Virtual memory consumption (both user and kernel) in modern CURRENT

[Giorgos Keramidas]

On 2006-02-16 12:35, Brian Candler <B.Candler at pobox.com> wrote:
>On Wed, Feb 15, 2006 at 11:11:49AM +0800, David Xu wrote:
>>>1) Is it normal that virtual memory size for almost every non-kernel
>>>process
>>>   is close to 50Mb now:
>>>
>>>    ftp://external.atlantis.dp.ua/FreeBSD/CURRENT/top.txt
>>>
>>>   Is it miscalculation or real growth of virtual address space?
>>
>> I believe this is the new malloc code in libc, I am seeing this on my
>> Athlon64 machine, now it likes swap memory, in the old days, it seldom
>> touched it.
>
> IIRR, the new malloc grabs 32MB immediately. However, I'd hope that doesn't
> mean that 32MB of pages are actually touched, and then get swapped out to
> disk. If it does, I'm staying on FreeBSD 6.0 :-)

I don't think so.

At least, not unless you are using the debugging features of malloc(),
which can result in all pages getting touched (i.e. if the "J" option is
enabled, to set all newly-allocated bytes to 0xa5, which is very helpful
when trying to catch accesses to uninitialized pointers).

It's all a matter of what you are prepared to trade-off and why, I guess :)