thanks David
just added it to sysctl.conf at this commit:
http://qi-hw.com/p/openwrt-xburst/775a29c
On 01/15/2011 09:34 PM, David Kuehling wrote:
> Hi,
>
> currently the NanoNote comes with a setting of
> /proc/sys/vm/overcommit_memory = 0. This makes Linux' memory manager
> overly fussy with memory allocations, memory mappings and fork().
>
> The result is that large applications like Octave do not start due to
> missing memory, or sometimes a large application like Emacs is unable to
> execute a child process via fork() and exec() since the memory manager
> asseses that memory would not suffice to perform fork() on a huge
> process.
>
> In reality, memory mostly *does* suffice, though. It's just that there
> are more pages assigned to processes, than there is available RAM.
> Especially with large executables this is not a problem, since
> executables are mapped read-only from disk files to memory. If memory
> runs low, these read-only pages can just be dropped, and reloaded from
> disk whenever they are needed again.
>
> Setting /proc/sys/vm/overcommit_memory = 1 makes Linux memory manager
> more generous and allows processes to occupy more pages than there is
> RAM. The downside is, that applications then sometimes don't fail on
> calling malloc(), but instead segfault when they try to access pages
> that cannot be allocated to available RAM.
>
> In reality I've seen that the Linux OOM killer comes along and kills
> applications that it deems to memory hungry. I saw that behaviour with
> overcommit_memory set to 0 as well to 1, so I guess generally setting it
> to 1 won't make things much worse than they are already.
>
> So are you ok with such a change?
>
> The right place to change that setting would be from /etc/sysctl.conf.
> Should I add a sysctl.conf to data/qi_lb60/files/etc/ ?
>
> Would be nice to add it in a place that effects config.minimal as well
> as config.full_system. I want my config.minimal images to be able to
> run Octave out-of-the-box. BTW Octave consists of about 38MB of
> read-only library code that needs to be mapped. Of course depending on
> what you do, you won't actually use most of that code.
>
> cheers,
>
> David
>
> PS: some more info is available here:
> http://www.mjmwired.net/kernel/Documentation/sysctl/vm.txt
>
--
Best Regards
Xiangfu
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