Re: Total vs per-cpu memory
On Thu, Jan 31, 2008 at 09:12:52AM -0800, Francesco Pietra wrote:
> Hi Len:
> I agree. However, these are no standardized codes. Actually, it is a code in
> development that is faced with extreme situations that could not have been in
> the mind of the developer. Docking a large molecule onto a protein without bias
> is a challenging task, that the program accomplices nicely up to a certain size
> of the ligand. I am pushing the program beyond the limits for which it was
> devised. That "pushing" in order to tell where the program needs to be revised.
> The developer is not putting together known routines, he is inventing the way
> to come out.
Any time you see segmentation fault, the programmer made a mistake. The
situation is completely irrelevant. If you don't check return codes of
system calls then you made a mistake. Simple as that.
> That said, you are certainly able to answer my question about how RAM is used
> by a single cpu in my Tyan (all 8 sets of memory occupied) when the other cpus
> are dormant. If not, the only way I can invent is to look at top -i when the
> ligand is large but not so large to induce segmentation fault.
If it is a single system, then all ram is available in one big pool. If
it is an opteron then some ram will be faster for some CPUs (that being
whatever ram is connected directly is slightly faster than ram connected
to another CPU, but only slightly).
If you run 32bit programs, then you can have at most 3GB of ram as far
as I recall with linux. Certainly no more than 4GB. With a 64bit
programs you can allocate any amount of ram, as long as the system
still has any left and assuming there aren't any user limits applied
that could prevent you from allocating anymore.
--
Len Sorensen
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