On Thu, 2011-07-28 at 09:15 +0800, Andrew Morton wrote: > 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. oh, I missed the code size will increase, so it's not good then. > 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. looks it should be per task, as reclaim could sleep. either putting it to task_struct or allocating it, both are not good. Thanks, Shaohua -- 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>