Hi David,
>>>Look in mm/mmap.c and search for overcommit_memory, then do same
>>>in the sources for your redhat kernels.
>>I'll look into RH kernel to see if it isn't like you say :-)
>>>Perhaps there's a patch for it floating around somewhere? ;-)
>>Now, that would be really nice.
>>Though I have no idea of where to look!?
> Here is what I do. Patch is against BK linuxppc-2.4 version 1.1285
> (2.4.28-pre3) but might work.
Well, the patch goes straight into my 2.4.20 ppc-kernel - but we have to
wait until tomorrow to see if it does the magic.
> Burns 5% of the RAM but alternatives all seem worse and I never
I can live with that (3%)...
> If you find out why RH works it would be interesting ... perhaps
> there is a better way.
I downloaded the 2.4.20-10 kernel SRPM from RH8 - it contains all the
patches they apply to the serene 2.4.20 kernel.
There is some stuff regarding introducing the
"overcommit_memory_accounting" variable from the 2.5 kernel, but I
haven't looked into it in depth.
I'll try with your patch first :-)
BR,
Martin Egholm
> #
> # mm/mmap.c
> # Add pessimistic overcommit mode similar to 2.6 mode 2.
> # This allows malloc aka sbrk() to actually fail before
> # process is killed.
> # Overloaded sysctl_overcommit_memory to be both enable
> # and ratio to avoid making a new sysctl.
> #
> diff -Nru a/mm/mmap.c b/mm/mmap.c
> --- a/mm/mmap.c 2005-03-30 07:15:13 -08:00
> +++ b/mm/mmap.c 2005-03-30 07:15:13 -08:00
> @@ -45,9 +45,13 @@
> __S000, __S001, __S010, __S011, __S100, __S101, __S110, __S111
> };
>
> -int sysctl_overcommit_memory;
> +int sysctl_overcommit_memory = 98;
> +
> int max_map_count = DEFAULT_MAX_MAP_COUNT;
>
> +extern unsigned long totalram_pages;
> +extern unsigned long totalhigh_pages;
> +
> /* Check that a process has enough memory to allocate a
> * new virtual mapping.
> */
> @@ -66,7 +70,7 @@
> unsigned long free;
>
> /* Sometimes we want to use more memory than we have. */
> - if (sysctl_overcommit_memory)
> + if (sysctl_overcommit_memory == 1)
> return 1;
>
> /* The page cache contains buffer pages these days.. */
> @@ -91,7 +95,20 @@
> free += (dentry_stat.nr_unused * sizeof(struct dentry)) >>
> PAGE_SHIFT;
> free += (inodes_stat.nr_unused * sizeof(struct inode)) >>
> PAGE_SHIFT;
>
> + /*
> + * Leave the last 3% for root
> + */
> + if (current->euid)
> + free -= free / 32;
> +
> + /* Strict mode do not allocate last bit of memory */
> + if (sysctl_overcommit_memory) {
> + pages += (totalram_pages - totalhigh_pages)
> + * (100 - sysctl_overcommit_memory) / 100;
> + }
> +
> return free > pages;
> +
> }
>
> /* Remove one vm structure from the inode's i_mapping address space. */
>
>
>
