mm/vmscan: Maintain TLB coherency in LRU code #6358
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As a workaround (and possibly a fix) for CPU spins observed on BCM2837, use ptep_clear_flush_young instead of ptep_test_and_clear_young inside lru_gen_look_around in order to expose PTE changes to the MMU. Note that on architectures that don't require an explicit flush, ptep_clear_flush_young just calls ptep_test_and_clear_young. Signed-off-by: Phil Elwell <phil@raspberrypi.com>
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There is a mailing-list discussion about this issue: https://marc.info/?l=linux-mm&m=172614610701899&w=2 |
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A timelapse camera test which is known to trigger the CPU spins has now reached 3000 frames in 5 hours without any significant slowdown (a monitoring application reported an unexpected 3 second delay, but there is no clear gap in the timestamps). |
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kernel: mm/vmscan: Maintain TLB coherency in LRU code See: raspberrypi/linux#6358
popcornmix
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kernel: mm/vmscan: Maintain TLB coherency in LRU code See: raspberrypi/linux#6358
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As a workaround (and possibly a fix) for CPU spins observed on BCM2837, use ptep_clear_flush_young instead of ptep_test_and_clear_young inside lru_gen_look_around in order to expose PTE changes to the MMU. Note that on architectures that don't require an explicit flush, ptep_clear_flush_young just calls ptep_test_and_clear_young.