Re: [gentoo-amd64] Re: Symlinks vs. Bind mounts.

[Beso]

2008/8/12 Morgan Wesström <gentoo-amd64@×××××××××.biz>

> Duncan wrote:
>
>> Now, if you /really/ want to make a difference in portage's speed,
>> consider pointing PORTAGE_TMPDIR at a tmpfs.  If you've a decent amount of
>> memory, it'll make a HUGE difference, since all the files it normally
>> creates only temporarily in by default, /var/tmp/portage/* will be created
>> in memory (tmpfs) only.  Even with a relatively low amount of memory, say a
>> gig (we're talking amd64 system context here, after all, and a gig has been
>> relatively common since its introduction, not some old 1990s 32-bit x86),
>> where tmpfs may be swapped out in some cases, the shortest lived files
>> should never hit disk (swap in the case of tmpfs) at all.  That's a LOT of
>> extreme-latency hard-disk I/O avoided!!  If you have some serious memory, 2
>> gig, 4 gig, higher (I have 8 gig), it's even MORE effective, as only the
>> biggest merges will ever hit disk at all, except of course for the initial
>> PORTDIR/DISTDIR operations and the final qmerge to the live filesystem.
>>
>
> This advice caught my attention since I moved my tmp space to Reiserfs for
> performance reasons. My knowledge of tmpfs is limited but I think it is a
> filesystem that uses RAM and can grow and shrink dynamically, right? If I
> follow this advice, what happens when I compile something like Open Office
> which allocates 3-4GB in /var/tmp during compilation and I only have 2GB
> physical RAM in the computer?
>

you'll use swap partition. but you'll not allocate all that ram space with
openoffice. i've tried to compile it twice. first time it was on disk and it
took almost 14 hours of compilation. the second time was on tmpfs with 3.8gb
and a 6gb swap file and it took less than 8 hours and i've never filled the
swap partition. to put at maximum use this method with low ram then don't
start xorg and graphical terminals but only the base vt and compile from
there. this will save you quite some ram space. you'll also find that the -j
option in your make.conf could be increased much when going with tmpfs. for
example i've passed from -j5 in hd use to -j9 in tmpfs and i still have a
very good and usable graphical system. with the old single core pc i was
using -j2 in hd and -j5 on tmpfs. this dramattically decreases compilation
time.

@duncan: do you remember that some time ago you were speaking about posting
the scripts to compile the kernel with the make.conf optimizations, but you
haven't posted them any more. do you still use them?!

-- 
dott. ing. beso