Re: [gentoo-amd64] Re: upgrade an old system

[Sami Näätänen]

On Wednesday 06 May 2009 15:43:22 Mark Haney wrote:
> Volker Armin Hemmann wrote:
> > On Mittwoch 06 Mai 2009, Mark Haney wrote:
> >> Duncan wrote:
> >>> Consider pointing PORTAGE_TMPDIR at a tmpfs.
> >>>
> >>> The idea is based on the fact that everything portage does in its
> >>> tmpdir (/var/tmp by default) is temporary, erased as soon as it's done
> >>> emerging that package.  Since tmpfs uses swap backed memory,
> >>> worst-case, it has to write to swap -- that is, to disk, which is where
> >>> it would otherwise be writing ALL the temporary files.  With memory
> >>> access so much faster than disk access, every file that's erased before
> >>> it hits disk saves time, and it can make a BIG difference in emerge
> >>> times.
> >>
> >> Duncan, you talk about tmpfs and I'm suddenly interested in trying this
> >> out.  My question is, how much space do you allocate for the tmpfs?  I
> >> know it'll fall back to swap if I'm out of space there, but what works
> >> well for you?  I have (currently) 1GB RAM on this system, but I'm
> >> getting ready to order more to get me to 4GB.
> >
> > 2gb. That is enough for almost everything. Not enough for openoffice.
> > tmpfs                 2,0G  3,2M  2,0G   1% /var/tmp/portage
> > tmpfs                 1,0G  116K  1,0G   1% /tmp
>
> Now how is that going to play out when I only have 1GB of RAM?

IMHO You shouldn't use tmpfs for the PM temp dir, until you can give that 
around 2GB, which shouldn't be more than half of your total memory.

In your case there still could be some speed improvement if you have enough 
swap space. This because smaller packages wouldn't use disks at all, but still 
allowing bigger compiles to be carried out as the tmpfs would use swap when 
the memory starts to run low.


When I had only 2GB of memory I used a dedicated RAID 0 (striped) ext2fs 
partition for the PM temp dir. As in this use case the raw speed of the used 
FS is more important than the reliability.

Now I have 8GB of memory and I use 5GB and 2GB limits for the PM temp and the 
sys temp.