On Tue, Apr 26, 2011 at 02:29:15PM +0800, Dave Young wrote: > On Tue, Apr 26, 2011 at 2:25 PM, Wu Fengguang <fengguang.wu@xxxxxxxxx> wrote: > > On Tue, Apr 26, 2011 at 02:07:17PM +0800, Dave Young wrote: > >> On Tue, Apr 26, 2011 at 2:05 PM, Dave Young <hidave.darkstar@xxxxxxxxx> wrote: > >> > On Tue, Apr 26, 2011 at 1:55 PM, Wu Fengguang <fengguang.wu@xxxxxxxxx> wrote: > >> >> On Tue, Apr 26, 2011 at 01:49:25PM +0800, Dave Young wrote: > >> >>> Hi, > >> >>> > >> >>> When memory pressure is high, readahead could cause oom killing. > >> >>> IMHO we should stop readaheading under such circumstancesãIf it's true > >> >>> how to fix it? > >> >> > >> >> Good question. Before OOM there will be readahead thrashings, which > >> >> can be addressed by this patch: > >> >> > >> >> http://lkml.org/lkml/2010/2/2/229 > >> > > >> > Hi, I'm not clear about the patch, could be regard as below cases? > >> > 1) readahead alloc fail due to low memory such as other large allocation > >> > >> For example vm balloon allocate lots of memory, then readahead could > >> fail immediately and then oom > > > > If true, that would be the problem of vm balloon. It's not good to > > consume lots of memory all of a sudden, which will likely impact lots > > of kernel subsystems. > > > > btw readahead page allocations are completely optional. They are OK to > > fail and in theory shall not trigger OOM on themselves. We may > > consider passing __GFP_NORETRY for readahead page allocations. > > Good idea, care to submit a patch? Here it is :) Thanks, Fengguang --- readahead: readahead page allocations is OK to fail Pass __GFP_NORETRY for readahead page allocations. readahead page allocations are completely optional. They are OK to fail and in particular shall not trigger OOM on themselves. Reported-by: Dave Young <hidave.darkstar@xxxxxxxxx> Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx> --- include/linux/pagemap.h | 5 +++++ mm/readahead.c | 2 +- 2 files changed, 6 insertions(+), 1 deletion(-) --- linux-next.orig/include/linux/pagemap.h 2011-04-26 14:27:46.000000000 +0800 +++ linux-next/include/linux/pagemap.h 2011-04-26 14:29:31.000000000 +0800 @@ -219,6 +219,11 @@ static inline struct page *page_cache_al return __page_cache_alloc(mapping_gfp_mask(x)|__GFP_COLD); } +static inline struct page *page_cache_alloc_cold_noretry(struct address_space *x) +{ + return __page_cache_alloc(mapping_gfp_mask(x)|__GFP_COLD|__GFP_NORETRY); +} + typedef int filler_t(void *, struct page *); extern struct page * find_get_page(struct address_space *mapping, --- linux-next.orig/mm/readahead.c 2011-04-26 14:27:02.000000000 +0800 +++ linux-next/mm/readahead.c 2011-04-26 14:27:24.000000000 +0800 @@ -180,7 +180,7 @@ __do_page_cache_readahead(struct address if (page) continue; - page = page_cache_alloc_cold(mapping); + page = page_cache_alloc_cold_noretry(mapping); if (!page) break; page->index = page_offset; -- 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>