| Message ID | cover.1647378112.git.xhao@linux.alibaba.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | mm/damon: Add CMA minotor support | expand |
On 15.03.22 17:37, Xin Hao wrote: s/minotor/monitor/ > 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?
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. >
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.
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. --cc SeongJae Park <sj@kernel.org> More about damon, you can refer to this link：https://sjp38.github.io/post/damon/ <https://sjp38.github.io/post/damon/> >
On 18.03.22 06:13, xhao@linux.alibaba.com 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.
On Fri, 18 Mar 2022 09:29:20 +0100 David Hildenbrand <david@redhat.com> wrote: > On 18.03.22 06:13, xhao@linux.alibaba.com 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