On Sat 08-07-17 13:59:54, Tetsuo Handa wrote: [...] > Quoting from http://lkml.kernel.org/r/20170705081956.GA14538@xxxxxxxxxxxxxx : > Michal Hocko wrote: > > On Sat 01-07-17 20:43:56, Tetsuo Handa wrote: > > > You are rejecting serialization under OOM without giving a chance to test > > > side effects of serialization under OOM at linux-next.git. I call such attitude > > > "speculation" which you never accept. > > > > No I am rejecting abusing the lock for purpose it is not aimed for. > > Then, why adding a new lock (not oom_lock but warn_alloc_lock) is not acceptable? > Since warn_alloc_lock is aimed for avoiding messages by warn_alloc() getting > jumbled, there should be no reason you reject this lock. > > If you don't like locks, can you instead accept below one? No, seriously! Just think about what you are proposing. You are stalling and now you will stall _random_ tasks even more. Some of them for unbound amount of time because of inherent unfairness of cmpxchg. If there is a _real_ problem it should be debugged and fixed. If this is a limitation of what printk can handle then we should think how to throttle it even more (e.g. does it make much sense to dump_stack when it hasn't changed since the last time?). If this is about dump_stack taking too long then we should look into it but we definitely should add a more on top. > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 80e4adb..3ac382c 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -3900,9 +3900,14 @@ bool gfp_pfmemalloc_allowed(gfp_t gfp_mask) > > /* Make sure we know about allocations which stall for too long */ > if (time_after(jiffies, alloc_start + stall_timeout)) { > + static bool wait; > + > + while (cmpxchg(&wait, false, true)) > + schedule_timeout_uninterruptible(1); > warn_alloc(gfp_mask & ~__GFP_NOWARN, ac->nodemask, > "page allocation stalls for %ums, order:%u", > jiffies_to_msecs(jiffies-alloc_start), order); > + wait = false; > stall_timeout += 10 * HZ; > } > -- Michal Hocko SUSE Labs -- 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/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
