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 ============= http://www.linux.codehelp.co.uk/
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