Andrew Lutomirski <luto@xxxxxxx> writes: [Putting the Intel graphics driver developers in cc.] > I'm back :-/ > > I just triggered the kswapd bug on 2.6.39.1, which has the > cond_resched in shrink_slab. This time my system's still usable (I'm > tying this email on it), but kswapd0 is taking 100% cpu. It *does* > schedule (tested by setting its affinity the same as another CPU hog > and confirming that each one gets 50%). > > It appears to be calling i915_gem_inactive_shrink in a loop. I have > probes on entry and return of i915_gem_inactive_shrink and on return > of shrink_slab. I see: > > kswapd0 47 [000] 59599.956573: mm_vmscan_kswapd_wake: nid=0 order=0 > kswapd0 47 [000] 59599.956575: shrink_zone: > (ffffffff810c848c) priority=12 zone=ffff8801005fe000 > kswapd0 47 [000] 59599.956576: shrink_zone_return: > (ffffffff810c848c <- ffffffff810c96c6) arg1=0 > kswapd0 47 [000] 59599.956578: i915_gem_inactive_shrink: > (ffffffffa0081e48) gfp_mask=d0 nr_to_scan=0 > kswapd0 47 [000] 59599.956589: shrink_return: > (ffffffffa0081e48 <- ffffffff810c6a62) arg1=320 > kswapd0 47 [000] 59599.956589: shrink_slab_return: > (ffffffff810c69f5 <- ffffffff810c96ec) arg1=0 > kswapd0 47 [000] 59599.956592: i915_gem_inactive_shrink: > (ffffffffa0081e48) gfp_mask=d0 nr_to_scan=0 > kswapd0 47 [000] 59599.956602: shrink_return: > (ffffffffa0081e48 <- ffffffff810c6a62) arg1=320 > kswapd0 47 [000] 59599.956603: shrink_slab_return: > (ffffffff810c69f5 <- ffffffff810c96ec) arg1=0 > kswapd0 47 [000] 59599.956605: shrink_zone: > (ffffffff810c848c) priority=12 zone=ffff8801005fee00 > kswapd0 47 [000] 59599.956606: shrink_zone_return: > (ffffffff810c848c <- ffffffff810c96c6) arg1=0 > kswapd0 47 [000] 59599.956608: i915_gem_inactive_shrink: > (ffffffffa0081e48) gfp_mask=d0 nr_to_scan=0 > kswapd0 47 [000] 59599.956609: shrink_return: > (ffffffffa0081e48 <- ffffffff810c6a62) arg1=0 > kswapd0 47 [000] 59599.956610: shrink_slab_return: > (ffffffff810c69f5 <- ffffffff810c96ec) arg1=0 > kswapd0 47 [000] 59599.956611: mm_vmscan_kswapd_wake: nid=0 order=0 > kswapd0 47 [000] 59599.956612: shrink_zone: > (ffffffff810c848c) priority=12 zone=ffff8801005fe000 > kswapd0 47 [000] 59599.956614: shrink_zone_return: > (ffffffff810c848c <- ffffffff810c96c6) arg1=0 > kswapd0 47 [000] 59599.956616: i915_gem_inactive_shrink: > (ffffffffa0081e48) gfp_mask=d0 nr_to_scan=0 > kswapd0 47 [000] 59599.956617: shrink_return: > (ffffffffa0081e48 <- ffffffff810c6a62) arg1=0 > kswapd0 47 [000] 59599.956618: shrink_slab_return: > (ffffffff810c69f5 <- ffffffff810c96ec) arg1=0 > kswapd0 47 [000] 59599.956620: i915_gem_inactive_shrink: > (ffffffffa0081e48) gfp_mask=d0 nr_to_scan=0 > kswapd0 47 [000] 59599.956621: shrink_return: > (ffffffffa0081e48 <- ffffffff810c6a62) arg1=0 > kswapd0 47 [000] 59599.956621: shrink_slab_return: > (ffffffff810c69f5 <- ffffffff810c96ec) arg1=0 > kswapd0 47 [000] 59599.956623: shrink_zone: > (ffffffff810c848c) priority=12 zone=ffff8801005fee00 > kswapd0 47 [000] 59599.956624: shrink_zone_return: > (ffffffff810c848c <- ffffffff810c96c6) arg1=0 > kswapd0 47 [000] 59599.956626: i915_gem_inactive_shrink: > (ffffffffa0081e48) gfp_mask=d0 nr_to_scan=0 > kswapd0 47 [000] 59599.956627: shrink_return: > (ffffffffa0081e48 <- ffffffff810c6a62) arg1=0 > kswapd0 47 [000] 59599.956628: shrink_slab_return: > (ffffffff810c69f5 <- ffffffff810c96ec) arg1=0 > kswapd0 47 [000] 59599.956629: mm_vmscan_kswapd_wake: nid=0 order=0 > > The command was: > > perf record -g -aR -p 47 -e probe:i915_gem_inactive_shrink -e > probe:shrink_return -e probe:shrink_slab_return -e probe:shrink_zone > -e probe:shrink_zone_return -e probe:kswapd_try_to_sleep -e > vmscan:mm_vmscan_kswapd_sleep -e vmscan:mm_vmscan_kswapd_wake -e > vmscan:mm_vmscan_wakeup_kswapd -e vmscan:mm_vmscan_lru_shrink_inactive > -e probe:wakeup_kswapd; perf script > > (shrink_return is i915_gem_inactive_shrink's return. sorry, badly named.) > > It looks like something kswapd_try_to_sleep is not getting called. > > I do not know how to reproduce this, but I'll leave it running overnight. > > --Andy > > -- > 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> > -- ak@xxxxxxxxxxxxxxx -- Speaking for myself only -- 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>