Re: [gentoo-user] Memory manager

[Dale]

Mick wrote:
> On Sunday, 20 October 2019 12:59:03 BST Wols Lists wrote:
>
>> Well, I do all my emerges on tmpfs, so if things like LO, firefox et al
>> need maybe 10GB, I need at least that available ... (that said, 16GB ram
>> could probably do it without needing swap :-)
> Anecdotal evidence suggests 16G RAM may not be enough:
>
> A number of times I was emerging chromium with USE="jumbo-build" enabled on a
> PC with 16G RAM, while a user was running Kmail, firefox and some other apps.
> FF in particular is a hog, as it pre-emptively allocates more RAM as you keep
> opening more tabs.  With 15-20 FF tabs open and MAKEOPTS="-j5", all RAM was
> exhausted and swap started being used heavily by portage, thrashing the disk
> as jobs were being swapped I/O.  With no swap the emerge would have been
> killed with an OOM.
>
>
>> But seeing as I try to fill up my mobo ram, my disks are mirrored, and I
>> still try and stick to the "twice ram" rule, this setup means any
>> upgrades/changes to the computer means I don't break that rule. If it's
>> overkill, well disk is cheap (and I can always nick a swap partition and
>> repurpose it temporarily if needs be :-)
>>
>> Cheers,
>> Wol
> Quite, disks are cheap and having more swap won't break the bank.  On PCs with
> limited RAM I often end up adding more swap space and reducing job counts to
> get big emerges through.
>


This is some things I've noticed.  I have swap but set it to not be used
unless something bad happens.  I think swappiness is set to like 10 or
20.  It's rare that any swap is ever used.  When it does, it is usually
some tab in Firefox that has went wild eating up memory.  Here's the
thing about using swap on my rig, once it does, the system gets
extremely slow.  Even switching desktops can take a minute or longer. 
Other than trying to get to what is eating up memory and killing it, the
system is virtually useless.  Even my video stops playing. 

For me and my experience, I only want swap available to prevent the
system from crashing and resetting itself.  It gives me a little time to
kill the memory hog and not have a crash.  Other than that, I don't want
swap used because it is just to slow.  I have 32GBs so it's rare that I
run out anymore.  When I had 16GBs tho, Firefox was a regular abuser. 
Seamonkey never runs wild exactly but sometimes I close and restart it
to force it to release memory.  What I wish, Firefox and even Seamonkey
would stop running wild with memory.  Sometimes it gets really hungry
and takes up several GBs when there is no reason to do so.

Like with Mick tho, 16GBs got to where it wasn't enough.  I had to close
web browsers during large compiles.  LOo, Firefox, Seamonkey etc etc.  I
have emerge's work directory on tmpfs here. 

That's my experience with swap, real world. 

Dale

:-)  :-)