Hi > > zone->all_unreclaimable and zone->pages_scanned are neigher atomic > > variables nor protected by lock. Therefore zones can become a state > > of zone->page_scanned=0 and zone->all_unreclaimable=1. In this case, > > current all_unreclaimable() return false even though > > zone->all_unreclaimabe=1. > > > > Is this ignorable minor issue? No. Unfortunatelly, x86 has very > > small dma zone and it become zone->all_unreclamble=1 easily. and > > if it become all_unreclaimable=1, it never restore all_unreclaimable=0. > > Why? if all_unreclaimable=1, vmscan only try DEF_PRIORITY reclaim and > > a-few-lru-pages>>DEF_PRIORITY always makes 0. that mean no page scan > > at all! > > > > Eventually, oom-killer never works on such systems. That said, we > > can't use zone->pages_scanned for this purpose. This patch restore > > all_unreclaimable() use zone->all_unreclaimable as old. and in addition, > > to add oom_killer_disabled check to avoid reintroduce the issue of > > commit d1908362. > > The above is a nice analysis of the bug and how it came to be > introduced. But we don't actually have a bug description! What was > the observeable problem which got fixed? The above says "Eventually, oom-killer never works". Is this no enough? The above says 1) current logic have a race 2) x86 increase a chance of the race by dma zone 3) if race is happen, oom killer don't work > > Such a description will help people understand the importance of the > patch and will help people (eg, distros) who are looking at a user's > bug report and wondering whether your patch will fix it. > -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>