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Jaewon Kim authored
Using order 4 pages would be helpful for IOMMUs mapping, but trying to get order 4 pages could spend quite much time in the page allocation. From the perspective of responsiveness, the deterministic memory allocation speed, I think, is quite important. The order 4 allocation with __GFP_RECLAIM may spend much time in reclaim and compation logic. __GFP_NORETRY also may affect. These cause unpredictable delay. To get reasonable allocation speed from dma-buf system heap, use HIGH_ORDER_GFP for order 4 to avoid reclaim. And let me remove meaningless __GFP_COMP for order 0. According to my tests, order 4 with MID_ORDER_GFP could get more number of order 4 pages but the elapsed times could be very slow. time order 8 order 4 order 0 584 usec 0 160 0 28,428 usec 0 160 0 100,701 usec 0 160 0 76,645 usec 0 160 0 25,522 usec 0 160 0 38,798 usec 0 160 0 89,012 usec 0 160 0 23,015 usec 0 160 0 73,360 usec 0 160 0 76,953 usec 0 160 0 31,492 usec 0 160 0 75,889 usec 0 160 0 84,551 usec 0 160 0 84,352 usec 0 160 0 57,103 usec 0 160 0 93,452 usec 0 160 0 If HIGH_ORDER_GFP is used for order 4, the number of order 4 could be decreased but the elapsed time results were quite stable and fast enough. time order 8 order 4 order 0 1,356 usec 0 155 80 1,901 usec 0 11 2384 1,912 usec 0 0 2560 1,911 usec 0 0 2560 1,884 usec 0 0 2560 1,577 usec 0 0 2560 1,366 usec 0 0 2560 1,711 usec 0 0 2560 1,635 usec 0 28 2112 544 usec 10 0 0 633 usec 2 128 0 848 usec 0 160 0 729 usec 0 160 0 1,000 usec 0 160 0 1,358 usec 0 160 0 2,638 usec 0 31 2064 Link: https://lkml.kernel.org/r/20230303050332.10138-1-jaewon31.kim@samsung.comSigned-off-by:
Jaewon Kim <jaewon31.kim@samsung.com> Reviewed-by:
John Stultz <jstultz@google.com> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@kernel.org> Cc: Sumit Semwal <sumit.semwal@linaro.org> Cc: T.J. Mercier <tjmercier@google.com> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org>
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