From: Jerome Glisse <jglisse@redhat.com>
To: Dave Hansen <dave.hansen@intel.com>
Cc: Balbir Singh <bsingharora@gmail.com>,
akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, John Hubbard <jhubbard@nvidia.com>,
Dan Williams <dan.j.williams@intel.com>,
Ross Zwisler <ross.zwisler@linux.intel.com>
Subject: Re: [HMM v15 01/16] mm/free_hot_cold_page: catch ZONE_DEVICE pages
Date: Mon, 9 Jan 2017 12:58:56 -0500 [thread overview]
Message-ID: <20170109175856.GB3058@redhat.com> (raw)
In-Reply-To: <de3ede24-c883-aa6c-c7de-e76f1d0931bc@intel.com>
On Mon, Jan 09, 2017 at 09:00:34AM -0800, Dave Hansen wrote:
> On 01/09/2017 08:57 AM, Jerome Glisse wrote:
> > On Mon, Jan 09, 2017 at 08:21:25AM -0800, Dave Hansen wrote:
> >> On 01/09/2017 01:19 AM, Balbir Singh wrote:
> >>>> + /*
> >>>> + * This should never happen ! Page from ZONE_DEVICE always must have an
> >>>> + * active refcount. Complain about it and try to restore the refcount.
> >>>> + */
> >>>> + if (is_zone_device_page(page)) {
> >>>> + VM_BUG_ON_PAGE(is_zone_device_page(page), page);
> >>> This can be VM_BUG_ON_PAGE(1, page), hopefully the compiler does the right thing
> >>> here. I suspect this should be a BUG_ON, independent of CONFIG_DEBUG_VM
> >> BUG_ON() means "kill the machine dead". Do we really want a guaranteed
> >> dead machine if someone screws up their refcounting?
> > VM_BUG_ON_PAGE ok with you ? It is just a safety net, i can simply drop that
> > patch if people have too much feeling about it.
>
> Enough distros turn on DEBUG_VM that there's basically no difference
> between VM_BUG_ON() and BUG_ON().
>
> I also think it would be much nicer if you buried the check in the
> allocator in a slow path somewhere instead of sticking it in one of the
> hottest paths in the whole kernel.
Well i will just drop that patch then. The point was to catch error
early on before anything happen. This is just a safety net so not
fundamental.
Cheers,
Jérôme
next prev parent reply other threads:[~2017-01-09 17:59 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-06 16:46 [HMM v15 00/16] HMM (Heterogeneous Memory Management) v15 Jérôme Glisse
2017-01-06 16:46 ` [HMM v15 01/16] mm/free_hot_cold_page: catch ZONE_DEVICE pages Jérôme Glisse
2017-01-09 9:19 ` Balbir Singh
2017-01-09 16:21 ` Dave Hansen
2017-01-09 16:57 ` Jerome Glisse
2017-01-09 17:00 ` Dave Hansen
2017-01-09 17:58 ` Jerome Glisse [this message]
2017-01-06 16:46 ` [HMM v15 02/16] mm/memory/hotplug: convert device bool to int to allow for more flags v2 Jérôme Glisse
2017-01-06 16:46 ` [HMM v15 03/16] mm/ZONE_DEVICE/devmem_pages_remove: allow early removal of device memory Jérôme Glisse
2017-01-06 17:58 ` Dan Williams
2017-01-06 16:46 ` [HMM v15 04/16] mm/ZONE_DEVICE/free-page: callback when page is freed Jérôme Glisse
2017-01-06 16:46 ` [HMM v15 05/16] mm/ZONE_DEVICE/unaddressable: add support for un-addressable device memory v2 Jérôme Glisse
2017-01-06 16:46 ` [HMM v15 06/16] mm/ZONE_DEVICE/x86: add support for un-addressable device memory Jérôme Glisse
2017-01-06 16:46 ` [HMM v15 07/16] mm/hmm: heterogeneous memory management (HMM for short) Jérôme Glisse
2017-01-06 16:46 ` [HMM v15 08/16] mm/hmm/mirror: mirror process address space on device with HMM helpers Jérôme Glisse
2017-01-06 16:46 ` [HMM v15 09/16] mm/hmm/mirror: helper to snapshot CPU page table Jérôme Glisse
2017-01-06 16:46 ` [HMM v15 10/16] mm/hmm/mirror: device page fault handler Jérôme Glisse
2017-01-06 16:46 ` [HMM v15 11/16] mm/hmm/migrate: support un-addressable ZONE_DEVICE page in migration Jérôme Glisse
2017-01-06 16:46 ` [HMM v15 12/16] mm/hmm/migrate: add new boolean copy flag to migratepage() callback Jérôme Glisse
2017-01-06 16:46 ` [HMM v15 13/16] mm/hmm/migrate: new memory migration helper for use with device memory v2 Jérôme Glisse
2017-01-06 16:46 ` David Nellans
2017-01-06 17:13 ` Jerome Glisse
2017-01-10 15:30 ` David Nellans
2017-01-10 16:58 ` Jerome Glisse
2017-01-06 16:46 ` [HMM v15 14/16] mm/hmm/migrate: optimize page map once in vma being migrated Jérôme Glisse
2017-01-06 16:46 ` [HMM v15 15/16] mm/hmm/devmem: device driver helper to hotplug ZONE_DEVICE memory Jérôme Glisse
2017-01-06 16:46 ` [HMM v15 16/16] mm/hmm/devmem: dummy HMM device as an helper for " Jérôme Glisse
2017-01-06 20:54 ` [HMM v15 00/16] HMM (Heterogeneous Memory Management) v15 Dave Hansen
2017-01-06 21:16 ` Jerome Glisse
2017-01-06 21:36 ` Jerome Glisse
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