From: Wei Yang <richard.weiyang@linux.alibaba.com>
To: David Hildenbrand <david@redhat.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
linux-hyperv@vger.kernel.org, xen-devel@lists.xenproject.org,
linux-acpi@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Alexander Duyck <alexander.h.duyck@linux.intel.com>,
Mel Gorman <mgorman@techsingularity.net>,
Michal Hocko <mhocko@kernel.org>,
Dave Hansen <dave.hansen@intel.com>,
Vlastimil Babka <vbabka@suse.cz>,
Wei Yang <richard.weiyang@linux.alibaba.com>,
Oscar Salvador <osalvador@suse.de>,
Mike Rapoport <rppt@kernel.org>,
Scott Cheloha <cheloha@linux.ibm.com>,
Michael Ellerman <mpe@ellerman.id.au>
Subject: Re: [PATCH RFC 2/4] mm/page_alloc: place pages to tail in __putback_isolated_page()
Date: Fri, 18 Sep 2020 10:07:58 +0800 [thread overview]
Message-ID: <20200918020758.GB54754@L-31X9LVDL-1304.local> (raw)
In-Reply-To: <20200916183411.64756-3-david@redhat.com>
On Wed, Sep 16, 2020 at 08:34:09PM +0200, David Hildenbrand wrote:
>__putback_isolated_page() already documents that pages will be placed to
>the tail of the freelist - this is, however, not the case for
>"order >= MAX_ORDER - 2" (see buddy_merge_likely()) - which should be
>the case for all existing users.
>
>This change affects two users:
>- free page reporting
>- page isolation, when undoing the isolation.
>
>This behavior is desireable for pages that haven't really been touched
>lately, so exactly the two users that don't actually read/write page
>content, but rather move untouched pages.
>
>The new behavior is especially desirable for memory onlining, where we
>allow allocation of newly onlined pages via undo_isolate_page_range()
>in online_pages(). Right now, we always place them to the head of the
The code looks good, while I don't fully understand the log here.
undo_isolate_page_range() is used in __offline_pages and alloc_contig_range. I
don't connect them with online_pages(). Do I miss something?
>free list, resulting in undesireable behavior: Assume we add
>individual memory chunks via add_memory() and online them right away to
>the NORMAL zone. We create a dependency chain of unmovable allocations
>e.g., via the memmap. The memmap of the next chunk will be placed onto
>previous chunks - if the last block cannot get offlined+removed, all
>dependent ones cannot get offlined+removed. While this can already be
>observed with individual DIMMs, it's more of an issue for virtio-mem
>(and I suspect also ppc DLPAR).
>
>Note: If we observe a degradation due to the changed page isolation
>behavior (which I doubt), we can always make this configurable by the
>instance triggering undo of isolation (e.g., alloc_contig_range(),
>memory onlining, memory offlining).
>
>Cc: Andrew Morton <akpm@linux-foundation.org>
>Cc: Alexander Duyck <alexander.h.duyck@linux.intel.com>
>Cc: Mel Gorman <mgorman@techsingularity.net>
>Cc: Michal Hocko <mhocko@kernel.org>
>Cc: Dave Hansen <dave.hansen@intel.com>
>Cc: Vlastimil Babka <vbabka@suse.cz>
>Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
>Cc: Oscar Salvador <osalvador@suse.de>
>Cc: Mike Rapoport <rppt@kernel.org>
>Cc: Scott Cheloha <cheloha@linux.ibm.com>
>Cc: Michael Ellerman <mpe@ellerman.id.au>
>Signed-off-by: David Hildenbrand <david@redhat.com>
>---
> mm/page_alloc.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
>diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>index 91cefb8157dd..bba9a0f60c70 100644
>--- a/mm/page_alloc.c
>+++ b/mm/page_alloc.c
>@@ -89,6 +89,12 @@ typedef int __bitwise fop_t;
> */
> #define FOP_SKIP_REPORT_NOTIFY ((__force fop_t)BIT(0))
>
>+/*
>+ * Place the freed page to the tail of the freelist after buddy merging. Will
>+ * get ignored with page shuffling enabled.
>+ */
>+#define FOP_TO_TAIL ((__force fop_t)BIT(1))
>+
> /* prevent >1 _updater_ of zone percpu pageset ->high and ->batch fields */
> static DEFINE_MUTEX(pcp_batch_high_lock);
> #define MIN_PERCPU_PAGELIST_FRACTION (8)
>@@ -1040,6 +1046,8 @@ static inline void __free_one_page(struct page *page, unsigned long pfn,
>
> if (is_shuffle_order(order))
> to_tail = shuffle_pick_tail();
>+ else if (fop_flags & FOP_TO_TAIL)
>+ to_tail = true;
> else
> to_tail = buddy_merge_likely(pfn, buddy_pfn, page, order);
>
>@@ -3289,7 +3297,7 @@ void __putback_isolated_page(struct page *page, unsigned int order, int mt)
>
> /* Return isolated page to tail of freelist. */
> __free_one_page(page, page_to_pfn(page), zone, order, mt,
>- FOP_SKIP_REPORT_NOTIFY);
>+ FOP_SKIP_REPORT_NOTIFY | FOP_TO_TAIL);
> }
>
> /*
>--
>2.26.2
--
Wei Yang
Help you, Help me
next prev parent reply other threads:[~2020-09-18 2:52 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-16 18:34 [PATCH RFC 0/4] mm: place pages to the freelist tail when onling and undoing isolation David Hildenbrand
2020-09-16 18:34 ` [PATCH RFC 1/4] mm/page_alloc: convert "report" flag of __free_one_page() to a proper flag David Hildenbrand
2020-09-16 21:44 ` Alexander Duyck
2020-09-18 1:53 ` Wei Yang
2020-09-18 7:23 ` David Hildenbrand
2020-09-24 10:19 ` Vlastimil Babka
2020-09-25 10:34 ` Oscar Salvador
2020-09-16 18:34 ` [PATCH RFC 2/4] mm/page_alloc: place pages to tail in __putback_isolated_page() David Hildenbrand
2020-09-16 21:50 ` Alexander Duyck
2020-09-18 2:07 ` Wei Yang [this message]
2020-09-18 7:27 ` David Hildenbrand
2020-09-21 1:57 ` Wei Yang
2020-09-18 2:16 ` Wei Yang
2020-09-18 7:29 ` David Hildenbrand
2020-09-24 10:37 ` Vlastimil Babka
2020-09-25 8:10 ` David Hildenbrand
2020-09-25 13:19 ` Oscar Salvador
2020-09-25 13:30 ` David Hildenbrand
2020-09-16 18:34 ` [PATCH RFC 3/4] mm/page_alloc: always move pages to the tail of the freelist in unset_migratetype_isolate() David Hildenbrand
2020-09-18 2:29 ` Wei Yang
2020-09-18 7:30 ` David Hildenbrand
2020-09-24 11:13 ` Vlastimil Babka
2020-09-25 2:45 ` Wei Yang
2020-09-25 8:05 ` David Hildenbrand
2020-09-25 8:39 ` Vlastimil Babka
2020-09-25 13:13 ` David Hildenbrand
2020-09-25 13:57 ` Oscar Salvador
2020-09-16 18:34 ` [PATCH RFC 4/4] mm/page_alloc: place pages to tail in __free_pages_core() David Hildenbrand
2020-09-24 13:44 ` Vlastimil Babka
2020-09-28 7:58 ` Oscar Salvador
2020-09-28 8:36 ` David Hildenbrand
2020-09-28 12:53 ` Oscar Salvador
2020-09-16 18:50 ` [PATCH RFC 0/4] mm: place pages to the freelist tail when onling and undoing isolation osalvador
2020-09-16 19:31 ` David Hildenbrand
2020-09-18 2:30 ` Wei Yang
2020-09-18 7:32 ` David Hildenbrand
2020-09-23 14:31 ` Vlastimil Babka
2020-09-23 15:26 ` David Hildenbrand
2020-09-24 9:40 ` Mel Gorman
2020-09-24 9:54 ` David Hildenbrand
2020-09-24 13:59 ` Vlastimil Babka
2020-09-24 14:29 ` David Hildenbrand
2020-09-24 1:57 ` Wei Yang
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=20200918020758.GB54754@L-31X9LVDL-1304.local \
--to=richard.weiyang@linux.alibaba.com \
--cc=akpm@linux-foundation.org \
--cc=alexander.h.duyck@linux.intel.com \
--cc=cheloha@linux.ibm.com \
--cc=dave.hansen@intel.com \
--cc=david@redhat.com \
--cc=linux-acpi@vger.kernel.org \
--cc=linux-hyperv@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mgorman@techsingularity.net \
--cc=mhocko@kernel.org \
--cc=mpe@ellerman.id.au \
--cc=osalvador@suse.de \
--cc=rppt@kernel.org \
--cc=vbabka@suse.cz \
--cc=xen-devel@lists.xenproject.org \
/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
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).