> ... first thinking about redesigning the NUMA for > heterogeneous memory may not be a good idea. Will look into this further. I agree with comment that first a direction should be defined how to handle heterogeneous memory system. > https://linuxplumbersconf.org/2017/ocw//system/presentations/4656/original/ > Hierarchical_NUMA_Design_Plumbers_2017.pdf I miss in the presentation a user perspective of the new approach, e.g. - How does application developer see/understand the heterogeneous memory system? - How does app developer use the heterogeneous memory system? - What are modification in API/sys interfaces? In other hand, if we assume that separate memory NUMA node has different memory capabilities/attributes from stand point of particular CPU, it is easy to explain for user how to describe/handle heterogeneous memory. Of course, current numa design is not sufficient in kernel in following areas today: - Exposing memory attributes that describe heterogeneous memory system - Interfaces to use the heterogeneous memory system, e.g. more sophisticated policies - Internal mechanism in memory management, e.g. automigration, maybe something else. > -----Original Message----- > From: Anshuman Khandual [mailto:khandual@xxxxxxxxxxxxxxxxxx] > Sent: Friday, December 22, 2017 4:10 AM > To: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx > Cc: Anaczkowski, Lukasz <lukasz.anaczkowski@xxxxxxxxx>; Box, David E > <david.e.box@xxxxxxxxx>; Kogut, Jaroslaw <Jaroslaw.Kogut@xxxxxxxxx>; Koss, > Marcin <marcin.koss@xxxxxxxxx>; Koziej, Artur <artur.koziej@xxxxxxxxx>; > Lahtinen, Joonas <joonas.lahtinen@xxxxxxxxx>; Moore, Robert > <robert.moore@xxxxxxxxx>; Nachimuthu, Murugasamy > <murugasamy.nachimuthu@xxxxxxxxx>; Odzioba, Lukasz > <lukasz.odzioba@xxxxxxxxx>; Wysocki, Rafael J <rafael.j.wysocki@xxxxxxxxx>; > Rafael J. Wysocki <rjw@xxxxxxxxxxxxx>; Schmauss, Erik > <erik.schmauss@xxxxxxxxx>; Verma, Vishal L <vishal.l.verma@xxxxxxxxx>; > Zheng, Lv <lv.zheng@xxxxxxxxx>; Andrew Morton <akpm@linux- > foundation.org>; Balbir Singh <bsingharora@xxxxxxxxx>; Brice Goglin > <brice.goglin@xxxxxxxxx>; Williams, Dan J <dan.j.williams@xxxxxxxxx>; > Hansen, Dave <dave.hansen@xxxxxxxxx>; Jerome Glisse <jglisse@xxxxxxxxxx>; > John Hubbard <jhubbard@xxxxxxxxxx>; Len Brown <lenb@xxxxxxxxxx>; Tim > Chen <tim.c.chen@xxxxxxxxxxxxxxx>; devel@xxxxxxxxxx; linux- > acpi@xxxxxxxxxxxxxxx; linux-mm@xxxxxxxxx; linux-nvdimm@xxxxxxxxxxxx > Subject: Re: [PATCH v3 0/3] create sysfs representation of ACPI HMAT > > On 12/14/2017 07:40 AM, Ross Zwisler wrote: > > ==== Quick Summary ==== > > > > Platforms exist today which have multiple types of memory attached to > > a single CPU. These disparate memory ranges have some characteristics > > in common, such as CPU cache coherence, but they can have wide ranges > > of performance both in terms of latency and bandwidth. > > Right. > > > > > For example, consider a system that contains persistent memory, > > standard DDR memory and High Bandwidth Memory (HBM), all attached to > the same CPU. > > There could potentially be an order of magnitude or more difference in > > performance between the slowest and fastest memory attached to that CPU. > > Right. > > > > > With the current Linux code NUMA nodes are CPU-centric, so all the > > memory attached to a given CPU will be lumped into the same NUMA node. > > This makes it very difficult for userspace applications to understand > > the performance of different memory ranges on a given CPU. > > Right but that might require fundamental changes to the NUMA > representation. > Plugging those memory as separate NUMA nodes, identify them through sysfs > and try allocating from it through mbind() seems like a short term solution. > > Though if we decide to go in this direction, sysfs interface or something similar > is required to enumerate memory properties. > > > > > 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 > > I might have missed discussions from earlier versions, why we have this kind of > a "source --> target" model ? We will enlist properties for all possible "source -- > > target" on the system ? Right now it shows only bandwidth and latency > properties, can it accommodate other properties as well in future ? > > > > > 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. -------------------------------------------------------------------- Intel Technology Poland sp. z o.o. ul. Slowackiego 173 | 80-298 Gdansk | Sad Rejonowy Gdansk Polnoc | VII Wydzial Gospodarczy Krajowego Rejestru Sadowego - KRS 101882 | NIP 957-07-52-316 | Kapital zakladowy 200.000 PLN. Ta wiadomosc wraz z zalacznikami jest przeznaczona dla okreslonego adresata i moze zawierac informacje poufne. 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