Re: phk malloc, was (Re: ptmalloc2)
Christopher Weimann wrote:
> On 02/22/2005-11:33PM, Dan Melomedman wrote:
>
>>Another example could be 'dnscache'. It also preallocates the cache
>>database of user-configurable size at the start-up. It never writes
>>anywthing to the disk, and it doesn't need to, but I wouldn't want it
>>to crash because the OS won't have the physical memory it needs on
>>random basis.
>>
>
>
> One of the good things about dnscache is that it only allocates what you
> tell it to rather than growing forever like BIND. I think the key here
> is don't tell it to allocate more than you have and you won't ever have
> a problem.
You are misunderstanding the problem: malloc() returns non-NULL even
though the system cannot actually provide the memory. Applications
written to expect the possibility that malloc() can fail (good
programming practice) can still fail due to out-of-memory killing due to
overcommmit, even though they receive no indication that anything was
wrong (except the kill signal).
>
>
>>Let's stop here then. The feature I am looking for doesn't come with
>>Unix by default, beaten horse, etc.
>
>
> In the case of dnscache at least I don't think it is a feature you need.
>
Most UNIX systems will allow malloc() to return success even though the
memory is not available (that's what overcommit is).
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