On Mon, 27 Sep 2010 11:17:19 +0900 (JST) KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> wrote: > > > > @@ -72,7 +72,7 @@ struct vm_area_struct; > > > > /* This equals 0, but use constants in case they ever change */ > > > > #define GFP_NOWAIT (GFP_ATOMIC & ~__GFP_HIGH) > > > > /* GFP_ATOMIC means both !wait (__GFP_WAIT not set) and use emergency pool */ > > > > -#define GFP_ATOMIC (__GFP_HIGH) > > > > +#define GFP_ATOMIC (__GFP_HIGH | __GFP_NOWARN) > > > > #define GFP_NOIO (__GFP_WAIT) > > > > #define GFP_NOFS (__GFP_WAIT | __GFP_IO) > > > > #define GFP_KERNEL (__GFP_WAIT | __GFP_IO | __GFP_FS) > > > > > > A much finer-tuned implementation would be to add __GFP_NOWARN just to > > > the networking call sites. I asked about this in June and it got > > > nixed: > > > > > > http://www.spinics.net/lists/netdev/msg131965.html > > > -- > > > > Yes, I remember this particular report was useful to find and correct a > > bug. > > > > I dont know what to say. > > > > Being silent or verbose, it really depends on the context ? > > At least, MM developers don't want to track network allocation failure > issue. We don't have enough knowledge in this area. To be honest, We > are unhappy current bad S/N bug report rate ;) > > Traditionally, We hoped this warnings help to debug VM issue. Well, no, not really. I thought that the main reason for having that warning was to debug _callers_ of the memory allocator. Firstly it tells us when callsites are being too optimistic: asking for large amounts of contiguous pages, sometimes from atomic context. Quite a number of such callsites have been fixed as a result. Secondly, memory allocation failures are a rare event, so the calling code's error paths are not well tested. This warning turns the bug report "hey, my computer locked up" into the much better "hey, I got this error message and then my computer locked up". This allows us to go and look at the offending code and see if it is handling ENOMEM correctly. However I don't recall this scenario ever having actually happened. > but > It haven't happen. We haven't detect VM issue from this allocation > failure report. Instead, We've received a lot of network allocation > failure report. > > Recently, The S/N ratio became more bad. If the network device enable > jumbo frame feature, order-2 GFP_ATOMIC allocation is called frequently. > Anybody don't have to assume order-2 allocation can success anytime. > > I'm not against accurate warning at all. but I cant tolerate this > semi-random warning steal our time. If anyone will not make accurate > warning, I hope to remove this one completely instead. We can disable the warning for only net drivers quite easily. I don't have any strong opinions, really - yes, we get quite a few such bug reports but most of them end up in my lap anyway and it can't be more than one per week, shrug. -- 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>