On Thu, 05 Apr 2007 19:42:19 +0200 [EMAIL PROTECTED] wrote: > Introduce a mechanism to wait on free memory. > > Currently congestion_wait() is abused to do this.
Such a very small explanation for such a terrifying change. > ... > > --- linux-2.6-mm.orig/mm/vmscan.c 2007-04-05 16:29:46.000000000 +0200 > +++ linux-2.6-mm/mm/vmscan.c 2007-04-05 16:29:49.000000000 +0200 > @@ -1436,6 +1436,7 @@ static int kswapd(void *p) > finish_wait(&pgdat->kswapd_wait, &wait); > > balance_pgdat(pgdat, order); > + page_alloc_ok(); > } > return 0; > } For a start, we don't know that kswapd freed pages which are in a suitable zone. And we don't know that kswapd freed pages which are in a suitable cpuset. congestion_wait() is similarly ignorant of the suitability of the pages, but the whole idea behind congestion_wait is that it will throttle page allocators to some speed which is proportional to the speed at which the IO systems can retire writes - view it as a variable-speed polling operation, in which the polling frequency goes up when the IO system gets faster. This patch changes that philosophy fundamentally. That's worth more than a 2-line changelog. Also, there might be situations in which kswapd gets stuck in some dark corner. Perhaps the process which is waiting in the page allocator holds filesystem locks which kswapd is blocked on. Or kswapd might be blocked on a particular request queue, or a dead NFS server or something. The timeout will save us, but things will be slow. There could be other problems too, dunno - this stuff is tricky. Why are you changing it, what problems are being solved, etc? - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
