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From: Oscar Salvador <osalvador@suse.de>
To: David Hildenbrand <david@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Mike Kravetz <mike.kravetz@oracle.com>,
	Muchun Song <songmuchun@bytedance.com>,
	Michal Hocko <mhocko@kernel.org>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 0/2] Make alloc_contig_range handle Hugetlb pages
Date: Mon, 1 Mar 2021 13:57:59 +0100	[thread overview]
Message-ID: <20210301125754.GA4003@linux> (raw)
In-Reply-To: <ff780dd6-f473-5476-fc1c-9f9bbcdb17c8@redhat.com>

On Mon, Mar 01, 2021 at 01:43:00PM +0100, David Hildenbrand wrote:
> Same experiment with ZONE_MOVABLE:
> 
> a) Free huge pages: all memory can get unplugged again.
> 
> b) Allocated/populated but idle huge pages: all memory can get unplugged
> again.
> 
> c) Allocated/populated but all 512 huge pages are read/written in a loop:
> all memory can get unplugged again, but I get a single
> 
> [  121.192345] alloc_contig_range: [180000, 188000) PFNs busy
> 
> Most probably because it happened to try migrating a huge page while it was
> busy. As virtio-mem retries on ZONE_MOVABLE a couple of times, it can deal
> with this temporary failure.
> 
> 
> 
> Last but not least, I did something extreme:
> 
> ]# cat /proc/meminfo
> MemTotal:        5061568 kB
> MemFree:          186560 kB
> MemAvailable:     354524 kB
> ...
> HugePages_Total:    2048
> HugePages_Free:     2048
> HugePages_Rsvd:        0
> HugePages_Surp:        0
> 
> 
> Triggering unplug would require to dissolve+alloc - which now fails when
> trying to allocate an additional ~512 huge pages (1G).
> 
> 
> As expected, I can properly see memory unplug not fully succeeding. + I get
> a fairly continuous stream of
> 
> [  226.611584] alloc_contig_range: [19f400, 19f800) PFNs busy
> ...
> 
> But more importantly, the hugepage count remains stable, as configured by
> the admin (me):
> 
> HugePages_Total:    2048
> HugePages_Free:     2048
> HugePages_Rsvd:        0
> HugePages_Surp:        0

Thanks for giving it a spin David, that is highly appreciated ;-)!

I will add above information in next's version changelog if you do not mind,
so the before-and-after can be seen clearly.

I shall send v4 in the course of the next few days.

-- 
Oscar Salvador
SUSE L3


  reply	other threads:[~2021-03-01 12:58 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-22 13:51 [PATCH v3 0/2] Make alloc_contig_range handle Hugetlb pages Oscar Salvador
2021-02-22 13:51 ` [PATCH v3 1/2] mm: Make alloc_contig_range handle free hugetlb pages Oscar Salvador
2021-02-25 20:03   ` Mike Kravetz
2021-02-26  9:48     ` Oscar Salvador
2021-02-26  8:35   ` Michal Hocko
2021-02-26  8:38     ` Michal Hocko
2021-02-26  9:25       ` David Hildenbrand
2021-02-26  9:47         ` Oscar Salvador
2021-02-26  9:45     ` Oscar Salvador
2021-02-26  9:51       ` Michal Hocko
2021-03-01 14:09   ` David Hildenbrand
2021-03-04 10:19     ` Oscar Salvador
2021-03-04 10:32       ` David Hildenbrand
2021-03-04 10:41         ` Oscar Salvador
2021-02-22 13:51 ` [PATCH v3 2/2] mm: Make alloc_contig_range handle in-use " Oscar Salvador
2021-02-25 23:05   ` Mike Kravetz
2021-02-26  8:46   ` Michal Hocko
2021-02-26 10:24     ` Oscar Salvador
2021-02-26 10:27       ` Oscar Salvador
2021-02-26 12:46       ` Michal Hocko
2021-02-28 13:43         ` Oscar Salvador
2021-03-05 17:30   ` David Hildenbrand
2021-03-01 12:43 ` [PATCH v3 0/2] Make alloc_contig_range handle Hugetlb pages David Hildenbrand
2021-03-01 12:57   ` Oscar Salvador [this message]
2021-03-01 12:59     ` David Hildenbrand

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