On Thu, 28 Jul 2011 09:04:20 +0800 Shaohua Li <shaohua.li@xxxxxxxxx> wrote: > > Using an additional 44 bytes of stack on that path is also > > significant(ly bad). But we need to fix that problem anyway. One way > > we could improve things in mm/vmscan.c is to move the blk_plug into > > scan_control then get the scan_control off the stack in some manner. > > That's easy for kswapd: allocate one scan_control per kswapd at > > startup. Doing it for direct-reclaim would be a bit trickier... > unfortunately, the direct-reclaim case is what cares about stack. > > BTW, the scan_control can be dieted. may_unmap/may_swap/may_writepage > can be a bit. swappiness < 100, so can be a char. order <= 11, can be a > char. should I do it to cut the size? All five will fit in a 32-bit word, at some expense in code size. But I think first it would be better to work on a way of getting it all off the stack, along with the blk_plug. Could be done with a per-cpu array and CPU pinning, but CPU pinning is a bit expensive nowadays. Could put a scan_control* into the tack_struct, but that's dopey. -- 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>