On Thu, May 12, 2011 at 05:04:41PM -0500, James Bottomley wrote: > On Thu, 2011-05-12 at 15:04 -0500, James Bottomley wrote: > > Confirmed, I'm afraid ... I can trigger the problem with all three > > patches under PREEMPT. It's not a hang this time, it's just kswapd > > taking 100% system time on 1 CPU and it won't calm down after I unload > > the system. > > Just on a "if you don't know what's wrong poke about and see" basis, I > sliced out all the complex logic in sleeping_prematurely() and, as far > as I can tell, it cures the problem behaviour. I've loaded up the > system, and taken the tar load generator through three runs without > producing a spinning kswapd (this is PREEMPT). I'll try with a > non-PREEMPT kernel shortly. > > What this seems to say is that there's a problem with the complex logic > in sleeping_prematurely(). I'm pretty sure hacking up > sleeping_prematurely() just to dump all the calculations is the wrong > thing to do, but perhaps someone can see what the right thing is ... I think I see the problem: the boolean logic of sleeping_prematurely() is odd. If it returns true, kswapd will keep running. So if pgdat_balanced() returns true, kswapd should go to sleep. This? diff --git a/mm/vmscan.c b/mm/vmscan.c index 2b701e0..092d773 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2261,7 +2261,7 @@ static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining, * must be balanced */ if (order) - return pgdat_balanced(pgdat, balanced, classzone_idx); + return !pgdat_balanced(pgdat, balanced, classzone_idx); else return !all_zones_ok; } -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx 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>