On Sat, 24 Mar 2012 13:03:53 +1100 Anton Blanchard <anton@xxxxxxxxx> wrote: > I booted the latest git today on a ppc64 box. When I pushed it into > swap I noticed both kswapd's were using 100% CPU and the soft lockup > detector suggested it was stuck in balance_pgdat: > > BUG: soft lockup - CPU#7 stuck for 23s! [kswapd1:359] > Call Trace: > [c00000000015e190] .balance_pgdat+0x150/0x940 > [c00000000015eb2c] .kswapd+0x1ac/0x490 > [c00000000009edbc] .kthread+0xbc/0xd0 > [c00000000002142c] .kernel_thread+0x54/0x70 Are you running without CONFIG_COMPACTION enabled by any chance? Because if you do, the stub function compaction_suitable will always return COMPACT_SKIPPED: > I haven't had time to bisect but I did notice we were looping here: > > +++ b/mm/vmscan.c > @@ -2945,9 +2959,11 @@ out: > if (zone->all_unreclaimable && priority != DEF_PRIORITY) > continue; > > +#if 0 > /* Would compaction fail due to lack of free memory? */ > if (compaction_suitable(zone, order) == COMPACT_SKIPPED) > goto loop_again; > +#endif The patch below should fix it. ----- Only test compaction_suitable if the kernel is built with CONFIG_COMPACTION, otherwise the stub compaction_suitable function will always return COMPACT_SKIPPED and send kswapd into an infinite loop. Signed-off-by: Rik van Riel <riel@xxxxxxxxxx> Reported-by: Anton Blanchard <anton@xxxxxxxxx> diff --git a/mm/vmscan.c b/mm/vmscan.c index 7658fd6..33c332b 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2946,7 +2946,8 @@ out: continue; /* Would compaction fail due to lack of free memory? */ - if (compaction_suitable(zone, order) == COMPACT_SKIPPED) + if (COMPACTION_BUILD && + compaction_suitable(zone, order) == COMPACT_SKIPPED) goto loop_again; /* Confirm the zone is balanced for order-0 */ -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>