Re: mlock(1)

[Jeff Garzik <jgarzik@pobox.com>]

Chris Wright wrote:
> * Alan Cox (alan@lxorguk.ukuu.org.uk) wrote:
> 
>>On Gwe, 2004-09-24 at 21:22, Chris Wright wrote:
>>
>>>Hard to say if it's a policy decision outside the scope of the app.
>>>Esp. if the app knows it needs to not be swapped.  Either something that
>>>has realtime needs, or more specifically, privacy needs.  Don't need to
>>>mlock all of gpg to ensure key data never hits swap.
>>
>>Keys are a different case anyway. We can swap them if we have encrypted
>>swap (hardware or software) and we could use the crypto lib just to
>>crypt some pages in swap although that might be complex. As such a
>>MAP_CRYPT seems better than mlock. If we don't have cryptable swap then
>>fine its mlock.
> 
> 
> Yeah, sounds nice.  This is still very much an app specific policy, not
> something that a helper such as mlock(1) would solve.

It's all app-specific policy.  mlock(1) allows the sysadmin to apply 
app-specific policy on top of whatever app-specific policy the engineer 
has chosen to hardcode into his app.

A smart sysadmin that knows the working set of his _local configuration_ 
of a given app is sometimes in a better position to make a decision 
about mlockall(2) than the engineer.

	Jeff