64 bit Dual-Core Moron

Sorry, I meant to go to the list.



---------- Forwarded message ----------
From: David Fox <dfox94085@xxxxxxxxx>
Date: Fri, Aug 1, 2008 at 12:34 PM
Subject: Re: 64 bit Dual-Core Moron
To: Account for Debian group mail <debian@xxxxxxxx>


On Fri, Aug 1, 2008 at 11:58 AM, Account for Debian group mail
<debian@xxxxxxxx> wrote:
I looks like both CPUs are doing their thing on the kernel compile. Here
is a quick look at the top info:

Are you doing a plain make or make -j 2 or something else?

The thing is, if you just do a 'make' then one core is mostly going to
be used by the compiler, and the other core might be used for all the
other processes. I just tried it myself. I was looking at top output
and there were plenty of times where one or the other of the cpus were
essentially idle.

Since (I assume) you have a dual core cpu, then each of those cpus may
be able to hyperthread, so you might do a make -j 4.

Here's what I see (just a snapshot of top). I have other cpu-intensive
things running, like setiathome.



Tasks: 170 total, 8 running, 161 sleeping, 0 stopped, 1 zombie
Cpu0 : 89.4%us, 8.9%sy, 1.7%ni, 0.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
Cpu1 : 87.3%us, 11.3%sy, 0.0%ni, 0.3%id, 0.0%wa, 0.7%hi, 0.3%si, 0.0%st
Mem: 1932840k total, 1468592k used, 464248k free, 12336k buffers
Swap: 1951888k total, 40244k used, 1911644k free, 740692k cached

I see you have twice the RAM as I do. If you just do a make (or make
-j 4) your compiler processes are only using up a small portion of the
RAM. How do you go about making sure all that ram is being exercised?
That was my point. (Oh, and the system crashed my X session when I did
a make -j 128 on kernel 2.6.25.9 - chosen roughly at random.)

I noticed while I was compiling with plain 'make' that the memory was
hardly used, most of it was in free (over a gigabyte, with no X server
running) and it slowly drew memory from free and put it into buffers,
so that the cc1 process could be reloaded from there rather than from
disk, I guess. But it (cc1) never really ever used up more than 64
megs (and that's probably a generous upper limit for kernel compiles)
and presumably it was working on that same 64 meg area, although with
VM there's no way to tell.


--
To UNSUBSCRIBE, email to debian-user-REQUEST@xxxxxxxxxxxxxxxx
with a subject of "unsubscribe". Trouble? Contact listmaster@xxxxxxxxxxxxxxxx

Relevant Pages

  • Re: Invoking External Batch Program on Multiple Core Machine
    ... (Although free version of command line .NET compiler is available, so if some new feature would greatly ... work (you pass it a file in the command line, it runs for 2-45 minutes and spits out another file). ... This is very annoying since I have a dual core machine and would like to get my work done as quickly as possible. ... You can use the Process class to start a new process with a specific command, and you can even set the ProcessorAffinity on the class instance to control what CPUs it runs on. ...
    (microsoft.public.dotnet.languages.csharp)
  • Re: A chip too far? Where is your solution Mr Larkin?
    ... 100 MB RAM ... that same version of Slackware Linux on a 8-processor Xeon box ... Smaller-faster smaller-faster smaller-faster. ... The PBCC version compiler and IDE are ...
    (sci.electronics.design)
  • Re: [OT] Re: Whats the name for this?
    ... I need to point out that the older CPUs ... > step from the earlier dedicated computing devices. ... > in cases where the programmers themselves are more comfortable in a CISC ... > who programs with no knowledge of how a compiler works. ...
    (comp.programming)
  • Re: "Insufficient virtual memory" error message in Linux
    ... 4GB of ram and linux redhat. ... to address the memory, hence it can handle at most 4GB of ram ... (Last I knew the Watcom compiler would generate large model 32 bit ... PAE is a lot of work for the user program. ...
    (comp.lang.fortran)
  • Re: code optimization in embedded systems
    ... is the correct advice? ... better compiler. ... of the data (eg. char on 8/16-bit but int on 32-bit CPUs). ... efficient initialization of global variables at startup when possible. ...
    (comp.arch.embedded)