From: Michal Hocko <mhocko@suse.com>
To: Oscar Salvador <osalvador@suse.de>
Cc: David Hildenbrand <david@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Anshuman Khandual <anshuman.khandual@arm.com>,
Vlastimil Babka <vbabka@suse.cz>,
Pavel Tatashin <pasha.tatashin@soleen.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5 1/5] mm,memory_hotplug: Allocate memmap from the added memory range
Date: Thu, 25 Mar 2021 15:40:04 +0100 [thread overview]
Message-ID: <YFygxF5Rx0ESCfKB@dhcp22.suse.cz> (raw)
In-Reply-To: <YFyX8jRWqfqCoGo/@localhost.localdomain>
On Thu 25-03-21 15:02:26, Oscar Salvador wrote:
> On Thu, Mar 25, 2021 at 01:26:34PM +0100, Michal Hocko wrote:
> > Yeah, David has raised the contiguous flag for zone already. And to be
> > completely honest I fail to see why we should shape a design based on an
> > optimization. If anything we can teach set_zone_contiguous to simply
> > ignore zone affiliation of vmemmap pages. I would be really curious if
> > that would pose any harm to the compaction code as they are reserved and
> > compaction should simply skip them.
>
> No, compaction code is clever enough to skip over those pages as it
> already does for any Reserved page.
> My comment was more towards having the zone contiguous.
>
> I know it is an optimization, but
>
> commit 7cf91a98e607c2f935dbcc177d70011e95b8faff
> Author: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> Date: Tue Mar 15 14:57:51 2016 -0700
>
> mm/compaction: speed up pageblock_pfn_to_page() when zone is contiguous
>
> talks about 30% of improvment. I am not sure if those numbers would
> still hold nowawadys, but it feels wrong to drop it to the ground when
> we can do better there, and IMHO, it does not overly complicate things.
Again, do not shape design around an optimization. If this turns out a
real problem then it can be handled on top.
> > THere is nothing like a proper zone.
>
> I guess not, but for me it makes sense that vmemmap pages stay within
> the same zone as the pages they describe.
This is not the case for normal hotplug so why this should be any
different.
> Of course, this is a matter of opinions/taste.
>
> > Not sure what you are referring to but if you have prior to f1dd2cd13c4b
> > ("mm, memory_hotplug: do not associate hotadded memory to zones until
> > online") then this was entirely a different story. Users do care where
> > they memory goes because that depends on the usecase but do they care
> > about vmemmap?
>
> As I said, that is not what I am worried about.
> Users do not really care where those pages end up, that is transparent
> to them (wrt. vmemmap pages), but we (internally) kind of do.
>
> So, as I said, I see advantatges of using your way, but I see downsides
> as:
>
> - I would like to consider zone, and for that we would have to pull
> some of the functions that check for the zone at an aearly stage, and
> the mere thought sounds ugly.
This is impossible and whatever kind of heuristic you come up with might
be wrong.
> - Section containing vmemmap can remain offline and would have to come
> up to sort that out
Yes, this is a problem indeed and as I've said in other email this would
be a problem for your initial implementation as well if the memory block
is still offline. I suspect we need to treat these Vmemmap pages as
online (via pfn_to_online_page).
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2021-03-25 14:40 UTC|newest]
Thread overview: 63+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-19 9:26 [PATCH v5 0/5] Allocate memmap from hotadded memory (per device) Oscar Salvador
2021-03-19 9:26 ` [PATCH v5 1/5] mm,memory_hotplug: Allocate memmap from the added memory range Oscar Salvador
2021-03-19 10:20 ` David Hildenbrand
2021-03-19 10:31 ` Oscar Salvador
2021-03-19 12:04 ` David Hildenbrand
2021-03-23 10:11 ` Michal Hocko
2021-03-24 10:12 ` Oscar Salvador
2021-03-24 12:03 ` Michal Hocko
2021-03-24 12:10 ` Michal Hocko
2021-03-24 12:23 ` David Hildenbrand
2021-03-24 12:37 ` Michal Hocko
2021-03-24 13:13 ` David Hildenbrand
2021-03-24 13:40 ` Michal Hocko
2021-03-24 14:05 ` David Hildenbrand
2021-03-24 13:27 ` Oscar Salvador
2021-03-24 14:42 ` Michal Hocko
2021-03-24 14:52 ` David Hildenbrand
2021-03-24 16:04 ` Michal Hocko
2021-03-24 19:16 ` David Hildenbrand
2021-03-25 8:07 ` Oscar Salvador
2021-03-25 9:17 ` Michal Hocko
2021-03-25 10:55 ` Oscar Salvador
2021-03-25 11:08 ` David Hildenbrand
2021-03-25 11:23 ` Oscar Salvador
2021-03-25 12:35 ` Michal Hocko
2021-03-25 12:40 ` David Hildenbrand
2021-03-25 14:08 ` Michal Hocko
2021-03-25 14:09 ` David Hildenbrand
2021-03-25 14:34 ` Michal Hocko
2021-03-25 14:46 ` David Hildenbrand
2021-03-25 15:12 ` Michal Hocko
2021-03-25 15:19 ` David Hildenbrand
2021-03-25 15:35 ` Michal Hocko
2021-03-25 15:40 ` David Hildenbrand
2021-03-25 16:07 ` Michal Hocko
2021-03-25 16:20 ` David Hildenbrand
2021-03-25 16:36 ` Michal Hocko
2021-03-25 16:47 ` Michal Hocko
2021-03-25 16:55 ` David Hildenbrand
2021-03-25 22:06 ` Oscar Salvador
2021-03-26 8:35 ` Michal Hocko
2021-03-26 8:52 ` David Hildenbrand
2021-03-26 8:57 ` Oscar Salvador
2021-03-26 12:15 ` Oscar Salvador
2021-03-26 13:36 ` David Hildenbrand
2021-03-26 14:38 ` Michal Hocko
2021-03-26 14:53 ` David Hildenbrand
2021-03-26 15:31 ` Michal Hocko
2021-03-26 16:03 ` David Hildenbrand
2021-03-26 8:55 ` Oscar Salvador
2021-03-26 9:11 ` Michal Hocko
2021-03-25 18:08 ` David Hildenbrand
2021-03-25 12:26 ` Michal Hocko
2021-03-25 14:02 ` Oscar Salvador
2021-03-25 14:40 ` Michal Hocko [this message]
2021-03-19 9:26 ` [PATCH v5 2/5] acpi,memhotplug: Enable MHP_MEMMAP_ON_MEMORY when supported Oscar Salvador
2021-03-23 10:40 ` Michal Hocko
2021-03-19 9:26 ` [PATCH v5 3/5] mm,memory_hotplug: Add kernel boot option to enable memmap_on_memory Oscar Salvador
2021-03-23 10:47 ` Michal Hocko
2021-03-24 8:45 ` Oscar Salvador
2021-03-24 9:02 ` Michal Hocko
2021-03-19 9:26 ` [PATCH v5 4/5] x86/Kconfig: Introduce ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE Oscar Salvador
2021-03-19 9:26 ` [PATCH v5 5/5] arm64/Kconfig: " Oscar Salvador
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=YFygxF5Rx0ESCfKB@dhcp22.suse.cz \
--to=mhocko@suse.com \
--cc=akpm@linux-foundation.org \
--cc=anshuman.khandual@arm.com \
--cc=david@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=osalvador@suse.de \
--cc=pasha.tatashin@soleen.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
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).