LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: David Hildenbrand <david@redhat.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: linux-mm@kvack.org, Steven Rostedt <rostedt@goodmis.org>,
	Ingo Molnar <mingo@redhat.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Huang Ying <ying.huang@intel.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Pavel Tatashin <pasha.tatashin@oracle.com>,
	Miles Chen <miles.chen@mediatek.com>,
	Vlastimil Babka <vbabka@suse.cz>,
	Mel Gorman <mgorman@techsingularity.net>,
	Rik van Riel <riel@redhat.com>, James Hogan <jhogan@kernel.org>,
	"Levin, Alexander (Sasha Levin)" <alexander.levin@verizon.com>,
	open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH RFC 2/8] mm: introduce PG_offline
Date: Tue, 17 Apr 2018 13:50:01 +0200	[thread overview]
Message-ID: <86717b44-7aad-19d9-b55f-7f9eb40bcaa1@redhat.com> (raw)
In-Reply-To: <20180413134047.GR17484@dhcp22.suse.cz>

On 13.04.2018 15:40, Michal Hocko wrote:
> On Fri 13-04-18 15:16:26, David Hildenbrand wrote:
>> online_pages()/offline_pages() theoretically allows us to work on
>> sub-section sizes. This is especially relevant in the context of
>> virtualization. It e.g. allows us to add/remove memory to Linux in a VM in
>> 4MB chunks.
> 
> Well, theoretically possible but this would require a lot of auditing
> because the hotplug and per section assumption is quite a spread one.
> 
>> While the whole section is marked as online/offline, we have to know
>> the state of each page. E.g. to not read memory that is not online
>> during kexec() or to properly mark a section as offline as soon as all
>> contained pages are offline.
> 
> But you cannot use a page flag for that, I am afraid. Page flags are
> extremely scarce resource. I haven't looked at the rest of the series
> but _if_ we have a bit spare which I am not really sure about then you
> should prove there are no other ways around this.

BTW, looking at the possible layouts of page->flags, I don't think it
will be a problem adding this flag. Especially if we compile this flag
only if really needed.

We could glue this flag to CONFIG_MEMORY_HOTPLUG_SUBSECTION to something
like that, that will be set when our new driver is compiled. So this
would not affect anybody just wanting to use ordinary DIMM based hotplug
(CONFIG_MEMORY_HOTPLUG).

But I am open for other suggestions. I don't think PG_reserved is the
right thing to use. And storing for each section which parts are
online/offline is also something I would like to avoid.

-- 

Thanks,

David / dhildenb

  parent reply	other threads:[~2018-04-17 11:50 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20180413131632.1413-1-david@redhat.com>
2018-04-13 13:16 ` [PATCH RFC 1/8] mm/memory_hotplug: Revert "mm/memory_hotplug: optimize memory hotplug" David Hildenbrand
2018-04-13 13:16 ` [PATCH RFC 2/8] mm: introduce PG_offline David Hildenbrand
2018-04-13 13:40   ` Michal Hocko
2018-04-13 13:46     ` David Hildenbrand
2018-04-17 11:50     ` David Hildenbrand [this message]
2018-04-13 17:11   ` Matthew Wilcox
2018-04-16  8:31     ` David Hildenbrand
2018-04-21 16:52     ` Vlastimil Babka
2018-04-22  3:01       ` Matthew Wilcox
2018-04-22  8:17         ` David Hildenbrand
2018-04-22 14:02           ` Matthew Wilcox
2018-04-22 15:13             ` David Hildenbrand
2018-04-29 21:08               ` Michal Hocko
2018-04-30  6:31                 ` David Hildenbrand
2018-04-20  7:30   ` David Hildenbrand
2018-04-13 13:16 ` [PATCH RFC 3/8] mm: use PG_offline in online/offlining code David Hildenbrand
2018-04-13 13:31 ` [PATCH RFC 4/8] kdump: expose PG_offline David Hildenbrand
2018-04-13 13:33 ` [PATCH RFC 5/8] mm: only mark section offline when all pages are offline David Hildenbrand
2018-04-13 13:33 ` [PATCH RFC 6/8] mm: offline_pages() is also limited by MAX_ORDER David Hildenbrand
2018-04-13 13:33 ` [PATCH RFC 7/8] mm: allow to control onlining/offlining of memory by a driver David Hildenbrand
2018-04-13 15:59   ` Michal Hocko
2018-04-13 16:32     ` David Hildenbrand
2018-04-13 13:33 ` [PATCH RFC 8/8] mm: export more functions used to online/offline memory David Hildenbrand

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=86717b44-7aad-19d9-b55f-7f9eb40bcaa1@redhat.com \
    --to=david@redhat.com \
    --cc=akpm@linux-foundation.org \
    --cc=alexander.levin@verizon.com \
    --cc=gregkh@linuxfoundation.org \
    --cc=jhogan@kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=mgorman@techsingularity.net \
    --cc=mhocko@kernel.org \
    --cc=miles.chen@mediatek.com \
    --cc=mingo@redhat.com \
    --cc=pasha.tatashin@oracle.com \
    --cc=riel@redhat.com \
    --cc=rostedt@goodmis.org \
    --cc=vbabka@suse.cz \
    --cc=ying.huang@intel.com \
    --subject='Re: [PATCH RFC 2/8] mm: introduce PG_offline' \
    /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

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).