From: Michal Hocko <mhocko@kernel.org>
To: Jerome Glisse <jglisse@redhat.com>
Cc: osalvador@techadventures.net, akpm@linux-foundation.org,
dan.j.williams@intel.com, pasha.tatashin@oracle.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, 9 Aug 2018 10:24:15 +0200 [thread overview]
Message-ID: <20180809082415.GB24884@dhcp22.suse.cz> (raw)
In-Reply-To: <20180808165814.GB3429@redhat.com>
On Wed 08-08-18 12:58:15, Jerome Glisse wrote:
> On Wed, Aug 08, 2018 at 08:47:58AM +0200, Michal Hocko wrote:
> > On Tue 07-08-18 11:18:10, Jerome Glisse wrote:
> > > On Tue, Aug 07, 2018 at 04:59:00PM +0200, Michal Hocko wrote:
> > > > On Tue 07-08-18 09:52:21, Jerome Glisse wrote:
> > > > > On Tue, Aug 07, 2018 at 03:37:56PM +0200, osalvador@techadventures.net wrote:
> > > > > > From: Oscar Salvador <osalvador@suse.de>
> > > > >
> > > > > [...]
> > > > >
> > > > > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> > > > > > index 9bd629944c91..e33555651e46 100644
> > > > > > --- a/mm/memory_hotplug.c
> > > > > > +++ b/mm/memory_hotplug.c
> > > > >
> > > > > [...]
> > > > >
> > > > > > /**
> > > > > > * __remove_pages() - remove sections of pages from a zone
> > > > > > - * @zone: zone from which pages need to be removed
> > > > > > + * @nid: node which pages belong to
> > > > > > * @phys_start_pfn: starting pageframe (must be aligned to start of a section)
> > > > > > * @nr_pages: number of pages to remove (must be multiple of section size)
> > > > > > * @altmap: alternative device page map or %NULL if default memmap is used
> > > > > > @@ -548,7 +557,7 @@ static int __remove_section(struct zone *zone, struct mem_section *ms,
> > > > > > * sure that pages are marked reserved and zones are adjust properly by
> > > > > > * calling offline_pages().
> > > > > > */
> > > > > > -int __remove_pages(struct zone *zone, unsigned long phys_start_pfn,
> > > > > > +int __remove_pages(int nid, unsigned long phys_start_pfn,
> > > > > > unsigned long nr_pages, struct vmem_altmap *altmap)
> > > > > > {
> > > > > > unsigned long i;
> > > > > > @@ -556,10 +565,9 @@ int __remove_pages(struct zone *zone, unsigned long phys_start_pfn,
> > > > > > int sections_to_remove, ret = 0;
> > > > > >
> > > > > > /* In the ZONE_DEVICE case device driver owns the memory region */
> > > > > > - if (is_dev_zone(zone)) {
> > > > > > - if (altmap)
> > > > > > - map_offset = vmem_altmap_offset(altmap);
> > > > > > - } else {
> > > > > > + if (altmap)
> > > > > > + map_offset = vmem_altmap_offset(altmap);
> > > > > > + else {
> > > > >
> > > > > This will break ZONE_DEVICE at least for HMM. While i think that
> > > > > altmap -> ZONE_DEVICE (ie altmap imply ZONE_DEVICE) the reverse
> > > > > is not true ie ZONE_DEVICE does not necessarily imply altmap. So
> > > > > with the above changes you change the expected behavior.
> > > >
> > > > Could you be more specific what is the expected behavior here?
> > > > Is this about calling release_mem_region_adjustable? Why does is it not
> > > > suitable for zone device ranges?
> > >
> > > Correct, you should not call release_mem_region_adjustable() the device
> > > region is not part of regular iomem resource as it might not necessarily
> > > be enumerated through known ways to the kernel (ie only the device driver
> > > can discover the region and core kernel do not know about it).
> >
> > If there is no region registered with the range then the call should be
> > mere nop, no? So why do we have to special case?
>
> IIRC this is because you can not release the resource ie the resource
> is still own by the device driver even if you hotremove the memory.
> The device driver might still be using the resource without struct page.
But then it seems to be a property of a device rather than zone_device,
no? If there are devices which want to preserve the resource then they
should tell that. Doing that unconditionally for all zone_device users
seems just wrong.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2018-08-09 8:24 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 [this message]
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
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
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