From: Dan Williams <dan.j.williams@intel.com>
To: Yang Shi <yang.shi@linux.alibaba.com>
Cc: Michal Hocko <mhocko@suse.com>,
Mel Gorman <mgorman@techsingularity.net>,
Rik van Riel <riel@surriel.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Andrew Morton <akpm@linux-foundation.org>,
Dave Hansen <dave.hansen@intel.com>,
Keith Busch <keith.busch@intel.com>,
Fengguang Wu <fengguang.wu@intel.com>,
"Du, Fan" <fan.du@intel.com>,
"Huang, Ying" <ying.huang@intel.com>,
Linux MM <linux-mm@kvack.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Vishal L Verma <vishal.l.verma@intel.com>
Subject: Re: [PATCH 01/10] mm: control memory placement by nodemask for two tier main memory
Date: Mon, 25 Mar 2019 16:18:04 -0700 [thread overview]
Message-ID: <CAPcyv4g3xzuS8hP9jOX_BXWyFEH32YfCEDs3a_K_VRODfATc=Q@mail.gmail.com> (raw)
In-Reply-To: <688dffbc-2adc-005d-223e-fe488be8c5fc@linux.alibaba.com>
On Mon, Mar 25, 2019 at 12:28 PM Yang Shi <yang.shi@linux.alibaba.com> wrote:
>
>
>
> On 3/23/19 10:21 AM, Dan Williams wrote:
> > On Fri, Mar 22, 2019 at 9:45 PM Yang Shi <yang.shi@linux.alibaba.com> wrote:
> >> When running applications on the machine with NVDIMM as NUMA node, the
> >> memory allocation may end up on NVDIMM node. This may result in silent
> >> performance degradation and regression due to the difference of hardware
> >> property.
> >>
> >> DRAM first should be obeyed to prevent from surprising regression. Any
> >> non-DRAM nodes should be excluded from default allocation. Use nodemask
> >> to control the memory placement. Introduce def_alloc_nodemask which has
> >> DRAM nodes set only. Any non-DRAM allocation should be specified by
> >> NUMA policy explicitly.
> >>
> >> In the future we may be able to extract the memory charasteristics from
> >> HMAT or other source to build up the default allocation nodemask.
> >> However, just distinguish DRAM and PMEM (non-DRAM) nodes by SRAT flag
> >> for the time being.
> >>
> >> Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
> >> ---
> >> arch/x86/mm/numa.c | 1 +
> >> drivers/acpi/numa.c | 8 ++++++++
> >> include/linux/mmzone.h | 3 +++
> >> mm/page_alloc.c | 18 ++++++++++++++++--
> >> 4 files changed, 28 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c
> >> index dfb6c4d..d9e0ca4 100644
> >> --- a/arch/x86/mm/numa.c
> >> +++ b/arch/x86/mm/numa.c
> >> @@ -626,6 +626,7 @@ static int __init numa_init(int (*init_func)(void))
> >> nodes_clear(numa_nodes_parsed);
> >> nodes_clear(node_possible_map);
> >> nodes_clear(node_online_map);
> >> + nodes_clear(def_alloc_nodemask);
> >> memset(&numa_meminfo, 0, sizeof(numa_meminfo));
> >> WARN_ON(memblock_set_node(0, ULLONG_MAX, &memblock.memory,
> >> MAX_NUMNODES));
> >> diff --git a/drivers/acpi/numa.c b/drivers/acpi/numa.c
> >> index 867f6e3..79dfedf 100644
> >> --- a/drivers/acpi/numa.c
> >> +++ b/drivers/acpi/numa.c
> >> @@ -296,6 +296,14 @@ void __init acpi_numa_slit_init(struct acpi_table_slit *slit)
> >> goto out_err_bad_srat;
> >> }
> >>
> >> + /*
> >> + * Non volatile memory is excluded from zonelist by default.
> >> + * Only regular DRAM nodes are set in default allocation node
> >> + * mask.
> >> + */
> >> + if (!(ma->flags & ACPI_SRAT_MEM_NON_VOLATILE))
> >> + node_set(node, def_alloc_nodemask);
> > Hmm, no, I don't think we should do this. Especially considering
> > current generation NVDIMMs are energy backed DRAM there is no
> > performance difference that should be assumed by the non-volatile
> > flag.
>
> Actually, here I would like to initialize a node mask for default
> allocation. Memory allocation should not end up on any nodes excluded by
> this node mask unless they are specified by mempolicy.
>
> We may have a few different ways or criteria to initialize the node
> mask, for example, we can read from HMAT (when HMAT is ready in the
> future), and we definitely could have non-DRAM nodes set if they have no
> performance difference (I'm supposed you mean NVDIMM-F or HBM).
>
> As long as there are different tiers, distinguished by performance, for
> main memory, IMHO, there should be a defined default allocation node
> mask to control the memory placement no matter where we get the information.
I understand the intent, but I don't think the kernel should have such
a hardline policy by default. However, it would be worthwhile
mechanism and policy to consider for the dax-hotplug userspace
tooling. I.e. arrange for a given device-dax instance to be onlined,
but set the policy to require explicit opt-in by numa binding for it
to be an allocation / migration option.
I added Vishal to the cc who is looking into such policy tooling.
> But, for now we haven't had such information ready for such use yet, so
> the SRAT flag might be a choice.
>
> >
> > Why isn't default SLIT distance sufficient for ensuring a DRAM-first
> > default policy?
>
> "DRAM-first" may sound ambiguous, actually I mean "DRAM only by
> default". SLIT should just can tell us what node is local what node is
> remote, but can't tell us the performance difference.
I think it's a useful semantic, but let's leave the selection of that
policy to an explicit userspace decision.
next prev parent reply other threads:[~2019-03-25 23:18 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-23 4:44 [RFC PATCH 0/10] Another Approach to Use PMEM as NUMA Node Yang Shi
2019-03-23 4:44 ` [PATCH 01/10] mm: control memory placement by nodemask for two tier main memory Yang Shi
2019-03-23 17:21 ` Dan Williams
2019-03-25 19:28 ` Yang Shi
2019-03-25 23:18 ` Dan Williams [this message]
2019-03-25 23:36 ` Yang Shi
2019-03-25 23:42 ` Dan Williams
2019-03-23 4:44 ` [PATCH 02/10] mm: mempolicy: introduce MPOL_HYBRID policy Yang Shi
2019-03-23 4:44 ` [PATCH 03/10] mm: mempolicy: promote page to DRAM for MPOL_HYBRID Yang Shi
2019-03-23 4:44 ` [PATCH 04/10] mm: numa: promote pages to DRAM when it is accessed twice Yang Shi
2019-03-29 0:31 ` kbuild test robot
2019-03-23 4:44 ` [PATCH 05/10] mm: page_alloc: make find_next_best_node could skip DRAM node Yang Shi
2019-03-23 4:44 ` [PATCH 06/10] mm: vmscan: demote anon DRAM pages to PMEM node Yang Shi
2019-03-23 6:03 ` Zi Yan
2019-03-25 21:49 ` Yang Shi
2019-03-24 22:20 ` Keith Busch
2019-03-25 19:49 ` Yang Shi
2019-03-27 0:35 ` Keith Busch
2019-03-27 3:41 ` Yang Shi
2019-03-27 13:08 ` Keith Busch
2019-03-27 17:00 ` Zi Yan
2019-03-27 17:05 ` Dave Hansen
2019-03-27 17:48 ` Zi Yan
2019-03-27 18:00 ` Dave Hansen
2019-03-27 20:37 ` Zi Yan
2019-03-27 20:42 ` Dave Hansen
2019-03-28 21:59 ` Yang Shi
2019-03-28 22:45 ` Keith Busch
2019-03-23 4:44 ` [PATCH 07/10] mm: vmscan: add page demotion counter Yang Shi
2019-03-23 4:44 ` [PATCH 08/10] mm: numa: add page promotion counter Yang Shi
2019-03-23 4:44 ` [PATCH 09/10] doc: add description for MPOL_HYBRID mode Yang Shi
2019-03-23 4:44 ` [PATCH 10/10] doc: elaborate the PMEM allocation rule Yang Shi
2019-03-25 16:15 ` [RFC PATCH 0/10] Another Approach to Use PMEM as NUMA Node Brice Goglin
2019-03-25 16:56 ` Dan Williams
2019-03-25 17:45 ` Brice Goglin
2019-03-25 19:29 ` Dan Williams
2019-03-25 23:09 ` Brice Goglin
2019-03-25 23:37 ` Dan Williams
2019-03-26 12:19 ` Jonathan Cameron
2019-03-25 20:04 ` Yang Shi
2019-03-26 13:58 ` Michal Hocko
2019-03-26 18:33 ` Yang Shi
2019-03-26 18:37 ` Michal Hocko
2019-03-27 2:58 ` Yang Shi
2019-03-27 9:01 ` Michal Hocko
2019-03-27 17:34 ` Dan Williams
2019-03-27 18:59 ` Yang Shi
2019-03-27 20:09 ` Michal Hocko
2019-03-28 2:09 ` Yang Shi
2019-03-28 6:58 ` Michal Hocko
2019-03-28 18:58 ` Yang Shi
2019-03-28 19:12 ` Michal Hocko
2019-03-28 19:40 ` Yang Shi
2019-03-28 20:40 ` Michal Hocko
2019-03-28 8:21 ` Dan Williams
2019-03-27 20:14 ` Dave Hansen
2019-03-27 20:35 ` Matthew Wilcox
2019-03-27 20:40 ` Dave Hansen
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