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

[Michael Mol]

On Mon, Sep 10, 2012 at 7:13 AM, Dale <rdalek1967@×××××.com> wrote:

> Nicolas Sebrecht wrote:
> > The 07/09/12, Dale wrote:
> >
> >> The thing is tho, whether it is using the memory as cache or using it
> >> as
> >> tmpfs, it is the same memory.  There is no difference.  That's the
> >> whole
> >> point.
> > Feel free to take your own assumptions as undeniable truth. The way the
> > kernel work with memory is the key, of course.
> >
> > Now, as long as you blind yourself with statements like that, I'm not
> > going to respond anymore. I guess you need to make some basic research.
> >
>
> I understand how the kernel uses memory.  That's why it doesn't matter
> if you put portage's work directory on tmpfs or not.  I been using Linux
> for a pretty good long while now.  I have a pretty good understanding of
> it, especially the things that I use.
>
> Respond or not, I know what I tested and what the results were.  They
> were not just my tests and results either.
>

Nobody is disagreeing with your test results. In fact, they're not even
disagreeing with you that they mean what you think they mean within the
context you're testing. They're disagreeing with your extrapolation of your
results to other contexts. In short, all other things being equal, your
test results work out for someone in the exact same circumstances as
yourself...but there are a _lot_ of other things that need to be equal!

Filesystem mount options can have an impact. For example, let's say your
filesystem is configured to make writes synchronous, for general data
integrity purposes. That would slow PORTAGE_TMP down something _fierce_.

Someone might be tweaking any number of the knobs under 'vm' in /proc.
vm.swappiness, vm.dirty_* or vm.min_free_kbytes are ones that caught my
eye, but really most of them in there look relevant.

Or consider that someone else might be running drop_caches, or even sync()
while your code is running. (Heck, if there's a database, even an sqlite
database, on the same filesystem, that's almost a guarantee.)

These may seem to be obvious, but these are the kinds of things people were
trying to get you to be willing to acknowledge before you made blanket
assertions which covered them.

-- 
:wq