Re: Keeping mmap'ed files in core regression in 2.6.7-rc

[Nick Piggin <nickpiggin@yahoo.com.au>]

Andrew Morton wrote:
> Nick Piggin <nickpiggin@yahoo.com.au> wrote:
> 
>>Can you send the test app over?
> 
> 
> logical next step.
> 
> 
>>Andrew, do you have any ideas about how to fix this so far?
> 
> 
> Not sure what, if anything, is wrong yet.  It could be that reclaim is now
> doing the "right" thing, but this particular workload preferred the "wrong"
> thing.  Needs more investigation.
> 
> 
> 
>>>See how "cache" remains stable, but free/buffers memory is oscillating?
>>>That shouldn't happen, right ? 
>>>
>>
>>If it is doing IO to large regions of mapped memory, the page reclaim
>>can start getting a bit chunky. Not much you can do about it, but it
>>shouldn't do any harm.
> 
> 
> shrink_zone() will free arbitrarily large amounts of memory as the scanning
> priority increases.  Probably it shouldn't.
> 
> 

Especially for kswapd, I think, because it can end up fighting with
memory allocators and think it is getting into trouble. It should
probably rather just keep putting along quietly.

I have a few experimental patches that magnify this problem, so I'll
be looking at fixing it soon. The tricky part will be trying to
maintain a similar prev_priority / temp_priority balance.
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"aart@kvack.org"> aart@kvack.org </a>