Memory reserves or lack thereof

[Alan Cox]

On 11/12/2012 3:48 PM, Konstantin Belousov wrote:
> On Mon, Nov 12, 2012 at 01:28:02PM -0800, Sushanth Rai wrote:
>> This patch still doesn't address the issue of M_NOWAIT calls driving
>> the memory the all the way down to 2 pages, right ? It would be nice to
>> have M_NOWAIT just do non-sleep version of M_WAITOK and M_USE_RESERVE
>> flag to dig deep.
> This is out of scope of the change. But it is required for any further
> adjustements.

I would suggest a somewhat different response:

The patch does make M_NOWAIT into a "non-sleep version of M_WAITOK" and 
does reintroduce M_USE_RESERVE as a way to specify "dig deep".

Currently, both M_NOWAIT and M_WAITOK can drive the cache/free memory 
down to two pages.  The effect of the patch is to stop M_NOWAIT at two 
pages rather than allowing it to continue to zero pages.

When you say, "This is out of scope ...", I believe that you are 
referring to changing two pages into something larger.  I agree that 
this is out of scope for the current change.

Alan