On Mon 19-04-21 18:37:13, Christian König wrote: > Am 19.04.21 um 18:11 schrieb Michal Hocko: [...] > > The question is not whether it is NUMA aware but whether it is useful to > > know per-numa data for the purpose the counter is supposed to serve. > > No, not at all. The pages of a single DMA-buf could even be from different > NUMA nodes if the exporting driver decides that this is somehow useful. As the use of the counter hasn't been explained yet I can only speculate. One thing that I can imagine to be useful is to fill gaps in our accounting. It is quite often that the memroy accounted in /proc/meminfo (or oom report) doesn't add up to the overall memory usage. In some workloads the workload can be huge! In many cases there are other means to find out additional memory by a subsystem specific interfaces (e.g. networking buffers). I do assume that dma-buf is just one of those and the counter can fill the said gap at least partially for some workloads. That is definitely useful. What I am trying to bring up with NUMA side is that the same problem can happen on per-node basis. Let's say that some user consumes unexpectedly large amount of dma-buf on a certain node. This can lead to observable performance impact on anybody on allocating from that node and even worse cause an OOM for node bound consumers. How do I find out that it was dma-buf that has caused the problem? See where I am heading? -- Michal Hocko SUSE Labs
