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From: David Hildenbrand <david@redhat.com>
To: osalvador@suse.de, Vlastimil Babka <vbabka@suse.cz>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	Michal Hocko <mhocko@kernel.org>,
	Pavel Tatashin <pasha.tatashin@soleen.com>,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>
Subject: Re: [RFC 0/5] disable pcplists during page isolation
Date: Wed, 9 Sep 2020 13:29:40 +0200	[thread overview]
Message-ID: <ee56072e-53be-3f3f-cd6d-d56317f15f0a@redhat.com> (raw)
In-Reply-To: <3f4bd7b0c73f59b4cd2adaad3ccc38bf@suse.de>

On 09.09.20 13:27, osalvador@suse.de wrote:
> On 2020-09-09 12:54, Vlastimil Babka wrote:
>> Thanks! I expect no performance change while no isolation is in 
>> progress, as
>> there are no new tests added in alloc/free paths. During page isolation 
>> there's
>> a single drain instead of once-per-pageblock, which is a benefit. But 
>> the
>> pcplists are effectively disabled for the whole of online_pages(),
>> offline_pages() or alloc_contig_range(), which will affect parallel 
>> page
>> allocator users. It depends on how long these operations take and how 
>> heavy the
>> parallel usage is, so I have no good answers. Might be similar to the 
>> current
>> periodic drain.
> 
> I have seen some systems taking quite some time when offlining sections 
> due to the migration of
> the respective pages not being that smooth and having do_migrate_range 
> to do some spins.
> But to be fair, online_pages and offline_pages are not routines that get 
> called that often, and we would be safe to assume that memory-hotplug 
> operations are not constantly happening, but are rather one-offs 
> operations.
> 
> I am not sure about Xen and HV, IIRC Xen was using online_pages and 
> offline_pages routines to do the ballooning?

No, they only add more memory blocks and online them. Memory hot(un)plug
is an expensive operation already, I don't think that's an issue.

-- 
Thanks,

David / dhildenb


      reply	other threads:[~2020-09-09 11:33 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-07 16:36 [RFC 0/5] disable pcplists during page isolation Vlastimil Babka
2020-09-07 16:36 ` [RFC 1/5] mm, page_alloc: clean up pageset high and batch update Vlastimil Babka
2020-09-10  8:31   ` Oscar Salvador
2020-09-10  8:34     ` Oscar Salvador
2020-09-10 10:47     ` David Hildenbrand
2020-09-17 16:05     ` Vlastimil Babka
2020-09-07 16:36 ` [RFC 2/5] mm, page_alloc: calculate pageset high and batch once per zone Vlastimil Babka
2020-09-10  9:00   ` Oscar Salvador
2020-09-10 10:56   ` David Hildenbrand
2020-09-07 16:36 ` [RFC 3/5] mm, page_alloc(): remove setup_pageset() Vlastimil Babka
2020-09-10  9:23   ` Oscar Salvador
2020-09-10  9:57     ` Oscar Salvador
2020-09-18  9:37     ` Vlastimil Babka
2020-09-10 11:00   ` David Hildenbrand
2020-09-07 16:36 ` [RFC 4/5] mm, page_alloc: cache pageset high and batch in struct zone Vlastimil Babka
2020-09-10 11:30   ` Oscar Salvador
2020-09-18 12:02     ` Vlastimil Babka
2020-09-07 16:36 ` [RFC 5/5] mm, page_alloc: disable pcplists during page isolation Vlastimil Babka
2020-09-09 10:48   ` Vlastimil Babka
2020-09-09 11:36     ` Michal Hocko
2020-09-09 11:44       ` David Hildenbrand
2020-09-09 12:57         ` David Hildenbrand
2020-09-09 11:55       ` Vlastimil Babka
2020-09-10 10:29         ` David Hildenbrand
2020-09-10 11:05           ` Vlastimil Babka
2020-09-10 12:42             ` David Hildenbrand
2020-09-09 12:53       ` Pavel Tatashin
2020-09-09 12:53         ` Pavel Tatashin
2020-09-08 18:29 ` [RFC 0/5] " David Hildenbrand
2020-09-09 10:54   ` Vlastimil Babka
2020-09-09 11:27     ` osalvador
2020-09-09 11:29       ` David Hildenbrand [this message]

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