On Fri, 24 Jul 2020 12:04:02 +0900 Joonsoo Kim <js1304@xxxxxxxxx> wrote: > 2020년 7월 24일 (금) 오전 11:36, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>님이 작성: > > > > On Fri, 24 Jul 2020 11:23:52 +0900 Joonsoo Kim <js1304@xxxxxxxxx> wrote: > > > > > > > Second, clearing __GFP_MOVABLE in current_gfp_context() has a side effect > > > > > to exclude the memory on the ZONE_MOVABLE for allocation target. > > > > > > > > More whoops. > > > > > > > > Could we please have a description of the end-user-visible effects of > > > > this change? Very much needed when proposing a -stable backport, I think. > > > > > > In fact, there is no noticeable end-user-visible effect since the fallback would > > > cover the problematic case. It's mentioned in the commit description. Perhap, > > > performance would be improved due to reduced retry and more available memory > > > (we can use ZONE_MOVABLE with this patch) but it would be neglectable. > > > > > > > d7fefcc8de9147c is over a year old. Why did we only just discover > > > > this? This makes one wonder how serious those end-user-visible effects > > > > are? > > > > > > As mentioned above, there is no visible problem to the end-user. > > > > OK, thanks. In that case, I don't believe that a stable backport is > > appropriate? > > > > (Documentation/process/stable-kernel-rules.rst) > > Thanks for the pointer! > > Hmm... I'm not sure the correct way to handle this patch. I thought that > memalloc_nocma_{save,restore} is an API that is callable from the module. > If it is true, it's better to regard this patch as the stable candidate since > out-of-tree modules could use it without the fallback and it would cause > a problem. But, yes, there is no visible problem to the end-user, at least, > within the mainline so it is possibly not a stable candidate. > > Please share your opinion about this situation. We tend not to care much about out-of-tree modules. I don't think a theoretical concern for out-of-tree code justifies risking the stability of -stable kernels.