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Re: severity for bugs in ignoring TMP/TMPDIR?

On Thu, 9 Feb 2012 17:22:58 +0100
Salvo Tomaselli <tiposchi@tiscali.it> wrote:

> In data Tuesday 07 February 2012 17:39:46, bastien ROUCARIES ha scritto:
> > And swap as hell and kill interactivity
> i am afraid many people on this list have no direct experience of what happens 
> when linux is out of memory and starts to swap.

... on something other than a fast hard disk ...

Swapping isn't a problem on a desktop or reasonably modern laptop (it's
arguably an indicator of other problems on a server) because it's
usually fast enough that the user won't notice.

Swapping - if it's even enabled - on embedded devices with solid state
storage really isn't fun because writing data is just so slow.
> i have an embedded system with 32MiB of RAM where no matter how large the swap 
> partition is, going out of memory causes some programs to crash

... usually with a SIGABORT which is very, very unkind to the data
being handled by the process at that time ...

>, or sometimes 
> leads to strange behaviour of programs being "running", doing nothing and 
> impossible to kill. And in these cases an hard reboot is the only solution.

32Mb is a very small amount of RAM though - we've been doing OK in
128Mb (with no swap support) but got into problems with fork|exec
because that effectively cuts your RAM in half - or fails. We found a
fix for that (the blame eventually lay in pango) and we also try to
avoid fork|exec inside processes which need a lot of RAM. It's more
manageable to use something like dbus, sockets or other IPC and have
two processes each using 30% of RAM (or less) than one taking 60%.

To fit into very small amounts of RAM, you have to be able to
restructure the code and that, generally, means cross-building modified
packages. One day, once Multi-Arch is fully implemented, Emdebian will
restart work on that area.

I'd be surprised if you're able to use eglibc in 32Mb of RAM though -
I wonder if you've considered rebuilding for uClibc or similar. Mind
you, once you get into that area, you wonder if the final system is
actually recognisably Debian anymore...


Neil Williams

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