Re: [gentoo-user] Re: aligning SSD partitions

[Dale]

Neil Bothwick wrote:
> On Thu, 06 Sep 2012 05:03:55 -0500, Dale wrote:
>
>>>> You miss this point not me.  I *cleared* that cache.  From
>>>> kernel.org:
>>> Sorry Dale, but you are missing the point. You cleared the cache
>>> before running emerge, then ran emerge. The first thing emerge did
>>> was unpack the tarball and populate the disk cache. All clearing the
>>> disk cache did was make sure there was plenty of space to cache the
>>> new data, thus speeding up the process.
>> Then explain to me why it was at times slower while on tmpfs?  Trust me,
>> I ran this test many times and in different orders and it did NOT make
>> much if any difference.
> So it was slower at times, but not by much? That's just general variances
> caused by multi-tasking, wind direction etc.

That's the point.  It doesn't make any difference whether you have
portages work directory on tmpfs or not.  For the point of this thread,
it would be a good idea to save wear and tear on the SSD but one should
NOT expect that emerge will compile packages any faster because of it
being on tmpfs instead of on disk.  I might also add, I ran some of my
tests in single user mode.  That is about as raw as Linux gets but there
is still the chance of variances here and there.  That's why I said not
much.  Sometimes one would be a second or two faster then next time be a
second or two slower.  Basically, just normal variances that may not be
related to one another. 

>
>> I might add, the cache on the drive I was using is nowhere near large
>> enough to cache the tarball for the package.  Heck, the cache on my
>> current system drive is only 8Mbs according to hdparm.
> We're not talking about drive caches, the kernel caches filesystem access
> long before it gets anywhere the drive. So all the real work is done in
> RAM if you have enough, whether you are using a hard drive filesystem or
> tmpfs. All your test demonstrates is that if you have enough RAM, it
> doesn't make much difference where you put PORTAGE_TMPDIR.
>
>

The command mentioned several replies back CLEARS that cache.  When you
run that command to clear the cache, from my understanding, at that
point it is as if the command has never been run since the last reboot. 
Meaning, the command, emerge in this case, and its children are NOT
cached in ram nor is anything else.  I posted that from kernel.org. 
That's their claim not mine.  If you don't accept that clearing the
cache works, you need to talk to the kernel people because they are
saying it there and I'm just repeating it here.  A link for you to read:

http://www.kernel.org/doc/Documentation/sysctl/vm.txt

Just scroll down to the section about drop_caches.  Read it for yourself
if you can't/won't accept me saying it. 

Dale

:-)  :-) 

-- 
I am only responsible for what I said ... Not for what you understood or how you interpreted my words!