Re: [patch 0/9] Critical Mempools

From: Sridhar Samudrala
Date: Fri Jan 27 2006 - 03:32:46 EST


Benjamin LaHaise wrote:
On Thu, Jan 26, 2006 at 03:32:14PM -0800, Matthew Dobson wrote:
I thought the earlier __GFP_CRITICAL was a good idea.
Well, I certainly could have used that feedback a month ago! ;) The
general response to that patchset was overwhelmingly negative. Yours is
the first vote in favor of that approach, that I'm aware of.

Personally, I'm more in favour of a proper reservation system. mempools are pretty inefficient. Reservations have useful properties, too -- one could reserve memory for a critical process to use, but allow the system to use that memory for easy to reclaim caches or to help with memory defragmentation (more free pages really helps the buddy allocator).

Gfp flag? Better memory reclaim functionality?
Well, I've got patches that implement the GFP flag approach, but as I
mentioned above, that was poorly received. Better memory reclaim is a
broad and general approach that I agree is useful, but will not necessarily
solve the same set of problems (though it would likely lessen the severity
somewhat).

Which areas are the priorities for getting this functionality into? Networking over particular sockets? A GFP_ flag would plug into the current network stack trivially, as sockets already have a field to store the memory allocation flags.
Yes, i have posted patches that use this exact approach last month that use a critical page pool with
GFP_CRITICAL flag.
http://lkml.org/lkml/2005/12/14/65
http://lkml.org/lkml/2005/12/14/66

Thanks
Sridhar

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