On Thu, Jul 26, 2018 at 04:20:39PM +0200, Michal Hocko wrote: > On Thu 26-07-18 06:01:06, Matthew Wilcox wrote: > > On Thu, Jul 26, 2018 at 03:22:02PM +0300, Mike Rapoport wrote: > > > +Memory Allocation Controls > > > +========================== > > > > Perhaps call this section "Memory Allocation Flags" instead? > > > > > +Linux provides a variety of APIs for memory allocation from direct > > > +calls to page allocator through slab caches and vmalloc to allocators > > > +of compressed memory. Although these allocators have different > > > +semantics and are used in different circumstances, they all share the > > > +GFP (get free page) flags that control behavior of each allocation > > > +request. > > > > While this isn't /wrong/, I think it might not be the most useful way > > of explaining what the GFP flags are to someone who's just come across > > them in some remote part of the kernel. How about this paragraph instead? > > > > Functions which need to allocate memory often use GFP flags to express > > how that memory should be allocated. The GFP acronym stands for "get > > free pages", the underlying memory allocation function. > > OK. > > > Not every GFP > > flag is allowed to every function which may allocate memory. Most > > users will want to use a plain ``GFP_KERNEL`` or ``GFP_ATOMIC``. > > Or rather than mentioning the two just use "Useful GFP flag > combinations" comment segment from gfp.h The comment there includes GFP_DMA, GFP_NOIO etc so I'd prefer Matthew's version and maybe even omit GFP_ATOMIC from it. Some grepping shows that roughly 80% of allocations are GFP_KERNEL, 12% are GFP_ATOMIC and ... I didn't count the usage of other flags ;-) > -- > Michal Hocko > SUSE Labs > -- Sincerely yours, Mike.
