On Thu, Apr 15, 2010 at 12:32:50PM +0800, KOSAKI Motohiro wrote: > > On Thu, Apr 15, 2010 at 11:31:52AM +0800, KOSAKI Motohiro wrote: > > > > > Many applications (this one and below) are stuck in > > > > > wait_on_page_writeback(). I guess this is why "heavy write to > > > > > irrelevant partition stalls the whole system". They are stuck on page > > > > > allocation. Your 512MB system memory is a bit tight, so reclaim > > > > > pressure is a bit high, which triggers the wait-on-writeback logic. > > > > > > > > I wonder if this hacking patch may help. > > > > > > > > When creating 300MB dirty file with dd, it is creating continuous > > > > region of hard-to-reclaim pages in the LRU list. priority can easily > > > > go low when irrelevant applications' direct reclaim run into these > > > > regions.. > > > > > > Sorry I'm confused not. can you please tell us more detail explanation? > > > Why did lumpy reclaim cause OOM? lumpy reclaim might cause > > > direct reclaim slow down. but IIUC it's not cause OOM because OOM is > > > only occur when priority-0 reclaim failure. > > > > No I'm not talking OOM. Nor lumpy reclaim. > > > > I mean the direct reclaim can get stuck for long time, when we do > > wait_on_page_writeback() on lumpy_reclaim=1. > > > > > IO get stcking also prevent priority reach to 0. > > > > Sure. But we can wait for IO a bit later -- after scanning 1/64 LRU > > (the below patch) instead of the current 1/1024. > > > > In Andreas' case, 512MB/1024 = 512KB, this is way too low comparing to > > the 22MB writeback pages. There can easily be a continuous range of > > 512KB dirty/writeback pages in the LRU, which will trigger the wait > > logic. > > In my feeling from your explanation, we need auto adjustment mechanism > instead change default value for special machine. no? You mean the dumb DEF_PRIORITY/2 may be too large for a 1TB memory box? However for such boxes, whether it be DEF_PRIORITY-2 or DEF_PRIORITY/2 shall be irrelevant: it's trivial anyway to reclaim an order-1 or order-2 page. In other word, lumpy_reclaim will hardly go 1. Do you think so? Thanks, Fengguang -- 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/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>