From: Jerome Glisse <jglisse@redhat.com>
To: Oscar Salvador <osalvador@techadventures.net>
Cc: Michal Hocko <mhocko@kernel.org>,
akpm@linux-foundation.org, dan.j.williams@intel.com,
Pavel.Tatashin@microsoft.com, david@redhat.com,
yasu.isimatu@gmail.com, logang@deltatee.com,
dave.jiang@intel.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, Oscar Salvador <osalvador@suse.de>
Subject: Re: [RFC PATCH 2/3] mm/memory_hotplug: Create __shrink_pages and move it to offline_pages
Date: Thu, 16 Aug 2018 13:32:01 -0400 [thread overview]
Message-ID: <20180816173201.GC28097@redhat.com> (raw)
In-Reply-To: <20180816145849.GA17638@techadventures.net>
On Thu, Aug 16, 2018 at 04:58:49PM +0200, Oscar Salvador wrote:
> On Thu, Aug 09, 2018 at 12:58:21PM -0400, Jerome Glisse wrote:
> > I agree, i never thought about that before. Looking at existing resource
> > management i think the simplest solution would be to use a refcount on the
> > resources instead of the IORESOURCE_BUSY flags.
> >
> > So when you release resource as part of hotremove you would only dec the
> > refcount and a resource is not busy only when refcount is zero.
> >
> > Just the idea i had in mind. Right now i am working on other thing, Oscar
> > is this something you would like to work on ? Feel free to come up with
> > something better than my first idea :)
>
> So, I thought a bit about this.
> First I talked a bit with Jerome about the refcount idea.
> The problem with reconverting this to refcount is that it is too intrusive,
> and I think it is not really needed.
>
> I then thought about defining a new flag, something like
>
> #define IORESOURCE_NO_HOTREMOVE xxx
>
> but we ran out of bits for the flag field.
>
> I then thought about doing something like:
>
> struct resource {
> resource_size_t start;
> resource_size_t end;
> const char *name;
> unsigned long flags;
> unsigned long desc;
> struct resource *parent, *sibling, *child;
> #ifdef CONFIG_MEMORY_HOTREMOVE
> bool device_managed;
> #endif
> };
>
> but it is just too awful, not needed, and bytes consuming.
Agree the above is ugly.
>
> The only idea I had left is:
>
> register_memory_resource(), which defines a new resource for the added memory-chunk
> is only called from add_memory().
> This function is only being hit when we add memory-chunks.
>
> HMM/devm gets the resources their own way, calling devm_request_mem_region().
>
> So resources that are requested from HMM/devm, have the following flags:
>
> (IORESOURCE_MEM|IORESOURCE_BUSY)
>
> while resources that are requested via mem-hotplug have:
>
> (IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY)
>
> IORESOURCE_SYSTEM_RAM = (IORESOURCE_MEM|IORESOURCE_SYSRAM)
>
>
> release_mem_region_adjustable() is only being called from hot-remove path, so
> unless I am mistaken, all resources hitting that path should match IORESOURCE_SYSTEM_RAM.
>
> That leaves me with the idea that we could check for the resource->flags to contain IORESOURCE_SYSRAM,
> as I think it is only being set for memory-chunks that are added via memory-hot-add path.
>
> In case it is not, we know that that resource belongs to HMM/devm, so we can back off since
> they take care of releasing the resource via devm_release_mem_region.
>
> I am working on a RFC v2 containing this, but, Jerome, could you confirm above assumption, please?
I think you nail it. I am not 100% sure about devm as i have not
followed closely how persistent memory can be reported by ACPI. But
i am pretty sure it should never end up as SYSRAM.
Thank you for scratching your head on this :)
Cheers,
Jérôme
next prev parent reply other threads:[~2018-08-16 17:32 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-07 13:37 [RFC PATCH 0/3] Do not touch pages in remove_memory path osalvador
2018-08-07 13:37 ` [RFC PATCH 1/3] mm/memory_hotplug: Add nid parameter to arch_remove_memory osalvador
2018-08-07 13:37 ` [RFC PATCH 2/3] mm/memory_hotplug: Create __shrink_pages and move it to offline_pages osalvador
2018-08-07 13:52 ` Jerome Glisse
2018-08-07 14:54 ` David Hildenbrand
2018-08-07 15:19 ` Jerome Glisse
2018-08-07 15:28 ` David Hildenbrand
2018-08-07 20:48 ` Oscar Salvador
2018-08-07 22:13 ` Jerome Glisse
2018-08-08 7:38 ` Oscar Salvador
2018-08-08 7:45 ` David Hildenbrand
2018-08-08 7:56 ` Oscar Salvador
2018-08-08 8:08 ` David Hildenbrand
2018-08-08 13:42 ` Oscar Salvador
2018-08-08 17:55 ` Jerome Glisse
2018-08-08 21:29 ` Oscar Salvador
2018-08-09 7:50 ` Oscar Salvador
2018-08-09 7:52 ` Oscar Salvador
2018-08-08 7:51 ` David Hildenbrand
2018-08-08 8:00 ` Oscar Salvador
2018-08-07 14:59 ` Michal Hocko
2018-08-07 15:18 ` Jerome Glisse
2018-08-08 6:47 ` Michal Hocko
2018-08-08 16:58 ` Jerome Glisse
2018-08-08 21:28 ` Oscar Salvador
2018-08-09 8:24 ` Michal Hocko
2018-08-09 14:27 ` Jerome Glisse
2018-08-09 15:09 ` Michal Hocko
2018-08-09 16:58 ` Jerome Glisse
2018-08-09 20:50 ` Oscar Salvador
2018-08-16 14:58 ` Oscar Salvador
2018-08-16 17:32 ` Jerome Glisse [this message]
2018-08-08 9:45 ` Oscar Salvador
2018-08-08 17:33 ` Jerome Glisse
2018-08-07 13:37 ` [RFC PATCH 3/3] mm/memory_hotplug: Refactor shrink_zone/pgdat_span osalvador
2018-08-07 14:16 ` [RFC PATCH 0/3] Do not touch pages in remove_memory path David Hildenbrand
2018-08-07 14:19 ` Oscar Salvador
2018-08-07 14:20 ` David Hildenbrand
2018-08-07 14:28 ` Oscar Salvador
2018-08-07 14:41 ` David Hildenbrand
2018-08-07 14:52 ` Oscar Salvador
2018-08-15 14:05 ` Pavel Tatashin
2018-08-15 14:32 ` 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=20180816173201.GC28097@redhat.com \
--to=jglisse@redhat.com \
--cc=Pavel.Tatashin@microsoft.com \
--cc=akpm@linux-foundation.org \
--cc=dan.j.williams@intel.com \
--cc=dave.jiang@intel.com \
--cc=david@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=logang@deltatee.com \
--cc=mhocko@kernel.org \
--cc=osalvador@suse.de \
--cc=osalvador@techadventures.net \
--cc=yasu.isimatu@gmail.com \
/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).