On 20 Mar 2000 15:53:20 +0100, you wrote:
>Den 17-Mar-00 05:27:13 skrev Alan Cox følgende om "Re: Overcomittable memory":
>
>> You also need to pick a number to count as 'potentially kernel eaten' which
>> I guess for paranoia sake you'd pick ram size. This means you need to turn
>> it on after boot so you can actually set up swap to run anything.
>
> Not necessary. Just take into account the amount used by the kernel at
>the time of the allocation attemp. To the process asking for memory, it
>makes no difference who has already allocated memory on the system. All it
>needs to know is if it got it, and if so, where it is.
In other words, you leave the kernel allocating its own memory on
demand?
> In how many ways can a program allocate memory? The ones that come to my
>mind right now are (s)brk(), mmap(), fork(), exec() and stack. Are there
>more?
Or populating a sparse matrix in memory. How would you implement this
without overcommit/demand-allocation??
> The kernel reserves some memory for kernel use. For example the first
>number from /proc/sys/vm/freepages. Are there more cases? Perhaps a minimum
>number disk block buffer/cache pages?
Yes, it keeps odd chunks of RAM and VM free for itself. Not enough to
guarantee any arbitrary operation would succeed without allocating
more, though - and why should it?
James.
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This archive was generated by hypermail 2b29 : Thu Mar 23 2000 - 21:00:30 EST