Re: confused about performance
A Dijous 14 Juny 2007 16:32, Lennart Sorensen va escriure:
> On Thu, Jun 14, 2007 at 04:08:54PM +0200, Leopold Palomo-Avellaneda wrote:
> > really, reading you makes me doubt about the whole port. How many apps do
> > we have in the debian pool that can win some kind of performance?
>
> If nothing else, running a 64bit kernel with 32bit user space is an
> option. That gives you support for more than 4GB ram without the
> penalty of PAE, but leaves user space limited to 3GB per process. I run
> one system that way and it runs great. Systems with that much ram are
> starting to be very common.
the question is how many apps need this quantity of ram? Also, the mobo have
to support that. My old mobo I think that it's limited to 4Gb.
> And as I said anything using floating point will benefit quite a bit.
> gcc will hopefully also get better at optimizing for the amd64
> architecture over time.
with this are you saying that all the apps that do some kind of operation with
doubles and floats will be better?
[....]
> I guess the real question then is: Does the benefits for those programs
> give enough to warrent a tiny loss on many smaller utilities? Running
> mixed 32/64bit on one system is just a pain, so in my book the trade off
> is worth it. I don't think I will notice the 1 or 2% potential loss due
> to the larger pointers, while I probably will notice the benefits of
> faster floating point (perl uses lots of floating point by the way) and
> direct access to more ram in larger programs.
sure, but I don't think that you have a loss, that I think that it's difficult
to me to undertand.
> Now I just tried a small stupid test here:
>
> I have a zip file that is 61592222 bytes. I tried running
> 'time tar cvzf test.tgz my.zip' on both 32 and 64 bit on an Athlon 64 3500+
> running a 64bit kernel with 1GB ram.
>
> According to time, it takes 0m3.776s of user time (so not counting
> system calls) on 64bit, and 0m4.556s on 32bit. That indicates tar/gzip
> runs 20% faster on 64bit than 32bit at least when the kernel is 64bit
> and run on the same machine. I ran them a few times each to make sure
> caching and such didn't affect them. Maybe your test method wasn't
> correct or the two systems aren't as identical as you think.
it doesn't worsewhile but thanks for the example, is very appropriate.
Leo
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