On Mon, 19 Nov 2012 16:38:18 +0100 Marek Szyprowski m.szyprowski@samsung.com wrote:
Hello,
On 11/14/2012 11:58 PM, Andrew Morton wrote:
On Mon, 12 Nov 2012 09:59:42 +0100 Marek Szyprowski m.szyprowski@samsung.com wrote:
It has been observed that system tends to keep a lot of CMA free pages even in very high memory pressure use cases. The CMA fallback for movable pages is used very rarely, only when system is completely pruned from MOVABLE pages, what usually means that the out-of-memory even will be triggered very soon. To avoid such situation and make better use of CMA pages, a heuristics is introduced which turns on CMA fallback for movable pages when the real number of free pages (excluding CMA free pages) approaches low water mark.
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erk, this is right on the page allocator hotpath. Bad.
Yes, I know that it adds an overhead to allocation hot path, but I found no other place for such change. Do You have any suggestion where such change can be applied to avoid additional load on hot path?
Do the work somewhere else, not on a hot path? Somewhere on the page reclaim path sounds appropriate. How messy would it be to perform some sort of balancing at reclaim time?