Eric Lee / linux-smarc-t335x-v3.2

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Commit 73ce02e96fe34a983199a9855b2ae738f960a6ee

Authored by KOSAKI Motohiro
Committed by Linus Torvalds
1 parent 594fe1a044
Exists in master and in 4 other branches v3.2_AM335xPSP_04.06.00.11, v3.2_NEWT335xPSP_04.06.00.11, v3.2_SBC_SMARTMEN, v3.2_SMARCT335xPSP_04.06.00.11

mm: stop kswapd's infinite loop at high order allocation 

Wassim Dagash reported following kswapd infinite loop problem.

  kswapd runs in some infinite loop trying to swap until order 10 of zone
  highmem is OK.... kswapd will continue to try to balance order 10 of zone
  highmem forever (or until someone release a very large chunk of highmem).

For non order-0 allocations, the system may never be balanced due to
fragmentation but kswapd should not infinitely loop as a result.

Instead, recheck all watermarks at order-0 as they are the most important.
If watermarks are ok, kswapd will go back to sleep.

[akpm@linux-foundation.org: fix comment]
Reported-by: wassim dagash <wassim.dagash@gmail.com>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Showing 1 changed file with 17 additions and 0 deletions Side-by-side Diff

... ... @@ -1867,6 +1867,23 @@
1867 1867  
1868 1868 try_to_freeze();
1869 1869  
  1870 + /*
  1871 + * Fragmentation may mean that the system cannot be
  1872 + * rebalanced for high-order allocations in all zones.
  1873 + * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX,
  1874 + * it means the zones have been fully scanned and are still
  1875 + * not balanced. For high-order allocations, there is
  1876 + * little point trying all over again as kswapd may
  1877 + * infinite loop.
  1878 + *
  1879 + * Instead, recheck all watermarks at order-0 as they
  1880 + * are the most important. If watermarks are ok, kswapd will go
  1881 + * back to sleep. High-order users can still perform direct
  1882 + * reclaim if they wish.
  1883 + */
  1884 + if (sc.nr_reclaimed < SWAP_CLUSTER_MAX)
  1885 + order = sc.order = 0;
  1886 +
1870 1887 goto loop_again;
1871 1888 }
1872 1889