Linux-mm Archive on lore.kernel.org
 help / color / Atom feed
From: Anshuman Khandual <anshuman.khandual@arm.com>
To: Qian Cai <cai@lca.pw>
Cc: linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
	Michal Hocko <mhocko@suse.com>, Vlastimil Babka <vbabka@suse.cz>,
	Oscar Salvador <osalvador@suse.de>,
	Mel Gorman <mgorman@techsingularity.net>,
	Mike Rapoport <rppt@linux.ibm.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Pavel Tatashin <pavel.tatashin@microsoft.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm/page_alloc: Add a reason for reserved pages in has_unmovable_pages()
Date: Thu, 3 Oct 2019 17:32:02 +0530
Message-ID: <49fa7dea-00ac-155f-e7b7-eeca206556b5@arm.com> (raw)
In-Reply-To: <983E7EA4-A022-448C-B11D-8C10441A2E07@lca.pw>



On 10/03/2019 05:20 PM, Qian Cai wrote:
> 
> 
>> On Oct 3, 2019, at 7:31 AM, Anshuman Khandual <Anshuman.Khandual@arm.com> wrote:
>>
>> Ohh, never meant that the 'Reserved' bit is anything special here but it
>> is a reason to make a page unmovable unlike many other flags.
> 
> But dump_page() is used everywhere, and it is better to reserve “reason” to indicate something more important rather than duplicating the page flags.
> 
> Especially, it is trivial enough right now for developers look in the page flags dumping from has_unmovable_pages(), and figure out the exact branching in the code.
> 

Will something like this be better ? hugepage_migration_supported() has got
uncertainty depending on platform and huge page size.

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 15c2050c629b..8dbc86696515 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -8175,7 +8175,7 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count,
        unsigned long found;
        unsigned long iter = 0;
        unsigned long pfn = page_to_pfn(page);
-       const char *reason = "unmovable page";
+       const char *reason;

        /*
         * TODO we could make this much more efficient by not checking every
@@ -8194,7 +8194,7 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count,
                if (is_migrate_cma(migratetype))
                        return false;

-               reason = "CMA page";
+               reason = "Unmovable CMA page";
                goto unmovable;
        }

@@ -8206,8 +8206,10 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count,

                page = pfn_to_page(check);

-               if (PageReserved(page))
+               if (PageReserved(page)) {
+                       reason = "Unmovable reserved page";
                        goto unmovable;
+               }

                /*
                 * If the zone is movable and we have ruled out all reserved
@@ -8226,8 +8228,10 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count,
                        struct page *head = compound_head(page);
                        unsigned int skip_pages;

-                       if (!hugepage_migration_supported(page_hstate(head)))
+                       if (!hugepage_migration_supported(page_hstate(head))) {
+                               reason = "Unmovable HugeTLB page";
                                goto unmovable;
+                       }

                        skip_pages = compound_nr(head) - (page - head);
                        iter += skip_pages - 1;
@@ -8271,8 +8275,10 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count,
                 * is set to both of a memory hole page and a _used_ kernel
                 * page at boot.
                 */
-               if (found > count)
+               if (found > count) {
+                       reason = "Unmovable non-LRU page";
                        goto unmovable;
+               }
        }
        return false;
 unmovable:


  reply index

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-03  8:10 Anshuman Khandual
2019-10-03  9:05 ` Qian Cai
2019-10-03  9:32   ` Anshuman Khandual
2019-10-03  9:53     ` Anshuman Khandual
2019-10-03 11:19     ` Qian Cai
2019-10-03 11:32       ` Anshuman Khandual
2019-10-03 11:50         ` Qian Cai
2019-10-03 12:02           ` Anshuman Khandual [this message]
2019-10-03 12:14             ` Qian Cai
2019-10-04  8:25               ` David Hildenbrand
2020-01-14  8:19                 ` Anshuman Khandual
2020-01-14  8:30                   ` David Hildenbrand
2020-01-14  9:10                   ` Michal Hocko
2020-01-14 10:23                     ` Vlastimil Babka
2020-01-14 11:03                       ` Anshuman Khandual
2020-01-14 11:32                       ` Michal Hocko
2020-01-14 12:04                         ` [PATCH] mm, debug: always print flags in dump_page() Vlastimil Babka
2020-01-14 13:35                           ` Michal Hocko
2020-01-14 18:22                         ` [PATCH] mm/page_alloc: Add a reason for reserved pages in has_unmovable_pages() Ralph Campbell
2019-10-04 10:58 ` Michal Hocko
2019-10-04 11:44   ` Anshuman Khandual
2019-10-04 12:56     ` Qian Cai
2019-10-04 13:07       ` Michal Hocko
2019-10-04 13:30         ` Qian Cai
2019-10-04 13:38           ` Michal Hocko
2019-10-04 13:56             ` Qian Cai
2019-10-04 14:41               ` Michal Hocko
2019-10-05 21:22                 ` Andrew Morton
2019-10-05 22:38                   ` Qian Cai

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=49fa7dea-00ac-155f-e7b7-eeca206556b5@arm.com \
    --to=anshuman.khandual@arm.com \
    --cc=akpm@linux-foundation.org \
    --cc=cai@lca.pw \
    --cc=dan.j.williams@intel.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=mgorman@techsingularity.net \
    --cc=mhocko@suse.com \
    --cc=osalvador@suse.de \
    --cc=pavel.tatashin@microsoft.com \
    --cc=rppt@linux.ibm.com \
    --cc=vbabka@suse.cz \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-mm Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-mm/0 linux-mm/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-mm linux-mm/ https://lore.kernel.org/linux-mm \
		linux-mm@kvack.org
	public-inbox-index linux-mm

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kvack.linux-mm


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git