On Mon, Dec 07, 2020 at 04:54:21PM -0800, Dan Williams wrote: > [ add perf maintainers ] > > On Sun, Nov 8, 2020 at 1:16 PM Vaibhav Jain <vaib...@linux.ibm.com> wrote: > > > > Implement support for exposing generic nvdimm statistics via newly > > introduced dimm-command ND_CMD_GET_STAT that can be handled by nvdimm > > command handler function and provide values for these statistics back > > to libnvdimm. Following generic nvdimm statistics are defined as an > > enumeration in 'uapi/ndctl.h': > > > > * "media_reads" : Number of media reads that have occurred since reboot. > > * "media_writes" : Number of media writes that have occurred since reboot. > > * "read_requests" : Number of read requests that have occurred since reboot. > > * "write_requests" : Number of write requests that have occurred since > > reboot. > > Perhaps document these as "since device reset"? As I can imagine some > devices might have a mechanism to reset the count outside of "reboot" > which is a bit ambiguous. > > > * "total_media_reads" : Total number of media reads that have occurred. > > * "total_media_writes" : Total number of media writes that have occurred. > > * "total_read_requests" : Total number of read requests that have occurred. > > * "total_write_requests" : Total number of write requests that have > > occurred. > > > > Apart from ND_CMD_GET_STAT ioctl these nvdimm statistics are also > > exposed via sysfs '<nvdimm-device>/stats' directory for easy user-space > > access like below: > > > > /sys/class/nd/ndctl0/device/nmem0/stats # tail -n +1 * > > ==> media_reads <== > > 252197707602 > > ==> media_writes <== > > 20684685172 > > ==> read_requests <== > > 658810924962 > > ==> write_requests <== > > 404464081574 > > Hmm, I haven't looked but how hard would it be to plumb these to be > perf counter-events. So someone could combine these with other perf > counters? > > > In case a specific nvdimm-statistic is not supported than nvdimm > > command handler function can simply return an error (e.g -ENOENT) for > > request to read that nvdimm-statistic. > > Makes sense, but I expect the perf route also has a way to enumerate > which statistics / counters are supported. I'm not opposed to also > having them in sysfs, but I think perf support should be a first class > citizen.
arch/x86/events/msr.c might be a good starting point for a software pmu delivering pure counters.