Bug#280871: Problems with apache, PHP, MM and UML.
On Sat, Nov 13, 2004 at 02:58:55AM +1000, Adam Conrad wrote:
> Mark: Can you think of any reason why forcing MMFILE might lead to the
> symptoms described in the two bug reports CCd?
Well, the MMFILE implementation is a mmapped file. This will cause it
to allocate backing store for the shared memory segment when it is used.
If this is only showing up on UML systems my first guess would be that
sending the process a signal (as a configuration reload does) causes the
UML kernel to allocate backing store for the entire memory mapping.
Otherwise the reload probably just causes PHP to walk over the entire
shared memoy segment.
I'd guess that the old build would've been using System V shared memory
which wouldn't have the backing store - it could be figured out readily
although the mirror I use doesn't seem to have the old stable mm binary
package and I managed to loose my archive a while ago. If it had ended
up doing that then there would be no such issues with backing store.
MMFILE was chosen because it's the most conservative mechanism in terms
of kernel compatibility and when System V shared memory did get used it
caused problems for PHP since the default system limit on shared memory
is 32Mb with 2.6 kernels - PHP tries to allocate 64Mb and fails.
--
"You grabbed my hand and we fell into it, like a daydream - or a fever."
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