On Fri, Oct 02, 2020 at 09:11:23AM +0200, Michal Hocko wrote: > On Thu 01-10-20 21:26:26, Uladzislau Rezki wrote: > > > > > > No, I meant going back to idea of new gfp flag, but adjust the implementation in > > > the allocator (different from what you posted in previous version) so that it > > > only looks at the flag after it tries to allocate from pcplist and finds out > > > it's empty. So, no inventing of new page allocator entry points or checks such > > > as the one you wrote above, but adding the new gfp flag in a way that it doesn't > > > affect existing fast paths. > > > > > OK. Now i see. Please have a look below at the patch, so we fully understand > > each other. If that is something that is close to your view or not: > > > > <snip> > > t a/include/linux/gfp.h b/include/linux/gfp.h > > index c603237e006c..7e613560a502 100644 > > --- a/include/linux/gfp.h > > +++ b/include/linux/gfp.h > > @@ -39,8 +39,9 @@ struct vm_area_struct; > > #define ___GFP_HARDWALL 0x100000u > > #define ___GFP_THISNODE 0x200000u > > #define ___GFP_ACCOUNT 0x400000u > > +#define ___GFP_NO_LOCKS 0x800000u > > Even if a new gfp flag gains a sufficient traction and support I am > _strongly_ opposed against consuming another flag for that. Bit space is > limited. That is definitely true. I'm not happy with the GFP flag at all, the comment is at best a damage limiting move. It still would be better for a memory pool to be reserved and sized for critical allocations. > Besides that we certainly do not want to allow craziness like > __GFP_NO_LOCK | __GFP_RECLAIM (and similar), do we? That would deserve to be taken to a dumpster and set on fire. The flag combination could be checked in the allocator but the allocator path fast paths are bad enough already. -- Mel Gorman SUSE Labs
