Swap exhaustion

[Doug Hardie]

> On 27 May 2015, at 17:06, kpneal at pobox.com wrote:
> 
> On Wed, May 27, 2015 at 04:49:52PM -0700, Doug Hardie wrote:
>> I have a process that is eating up 6 GB of swap space.  At that point, FreeBSD 9.3 terminates a process.  However, occasionally its not the one eating up the space.  When I manually quit the process then the swap space returns to a few KB used.  The system runs fine after that.
>> 
>> I have very little knowledge of what this process is doing internally but would like to know what might be causing this issue.  There are 5 of these processes running (parent plus 4 children).  Normally each uses about 90 MB RES/SIZE.  However when the problem occurs they are about 2GB RES/SIZE each.  The system has 4 GB memory.  I thought that a malloc would not be able to grab that much memory, even with swapping as it has to be in memory.  Could a malloc cause this growth in process size or need I look elsewhere?
> 
> There's a difference between "real" memory and "virtual" memory. The
> malloc() call allocates _virtual_ memory. So the maximum amount that can be
> malloc'd and used would be the size of your real memory plus the size of
> your swap space.

If I am understanding correctly, then it appears that a process can actually allocate enough memory to eat up the swap space.  Then I need to find out why that process is allocating so much memory.  Thanks.