On Wed, Oct 12, 2022 at 5:34 AM Vinicius Petrucci <vpetrucci@xxxxxxxxx> wrote: > > > Well, per address range operation is a completely different beast I > > would say. External tool would need to a) understand what that range is > > used for (e.g. stack/heap ranges, mmaped shared files like libraries or > > private mappings) and b) by in sync with memory layout modifications > > done by applications (e.g. that an mmap has been issued to back malloc > > request). Quite a lot of understanding about the specific process. I > > would say that with that intimate knowledge it is quite better to be > > part of the process and do those changes from within of the process > > itself. > > Sorry, this may be a digression, but just wanted to mention a > particular use case from a project I recently collaborated on (to > appear next month at IIWSC 2022: > http://www.iiswc.org/iiswc2022/index.html). > > We carried out a performance analysis of the latest Linux AutoNUMA > memory tiering on graph processing applications. We noticed that hot > pages cannot be properly identified by the reactive approach used by > AutoNUMA due to irregular/random memory access patterns. Thus, as a > POC, we implemented and evaluated a simple idea of having an external > user-level process/agent that, based on prior profiling results of > memory regions, could make more effectively memory chunk/object-based > mappings (instead of page-level allocation/migration) in advance on > either DRAM or CXL/PMEM (via mbind calls). This kind of tiering > solution could deliver up to 2x more performance for graph analytics > workloads. We plan to evaluate other workloads as well. > > Having a feature like "pidfd/process_mbind" would really simplify our > user-level agent implementation moving forward, as right now we are > adding a LD_PRELOAD wrapper (for signal handler) to listen and execute > "mbind" requests from another process. If there's any other > alternative solution to this already (via ptrace?), please let me > know. > Interesting, looking forward to seeing your paper! This is the kind of use case I was trying to describe for pidfd_mbind() - a userspace orchestrator with some intimate knowledge of the process' memory layout (through profiling, like in your case, or otherwise), that can direct memory to the right nodes / memory tiers. - Frank
