >>> :)
> >> >>>
> >> >>> yoyo
> >> >>
> >> >> I noticed the same thing with mine. It used a LOT of ram. I have 4Gbs
> >> >> and it was up to about 3Gbs at one point and using some swap as well.
> >> >> I'm hoping to max out to 16Gbs as soon as I can. May upgrade to a 6
> >> >> core CPU too.
> >> >>
> >> >> I wonder how much faster it would be if the work directory is put on
> >> >> tmpfs? With 16Gbs, that should work even for OOo.
> >> >
> >> > Btw, if you're using more instances than the amount of CPUs, the
> >> > result will be slow-down.
> >> >
> >> > With the default kernel scheduler, best if amount of CPUs + 1.  (On a
> >> > 4-core, that's -j5).
> >>
> >> Once, when building my kernel, I accidentally forgot to specify the
> >> number of makes and ran "make -j all". That was a really bad idea, the
> >> system became totally unresponsive for quite a long time, much longer
> >> than normal kernel build time, but it did eventually finish!
> >
> > I have found that multi-core systems with sufficient memory can handle
> > "-j" (no value) a lot better then sindle-core systems. I do on occasion
> > do it with the kernel and can still continue using the system. (For
> > comparison, my desktop is a 4-core AMD64 with 8GB memory)
>
> Strange, in my case it was an i7 920 (4 cores, hyperthreaded, appears
> as 8 CPUs to Linux) with 12GB of RAM. Maybe if I prefixed it
> with"nice" it would not have brought my computer to its knees... or
> maybe related to the schedulers and other kernel voodoo that I don't
> understand. I might try it again someday :)

That is strange, unless your harddrive is really underperforming?
Or do you have all the options in the kernel selected?

Btw, HyperThreading doesn't work too well when you have a lot of identical 
tasks. In that case, you might end up with lesser performance as there are no 
"usable unused" parts in your cores, but the CPU-schedules (the hardware one 
for HT) is looking for things to fill those last few bits with.

--
Joost