On Fri, 18 Mar 2022 09:29:20 +0100 David Hildenbrand <david@xxxxxxxxxx> wrote: > On 18.03.22 06:13, xhao@xxxxxxxxxxxxxxxxx wrote: > > > > On 3/18/22 12:42 AM, David Hildenbrand wrote: > >> On 17.03.22 08:03, Xin Hao wrote: > >>> Hi David, > >>> > >>> On 3/16/22 11:09 PM, David Hildenbrand wrote: > >>>> On 15.03.22 17:37, Xin Hao wrote: > >>>> > >>>> s/minotor/monitor/ > >>> Thanks, i will fix it. > >>>>> The purpose of these patches is to add CMA memory monitoring function. > >>>>> In some memory tight scenarios, it will be a good choice to release more > >>>>> memory by monitoring the CMA memory. > >>>> I'm sorry, but it's hard to figure out what the target use case should > >>>> be. Who will release CMA memory and how? Who will monitor that? What are > >>>> the "some memory tight scenarios"? What's the overall design goal? > >>> I may not be describing exactly what i mean，My intention is to find out > >>> how much of the reserved CMA space is actually used and which is unused, > >>> For those that are not used, I understand that they can be released by > >>> cma_release(). Of course, This is just a little personal thought that I > >>> think is helpful for saving memory. > >> Hm, not quite. We can place movable allocations on cma areas, to be > >> migrated away once required for allocations via CMA. So just looking at > >> the pages allocated within a CMA area doesn't really tell you what's > >> actually going on. > > > > I don't think so, the damon not looking at the pages allocate, It is > > constantly monitoring who is using CMA area pages through tracking page > > access bit > > > > in the kernel via the kdamond.x thread, So through damon, it can tell us > > about the hot and cold distribution of CMA memory. > > I'm not sure I follow. With random movable pages being placed on the CMA > area, the mentioned use case of "cma_release()" to release pages doesn't > make sense to me. > > I assume I'm missing the big picture -- and that should be properly > documented in the patch description. We don't add stuff just because it > could be used somehow, there should be a clear motivation how it can > actually be used. Same opinion from my side. The purpose and usage of this patch is unclear to me. Could you please clarify more, Xin? Thanks, SJ > > -- > Thanks, > > David / dhildenb
