On 2023/6/8 18:13, Mike Rapoport wrote: > On Thu, Jun 08, 2023 at 11:18:02AM +0200, Michal Hocko wrote: >> On Thu 08-06-23 15:38:48, Haifeng Xu wrote: >>> >>> >>> On 2023/6/7 18:22, David Hildenbrand wrote: >>>> On 07.06.23 12:16, Michal Hocko wrote: >>>>> On Wed 07-06-23 09:07:34, Haifeng Xu wrote: >>>>>> If freesize is less than dma_reserve, print warning message to report >>>>>> this case. >>>>> >>>>> Why? >>>> >>>> I'd like to second that question, and add >>>> >>>> a) Did you run into that scenario? >>>> b) What can an admin do in that case with that error messages? >>> >>> In theory，dma_reserve shouldn't exceed freesize, so the error messages can remind us >>> to verify whether the configuration of reserved memory is correct. >> >> I am not really convinced this is worth touching the code TBH. > > The only architecture that sets the dma_reserve is x86_64 and it sets it to > the number of reserved pages in DMA zone. There is no way freesize will be > less than dma_reserve. Yes. From the comments, x86_64 calculates the dma_reserve in order to set zone watermarks more accurately. But berfore init_per_zone_wmark_min(), memblock_free_all() has already recalculated the managed pages. It seems that the dma_reserve is not really helpful to this. > > I'm not sure that in general dma_reserve has some value now, but that's a > completely different story. > >> -- >> Michal Hocko >> SUSE Labs >
