From: Oscar Salvador <osalvador@suse.de>
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,
ying.huang@intel.com, dan.j.williams@intel.com
Subject: Re: [RFC][PATCH 08/13] mm/migrate: demote pages during reclaim
Date: Tue, 2 Feb 2021 12:55:16 +0100 [thread overview]
Message-ID: <20210202115516.GC12139@linux> (raw)
In-Reply-To: <20210126003427.73DFDD34@viggo.jf.intel.com>
On Mon, Jan 25, 2021 at 04:34:27PM -0800, Dave Hansen wrote:
>
> From: Dave Hansen <dave.hansen@linux.intel.com>
>
> This is mostly derived from a patch from Yang Shi:
>
> https://lore.kernel.org/linux-mm/1560468577-101178-10-git-send-email-yang.shi@linux.alibaba.com/
>
> Add code to the reclaim path (shrink_page_list()) to "demote" data
> to another NUMA node instead of discarding the data. This always
> avoids the cost of I/O needed to read the page back in and sometimes
> avoids the writeout cost when the pagee is dirty.
>
> A second pass through shrink_page_list() will be made if any demotions
> fail. This essentally falls back to normal reclaim behavior in the
> case that demotions fail. Previous versions of this patch may have
> simply failed to reclaim pages which were eligible for demotion but
> were unable to be demoted in practice.
>
> Note: This just adds the start of infratructure for migration. It is
> actually disabled next to the FIXME in migrate_demote_page_ok().
>
> 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>
> Cc: osalvador <osalvador@suse.de>
>
> --
>
> changes from 202010:
> * add MR_NUMA_MISPLACED to trace MIGRATE_REASON define
> * make migrate_demote_page_ok() static, remove 'sc' arg until
> later patch
> * remove unnecessary alloc_demote_page() hugetlb warning
> * Simplify alloc_demote_page() gfp mask. Depend on
> __GFP_NORETRY to make it lightweight instead of fancier
> stuff like leaving out __GFP_IO/FS.
> * Allocate migration page with alloc_migration_target()
> instead of allocating directly.
> changes from 20200730:
> * Add another pass through shrink_page_list() when demotion
> fails.
> ---
[...]
> +static struct page *alloc_demote_page(struct page *page, unsigned long node)
> +{
> + struct migration_target_control mtc = {
> + /*
> + * Fail quickly and quietly. Page will likely
> + * just be discarded instead of migrated.
> + */
> + .gfp_mask = GFP_HIGHUSER | __GFP_NORETRY | __GFP_NOWARN,
> + .nid = node
> + };
> +
> + return alloc_migration_target(page, (unsigned long)&mtc);
> +}
Migration for THP pages will set direct reclaim. I guess that is fine right?
AFAIK, direct reclaim will only be tried once with GFP_NORETRY.
> +
> +/*
> + * Take pages on @demote_list and attempt to demote them to
> + * another node. Pages which are not demoted are left on
> + * @demote_pages.
> + */
> +static unsigned int demote_page_list(struct list_head *demote_pages,
> + struct pglist_data *pgdat,
> + struct scan_control *sc)
> +{
> + int target_nid = next_demotion_node(pgdat->node_id);
> + unsigned int nr_succeeded = 0;
> + int err;
> +
> + if (list_empty(demote_pages))
> + return 0;
> +
> + /* Demotion ignores all cpuset and mempolicy settings */
> + err = migrate_pages(demote_pages, alloc_demote_page, NULL,
> + target_nid, MIGRATE_ASYNC, MR_DEMOTION,
> + &nr_succeeded);
> +
> + return nr_succeeded;
> +}
> +
> /*
> * shrink_page_list() returns the number of reclaimed pages
> */
> @@ -1078,12 +1135,15 @@ static unsigned int shrink_page_list(str
> {
> LIST_HEAD(ret_pages);
> LIST_HEAD(free_pages);
> + LIST_HEAD(demote_pages);
> unsigned int nr_reclaimed = 0;
> unsigned int pgactivate = 0;
> + bool do_demote_pass = true;
>
> memset(stat, 0, sizeof(*stat));
> cond_resched();
>
> +retry:
> while (!list_empty(page_list)) {
> struct address_space *mapping;
> struct page *page;
> @@ -1233,6 +1293,16 @@ static unsigned int shrink_page_list(str
> }
>
> /*
> + * Before reclaiming the page, try to relocate
> + * its contents to another node.
> + */
> + if (do_demote_pass && migrate_demote_page_ok(page)) {
> + list_add(&page->lru, &demote_pages);
> + unlock_page(page);
> + continue;
> + }
Should we keep it simple for now and only try to demote those pages that are
free of cpusets and memory policies?
Actually, demoting those pages to a CPU or a NUMA node that does not fall into
their set, would violate those constraints right?
So I think we should leave those pages alone for now.
> +
> + /*
> * Anonymous process memory has backing store?
> * Try to allocate it some swap space here.
> * Lazyfree page could be freed directly
> @@ -1479,6 +1549,17 @@ keep:
> list_add(&page->lru, &ret_pages);
> VM_BUG_ON_PAGE(PageLRU(page) || PageUnevictable(page), page);
> }
> + /* 'page_list' is always empty here */
> +
> + /* Migrate pages selected for demotion */
> + nr_reclaimed += demote_page_list(&demote_pages, pgdat, sc);
> + /* Pages that could not be demoted are still in @demote_pages */
> + if (!list_empty(&demote_pages)) {
> + /* Pages which failed to demoted go back on on @page_list for retry: */
> + list_splice_init(&demote_pages, page_list);
> + do_demote_pass = false;
> + goto retry;
> + }
>
> pgactivate = stat->nr_activate[0] + stat->nr_activate[1];
>
> _
>
--
Oscar Salvador
SUSE L3
next prev parent reply other threads:[~2021-02-02 11:55 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-26 0:34 [RFC][PATCH 00/13] [v5] Migrate Pages in lieu of discard Dave Hansen
2021-01-26 0:34 ` [RFC][PATCH 01/13] mm/vmscan: restore zone_reclaim_mode ABI Dave Hansen
2021-02-10 9:42 ` Oscar Salvador
2021-01-26 0:34 ` [RFC][PATCH 02/13] mm/vmscan: move RECLAIM* bits to uapi header Dave Hansen
2021-02-10 9:44 ` Oscar Salvador
2021-01-26 0:34 ` [RFC][PATCH 03/13] mm/vmscan: replace implicit RECLAIM_ZONE checks with explicit checks Dave Hansen
2021-01-31 1:10 ` David Rientjes
2021-02-10 9:54 ` Oscar Salvador
2021-01-26 0:34 ` [RFC][PATCH 04/13] mm/numa: node demotion data structure and lookup Dave Hansen
2021-01-31 1:19 ` David Rientjes
2021-02-01 17:49 ` Dave Hansen
2021-01-26 0:34 ` [RFC][PATCH 05/13] mm/numa: automatically generate node migration order Dave Hansen
2021-01-29 20:46 ` Yang Shi
2021-02-01 19:13 ` Dave Hansen
2021-02-02 11:43 ` Oscar Salvador
2021-02-02 17:46 ` Yang Shi
2021-02-03 0:43 ` Dave Hansen
2021-02-04 0:26 ` Yang Shi
2021-01-26 0:34 ` [RFC][PATCH 06/13] mm/migrate: update migration order during on hotplug events Dave Hansen
2021-01-29 20:59 ` Yang Shi
2021-02-02 11:42 ` Oscar Salvador
2021-02-09 23:45 ` Dave Hansen
2021-02-10 8:55 ` Oscar Salvador
2021-01-26 0:34 ` [RFC][PATCH 07/13] mm/migrate: make migrate_pages() return nr_succeeded Dave Hansen
2021-01-29 21:04 ` Yang Shi
2021-02-09 23:41 ` Dave Hansen
2021-01-26 0:34 ` [RFC][PATCH 08/13] mm/migrate: demote pages during reclaim Dave Hansen
2021-02-02 11:55 ` Oscar Salvador [this message]
2021-02-02 22:45 ` Yang Shi
2021-02-02 22:56 ` Dave Hansen
2021-02-02 18:22 ` Yang Shi
2021-02-02 18:34 ` Dave Hansen
2021-01-26 0:34 ` [RFC][PATCH 09/13] mm/vmscan: add page demotion counter Dave Hansen
2021-01-26 0:34 ` [RFC][PATCH 10/13] mm/vmscan: add helper for querying ability to age anonymous pages Dave Hansen
2021-01-26 0:34 ` [RFC][PATCH 11/13] mm/vmscan: Consider anonymous pages without swap Dave Hansen
2021-02-02 18:56 ` Yang Shi
2021-02-02 21:35 ` Dave Hansen
2021-02-02 22:35 ` Yang Shi
2021-01-26 0:34 ` [RFC][PATCH 12/13] mm/vmscan: never demote for memcg reclaim Dave Hansen
2021-01-26 0:34 ` [RFC][PATCH 13/13] mm/migrate: new zone_reclaim_mode to enable reclaim migration Dave Hansen
2021-01-31 1:13 ` [RFC][PATCH 00/13] [v5] Migrate Pages in lieu of discard David Rientjes
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