On Fri, Dec 22, 2017 at 08:39:41AM +0530, Anshuman Khandual wrote: > On 12/14/2017 07:40 AM, Ross Zwisler wrote: <> > > We solve this issue by providing userspace with performance information on > > individual memory ranges. This performance information is exposed via > > sysfs: > > > > # grep . mem_tgt2/* mem_tgt2/local_init/* 2>/dev/null > > mem_tgt2/firmware_id:1 > > mem_tgt2/is_cached:0 > > mem_tgt2/local_init/read_bw_MBps:40960 > > mem_tgt2/local_init/read_lat_nsec:50 > > mem_tgt2/local_init/write_bw_MBps:40960 > > mem_tgt2/local_init/write_lat_nsec:50 <> > We will enlist properties for all possible "source --> target" on the system? Nope, just 'local' initiator/target pairs. I talk about the reasoning for this in the cover letter for patch 3: https://lists.01.org/pipermail/linux-nvdimm/2017-December/013574.html > Right now it shows only bandwidth and latency properties, can it accommodate > other properties as well in future ? We also have an 'is_cached' attribute for the memory targets if they are involved in a caching hierarchy, but right now those are all the things we expose. We can potentially expose whatever we want that is present in the HMAT, but those seemed like a good start. I noticed that in your presentation you had some other examples of attributes you cared about: * reliability * power consumption * density The HMAT doesn't provide this sort of information at present, but we could/would add them to sysfs if the HMAT ever grew support for them. > > This allows applications to easily find the memory that they want to use. > > We expect that the existing NUMA APIs will be enhanced to use this new > > information so that applications can continue to use them to select their > > desired memory. > > I had presented a proposal for NUMA redesign in the Plumbers Conference this > year where various memory devices with different kind of memory attributes > can be represented in the kernel and be used explicitly from the user space. > Here is the link to the proposal if you feel interested. The proposal is > very intrusive and also I dont have a RFC for it yet for discussion here. > > https://linuxplumbersconf.org/2017/ocw//system/presentations/4656/original/Hierarchical_NUMA_Design_Plumbers_2017.pdf > > Problem is, designing the sysfs interface for memory attribute detection > from user space without first thinking about redesigning the NUMA for > heterogeneous memory may not be a good idea. Will look into this further. I took another look at your presentation, and overall I think that if/when a NUMA redesign like this takes place ACPI systems with HMAT tables will be able to participate. But I think we are probably a ways away from that, and like I said in my previous mail ACPI systems with memory-only NUMA nodes are going to exist and need to be supported with the current NUMA scheme. Hence I don't think that this patch series conflicts with your proposal. -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
