From: "Huang\, Ying" <ying.huang@intel.com>
To: Dave Hansen <dave.hansen@linux.intel.com>
Cc: <linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>,
<yang.shi@linux.alibaba.com>, <rientjes@google.com>,
<dan.j.williams@intel.com>
Subject: Re: [RFC][PATCH 8/8] mm/numa: new reclaim mode to enable reclaim-based migration
Date: Tue, 30 Jun 2020 15:23:53 +0800 [thread overview]
Message-ID: <87v9j9ow3a.fsf@yhuang-dev.intel.com> (raw)
In-Reply-To: <20200629234517.A7EC4BD3@viggo.jf.intel.com> (Dave Hansen's message of "Mon, 29 Jun 2020 16:45:17 -0700")
Hi, Dave,
Dave Hansen <dave.hansen@linux.intel.com> writes:
> From: Dave Hansen <dave.hansen@linux.intel.com>
>
> Some method is obviously needed to enable reclaim-based migration.
>
> Just like traditional autonuma, there will be some workloads that
> will benefit like workloads with more "static" configurations where
> hot pages stay hot and cold pages stay cold. If pages come and go
> from the hot and cold sets, the benefits of this approach will be
> more limited.
>
> The benefits are truly workload-based and *not* hardware-based.
> We do not believe that there is a viable threshold where certain
> hardware configurations should have this mechanism enabled while
> others do not.
>
> To be conservative, earlier work defaulted to disable reclaim-
> based migration and did not include a mechanism to enable it.
> This propses extending the existing "zone_reclaim_mode" (now
> now really node_reclaim_mode) as a method to enable it.
>
> We are open to any alternative that allows end users to enable
> this mechanism or disable it it workload harm is detected (just
> like traditional autonuma).
>
> The implementation here is pretty simple and entirely unoptimized.
> On any memory hotplug events, assume that a node was added or
> removed and recalculate all migration targets. This ensures that
> the node_demotion[] array is always ready to be used in case the
> new reclaim mode is enabled. This recalculation is far from
> optimal, most glaringly that it does not even attempt to figure
> out if nodes are actually coming or going.
>
> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
> Cc: Yang Shi <yang.shi@linux.alibaba.com>
> Cc: David Rientjes <rientjes@google.com>
> Cc: Huang Ying <ying.huang@intel.com>
> Cc: Dan Williams <dan.j.williams@intel.com>
> ---
>
> b/Documentation/admin-guide/sysctl/vm.rst | 9 ++++
> b/mm/migrate.c | 61 +++++++++++++++++++++++++++++-
> b/mm/vmscan.c | 7 +--
> 3 files changed, 73 insertions(+), 4 deletions(-)
>
> diff -puN Documentation/admin-guide/sysctl/vm.rst~enable-numa-demotion Documentation/admin-guide/sysctl/vm.rst
> --- a/Documentation/admin-guide/sysctl/vm.rst~enable-numa-demotion 2020-06-29 16:35:01.012312549 -0700
> +++ b/Documentation/admin-guide/sysctl/vm.rst 2020-06-29 16:35:01.021312549 -0700
> @@ -941,6 +941,7 @@ This is value OR'ed together of
> 1 (bit currently ignored)
> 2 Zone reclaim writes dirty pages out
> 4 Zone reclaim swaps pages
> +8 Zone reclaim migrates pages
> = ===================================
>
> zone_reclaim_mode is disabled by default. For file servers or workloads
> @@ -965,3 +966,11 @@ of other processes running on other node
> Allowing regular swap effectively restricts allocations to the local
> node unless explicitly overridden by memory policies or cpuset
> configurations.
> +
> +Page migration during reclaim is intended for systems with tiered memory
> +configurations. These systems have multiple types of memory with varied
> +performance characteristics instead of plain NUMA systems where the same
> +kind of memory is found at varied distances. Allowing page migration
> +during reclaim enables these systems to migrate pages from fast tiers to
> +slow tiers when the fast tier is under pressure. This migration is
> +performed before swap.
> diff -puN mm/migrate.c~enable-numa-demotion mm/migrate.c
> --- a/mm/migrate.c~enable-numa-demotion 2020-06-29 16:35:01.015312549 -0700
> +++ b/mm/migrate.c 2020-06-29 16:35:01.022312549 -0700
> @@ -49,6 +49,7 @@
> #include <linux/sched/mm.h>
> #include <linux/ptrace.h>
> #include <linux/oom.h>
> +#include <linux/memory.h>
>
> #include <asm/tlbflush.h>
>
> @@ -3165,6 +3166,10 @@ void set_migration_target_nodes(void)
> * Avoid any oddities like cycles that could occur
> * from changes in the topology. This will leave
> * a momentary gap when migration is disabled.
> + *
> + * This is superfluous for memory offlining since
> + * MEM_GOING_OFFLINE does it independently, but it
> + * does not hurt to do it a second time.
> */
> disable_all_migrate_targets();
>
> @@ -3211,6 +3216,60 @@ again:
> /* Is another pass necessary? */
> if (!nodes_empty(next_pass))
> goto again;
> +}
>
> - put_online_mems();
> +/*
> + * React to hotplug events that might online or offline
> + * NUMA nodes.
> + *
> + * This leaves migrate-on-reclaim transiently disabled
> + * between the MEM_GOING_OFFLINE and MEM_OFFLINE events.
> + * This runs whether RECLAIM_MIGRATE is enabled or not.
> + * That ensures that the user can turn RECLAIM_MIGRATE
> + * without needing to recalcuate migration targets.
> + */
> +#if defined(CONFIG_MEMORY_HOTPLUG)
> +static int __meminit migrate_on_reclaim_callback(struct notifier_block *self,
> + unsigned long action, void *arg)
> +{
> + switch (action) {
> + case MEM_GOING_OFFLINE:
> + /*
> + * Make sure there are not transient states where
> + * an offline node is a migration target. This
> + * will leave migration disabled until the offline
> + * completes and the MEM_OFFLINE case below runs.
> + */
> + disable_all_migrate_targets();
> + break;
> + case MEM_OFFLINE:
> + case MEM_ONLINE:
> + /*
> + * Recalculate the target nodes once the node
> + * reaches its final state (online or offline).
> + */
> + set_migration_target_nodes();
> + break;
> + case MEM_CANCEL_OFFLINE:
> + /*
> + * MEM_GOING_OFFLINE disabled all the migration
> + * targets. Reenable them.
> + */
> + set_migration_target_nodes();
> + break;
> + case MEM_GOING_ONLINE:
> + case MEM_CANCEL_ONLINE:
> + break;
> + }
> +
> + return notifier_from_errno(0);
> }
> +
> +static int __init migrate_on_reclaim_init(void)
> +{
> + hotplug_memory_notifier(migrate_on_reclaim_callback, 100);
> + return 0;
> +}
> +late_initcall(migrate_on_reclaim_init);
> +#endif /* CONFIG_MEMORY_HOTPLUG */
> +
> diff -puN mm/vmscan.c~enable-numa-demotion mm/vmscan.c
> --- a/mm/vmscan.c~enable-numa-demotion 2020-06-29 16:35:01.017312549 -0700
> +++ b/mm/vmscan.c 2020-06-29 16:35:01.023312549 -0700
> @@ -4165,9 +4165,10 @@ int node_reclaim_mode __read_mostly;
> * These bit locations are exposed in the vm.zone_reclaim_mode sysctl
> * ABI. New bits are OK, but existing bits can never change.
> */
> -#define RECLAIM_RSVD (1<<0) /* (currently ignored/unused) */
> -#define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
> -#define RECLAIM_UNMAP (1<<2) /* Unmap pages during reclaim */
> +#define RECLAIM_RSVD (1<<0) /* (currently ignored/unused) */
> +#define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
> +#define RECLAIM_UNMAP (1<<2) /* Unmap pages during reclaim */
> +#define RECLAIM_MIGRATE (1<<3) /* Migrate pages during reclaim */
>
> /*
> * Priority for NODE_RECLAIM. This determines the fraction of pages
I found that RECLAIM_MIGRATE is defined but never referenced in the
patch.
If my understanding of the code were correct, shrink_do_demote_mapping()
is called by shrink_page_list(), which is used by kswapd and direct
reclaim. So as long as the persistent memory node is onlined,
reclaim-based migration will be enabled regardless of node reclaim mode.
Best Regards,
Huang, Ying
next prev parent reply other threads:[~2020-06-30 7:23 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-29 23:45 [RFC][PATCH 0/8] Migrate Pages in lieu of discard Dave Hansen
2020-06-29 23:45 ` [RFC][PATCH 1/8] mm/numa: node demotion data structure and lookup Dave Hansen
2020-06-29 23:45 ` [RFC][PATCH 2/8] mm/migrate: Defer allocating new page until needed Dave Hansen
2020-07-01 8:47 ` Greg Thelen
2020-07-01 14:46 ` Dave Hansen
2020-07-01 18:32 ` Yang Shi
2020-06-29 23:45 ` [RFC][PATCH 3/8] mm/vmscan: Attempt to migrate page in lieu of discard Dave Hansen
2020-07-01 0:47 ` David Rientjes
2020-07-01 1:29 ` Yang Shi
2020-07-01 5:41 ` David Rientjes
2020-07-01 8:54 ` Huang, Ying
2020-07-01 18:20 ` Dave Hansen
2020-07-01 19:50 ` David Rientjes
2020-07-02 1:50 ` Huang, Ying
2020-07-01 15:15 ` Dave Hansen
2020-07-01 17:21 ` Yang Shi
2020-07-01 19:45 ` David Rientjes
2020-07-02 10:02 ` Jonathan Cameron
2020-07-01 1:40 ` Huang, Ying
2020-07-01 16:48 ` Dave Hansen
2020-07-01 19:25 ` David Rientjes
2020-07-02 5:02 ` Huang, Ying
2020-06-29 23:45 ` [RFC][PATCH 4/8] mm/vmscan: add page demotion counter Dave Hansen
2020-06-29 23:45 ` [RFC][PATCH 5/8] mm/numa: automatically generate node migration order Dave Hansen
2020-06-30 8:22 ` Huang, Ying
2020-07-01 18:23 ` Dave Hansen
2020-07-02 1:20 ` Huang, Ying
2020-06-29 23:45 ` [RFC][PATCH 6/8] mm/vmscan: Consider anonymous pages without swap Dave Hansen
2020-06-29 23:45 ` [RFC][PATCH 7/8] mm/vmscan: never demote for memcg reclaim Dave Hansen
2020-06-29 23:45 ` [RFC][PATCH 8/8] mm/numa: new reclaim mode to enable reclaim-based migration Dave Hansen
2020-06-30 7:23 ` Huang, Ying [this message]
2020-06-30 17:50 ` Yang Shi
2020-07-01 0:48 ` Huang, Ying
2020-07-01 1:12 ` Yang Shi
2020-07-01 1:28 ` Huang, Ying
2020-07-01 16:02 ` Dave Hansen
2020-07-03 9:30 ` Huang, Ying
2020-06-30 18:36 ` [RFC][PATCH 0/8] Migrate Pages in lieu of discard Shakeel Butt
2020-06-30 18:51 ` Dave Hansen
2020-06-30 19:25 ` Shakeel Butt
2020-06-30 19:31 ` Dave Hansen
2020-07-01 14:24 ` [RFC] [PATCH " Zi Yan
2020-07-01 14:32 ` Dave Hansen
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