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[PATCH 0/5] Cache coherent device memory (CDM) with HMM v4

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  [PATCH 0/5] Cache coherent device memory (CDM) with HMM v4 Jérôme Glisse <jglisse@redhat.com> - 2017-07-12 20:10 +0200
    [PATCH 5/5] mm/hmm: documents how device memory is accounted in rss and memcg Jérôme Glisse <jglisse@redhat.com> - 2017-07-12 20:10 +0200
    [PATCH 3/5] mm/memcontrol: allow to uncharge page without using page->lru field Jérôme Glisse <jglisse@redhat.com> - 2017-07-12 20:10 +0200
    [PATCH 4/5] mm/memcontrol: support MEMORY_DEVICE_PRIVATE and MEMORY_DEVICE_HOST v2 Jérôme Glisse <jglisse@redhat.com> - 2017-07-12 20:10 +0200
    Re: [PATCH 0/5] Cache coherent device memory (CDM) with HMM v4 Balbir Singh <bsingharora@gmail.com> - 2017-07-13 08:40 +0200
      Re: [PATCH 0/5] Cache coherent device memory (CDM) with HMM v4 Jerome Glisse <jglisse@redhat.com> - 2017-07-13 22:20 +0200

#1685948 — [PATCH 0/5] Cache coherent device memory (CDM) with HMM v4

Changes since v3:
  - change name to device host (s/DEVICE_PUBLIC/DEVICE_HOST/)
  - added comments about how such memory is accounted (rss and memcg)
  - added a documentation patch (to explain rss and memcg choice)
  - add proper include to migrate.c and drop #if/#endif
  - fix missing #if/#endif so this works even if DEVICE_PRIVATE is
    not enabled

Git tree:
https://cgit.freedesktop.org/~glisse/linux/log/?h=hmm-cdm-v4


Cache coherent device memory apply to architecture with system bus
like CAPI or CCIX. Device connected to such system bus can expose
their memory to the system and allow cache coherent access to it
from the CPU.

Even if for all intent and purposes device memory behave like regular
memory, we still want to manage it in isolation from regular memory.
Several reasons for that, first and foremost this memory is less
reliable than regular memory if the device hangs because of invalid
commands we can loose access to device memory. Second CPU access to
this memory is expected to be slower than to regular memory. Third
having random memory into device means that some of the bus bandwith
wouldn't be available to the device but would be use by CPU access.

This is why we want to manage such memory in isolation from regular
memory. Kernel should not try to use this memory even as last resort
when running out of memory, at least for now.

This patchset add a new type of ZONE_DEVICE memory (DEVICE_HOST)
that is use to represent CDM memory. This patchset build on top of
the HMM patchset that already introduce a new type of ZONE_DEVICE
memory for private device memory (see HMM patchset).

The end result is that with this patchset if a device is in use in
a process you might have private anonymous memory or file back
page memory using ZONE_DEVICE (DEVICE_HOST). Thus care must be
taken to not overwritte lru fields of such pages.

Hence all core mm changes are done to address assumption that any
process memory is back by a regular struct page that is part of
the lru. ZONE_DEVICE page are not on the lru and the lru pointer
of struct page are use to store device specific informations.

Thus this patchset update all code path that would make assumptions
about lruness of a process page.

patch 01 - add DEVICE_HOST type to ZONE_DEVICE (all core mm changes)
patch 02 - add an helper to HMM for hotplug of CDM memory
patch 03 - preparatory patch for memory controller changes (memch)
patch 04 - update memory controller to properly handle
           ZONE_DEVICE pages when uncharging
patch 05 - documentation patch

Previous posting:
v1 https://lkml.org/lkml/2017/4/7/638
v2 https://lwn.net/Articles/725412/
v3 https://lwn.net/Articles/727114/

Jérôme Glisse (5):
  mm/device-host-memory: device memory cache coherent with CPU v3
  mm/hmm: add new helper to hotplug CDM memory region v2
  mm/memcontrol: allow to uncharge page without using page->lru field
  mm/memcontrol: support MEMORY_DEVICE_PRIVATE and MEMORY_DEVICE_HOST v2
  mm/hmm: documents how device memory is accounted in rss and memcg

 Documentation/vm/hmm.txt |  40 ++++++++
 fs/proc/task_mmu.c       |   2 +-
 include/linux/hmm.h      |   7 +-
 include/linux/ioport.h   |   1 +
 include/linux/memremap.h |  21 +++++
 include/linux/mm.h       |  20 ++--
 kernel/memremap.c        |  17 +++-
 mm/Kconfig               |  11 +++
 mm/gup.c                 |   7 ++
 mm/hmm.c                 |  89 ++++++++++++++++--
 mm/madvise.c             |   2 +-
 mm/memcontrol.c          | 231 ++++++++++++++++++++++++++++++-----------------
 mm/memory.c              |  46 +++++++++-
 mm/migrate.c             |  57 +++++++-----
 mm/swap.c                |  11 +++
 15 files changed, 431 insertions(+), 131 deletions(-)

-- 
2.13.0

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#1685949 — [PATCH 5/5] mm/hmm: documents how device memory is accounted in rss and memcg

For now we account device memory exactly like a regular page in
respect to rss counters and memory cgroup. We do this so that any
existing application that starts using device memory without knowing
about it will keep running unimpacted. This also simplify migration
code.

We will likely revisit this choice once we gain more experience with
how device memory is use and how it impacts overall memory resource
management. For now we believe this is a good enough choice.

Note that device memory can not be pin. Nor by device driver, nor
by GUP thus device memory can always be free and unaccounted when
a process exit.

Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
---
 Documentation/vm/hmm.txt | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/Documentation/vm/hmm.txt b/Documentation/vm/hmm.txt
index 192dcdb38bd1..4d3aac9f4a5d 100644
--- a/Documentation/vm/hmm.txt
+++ b/Documentation/vm/hmm.txt
@@ -15,6 +15,15 @@ section present the new migration helper that allow to leverage the device DMA
 engine.
 
 
+1) Problems of using device specific memory allocator:
+2) System bus, device memory characteristics
+3) Share address space and migration
+4) Address space mirroring implementation and API
+5) Represent and manage device memory from core kernel point of view
+6) Migrate to and from device memory
+7) Memory cgroup (memcg) and rss accounting
+
+
 -------------------------------------------------------------------------------
 
 1) Problems of using device specific memory allocator:
@@ -342,3 +351,34 @@ that happens then the finalize_and_map() can catch any pages that was not
 migrated. Note those page were still copied to new page and thus we wasted
 bandwidth but this is considered as a rare event and a price that we are
 willing to pay to keep all the code simpler.
+
+
+-------------------------------------------------------------------------------
+
+7) Memory cgroup (memcg) and rss accounting
+
+For now device memory is accounted as any regular page in rss counters (either
+anonymous if device page is use for anonymous, file if device page is use for
+file back page or shmem if device page is use for share memory). This is a
+deliberate choice to keep existing application that might start using device
+memory without knowing about it to keep runing unimpacted.
+
+Drawbacks is that OOM killer might kill an application using a lot of device
+memory and not a lot of regular system memory and thus not freeing much system
+memory. We want to gather more real world experience on how application and
+system react under memory pressure in the presence of device memory before
+deciding to account device memory differently.
+
+
+Same decision was made for memory cgroup. Device memory page are accounted
+against same memory cgroup a regular page would be accounted to. This does
+simplify migration to and from device memory. This also means that migration
+back from device memory to regular memory can not fail because it would
+go above memory cgroup limit. We might revisit this choice latter on once we
+get more experience in how device memory is use and its impact on memory
+resource control.
+
+
+Note that device memory can never be pin nor by device driver nor through GUP
+and thus such memory is always free upon process exit. Or when last reference
+is drop in case of share memory or file back memory.
-- 
2.13.0

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#1685950 — [PATCH 3/5] mm/memcontrol: allow to uncharge page without using page->lru field

HMM pages (private or host device pages) are ZONE_DEVICE page and
thus you can not use page->lru fields of those pages. This patch
re-arrange the uncharge to allow single page to be uncharge without
modifying the lru field of the struct page.

There is no change to memcontrol logic, it is the same as it was
before this patch.

Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: cgroups@vger.kernel.org
---
 mm/memcontrol.c | 168 +++++++++++++++++++++++++++++++-------------------------
 1 file changed, 92 insertions(+), 76 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 3df3c04d73ab..c709fdceac13 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5509,48 +5509,102 @@ void mem_cgroup_cancel_charge(struct page *page, struct mem_cgroup *memcg,
 	cancel_charge(memcg, nr_pages);
 }
 
-static void uncharge_batch(struct mem_cgroup *memcg, unsigned long pgpgout,
-			   unsigned long nr_anon, unsigned long nr_file,
-			   unsigned long nr_kmem, unsigned long nr_huge,
-			   unsigned long nr_shmem, struct page *dummy_page)
+struct uncharge_gather {
+	struct mem_cgroup *memcg;
+	unsigned long pgpgout;
+	unsigned long nr_anon;
+	unsigned long nr_file;
+	unsigned long nr_kmem;
+	unsigned long nr_huge;
+	unsigned long nr_shmem;
+	struct page *dummy_page;
+};
+
+static inline void uncharge_gather_clear(struct uncharge_gather *ug)
 {
-	unsigned long nr_pages = nr_anon + nr_file + nr_kmem;
+	memset(ug, 0, sizeof(*ug));
+}
+
+static void uncharge_batch(const struct uncharge_gather *ug)
+{
+	unsigned long nr_pages = ug->nr_anon + ug->nr_file + ug->nr_kmem;
 	unsigned long flags;
 
-	if (!mem_cgroup_is_root(memcg)) {
-		page_counter_uncharge(&memcg->memory, nr_pages);
+	if (!mem_cgroup_is_root(ug->memcg)) {
+		page_counter_uncharge(&ug->memcg->memory, nr_pages);
 		if (do_memsw_account())
-			page_counter_uncharge(&memcg->memsw, nr_pages);
-		if (!cgroup_subsys_on_dfl(memory_cgrp_subsys) && nr_kmem)
-			page_counter_uncharge(&memcg->kmem, nr_kmem);
-		memcg_oom_recover(memcg);
+			page_counter_uncharge(&ug->memcg->memsw, nr_pages);
+		if (!cgroup_subsys_on_dfl(memory_cgrp_subsys) && ug->nr_kmem)
+			page_counter_uncharge(&ug->memcg->kmem, ug->nr_kmem);
+		memcg_oom_recover(ug->memcg);
 	}
 
 	local_irq_save(flags);
-	__this_cpu_sub(memcg->stat->count[MEMCG_RSS], nr_anon);
-	__this_cpu_sub(memcg->stat->count[MEMCG_CACHE], nr_file);
-	__this_cpu_sub(memcg->stat->count[MEMCG_RSS_HUGE], nr_huge);
-	__this_cpu_sub(memcg->stat->count[NR_SHMEM], nr_shmem);
-	__this_cpu_add(memcg->stat->events[PGPGOUT], pgpgout);
-	__this_cpu_add(memcg->stat->nr_page_events, nr_pages);
-	memcg_check_events(memcg, dummy_page);
+	__this_cpu_sub(ug->memcg->stat->count[MEMCG_RSS], ug->nr_anon);
+	__this_cpu_sub(ug->memcg->stat->count[MEMCG_CACHE], ug->nr_file);
+	__this_cpu_sub(ug->memcg->stat->count[MEMCG_RSS_HUGE], ug->nr_huge);
+	__this_cpu_sub(ug->memcg->stat->count[NR_SHMEM], ug->nr_shmem);
+	__this_cpu_add(ug->memcg->stat->events[PGPGOUT], ug->pgpgout);
+	__this_cpu_add(ug->memcg->stat->nr_page_events, nr_pages);
+	memcg_check_events(ug->memcg, ug->dummy_page);
 	local_irq_restore(flags);
 
-	if (!mem_cgroup_is_root(memcg))
-		css_put_many(&memcg->css, nr_pages);
+	if (!mem_cgroup_is_root(ug->memcg))
+		css_put_many(&ug->memcg->css, nr_pages);
+}
+
+static void uncharge_page(struct page *page, struct uncharge_gather *ug)
+{
+	VM_BUG_ON_PAGE(PageLRU(page), page);
+	VM_BUG_ON_PAGE(!PageHWPoison(page) && page_count(page), page);
+
+	if (!page->mem_cgroup)
+		return;
+
+	/*
+	 * Nobody should be changing or seriously looking at
+	 * page->mem_cgroup at this point, we have fully
+	 * exclusive access to the page.
+	 */
+
+	if (ug->memcg != page->mem_cgroup) {
+		if (ug->memcg) {
+			uncharge_batch(ug);
+			uncharge_gather_clear(ug);
+		}
+		ug->memcg = page->mem_cgroup;
+	}
+
+	if (!PageKmemcg(page)) {
+		unsigned int nr_pages = 1;
+
+		if (PageTransHuge(page)) {
+			nr_pages <<= compound_order(page);
+			ug->nr_huge += nr_pages;
+		}
+		if (PageAnon(page))
+			ug->nr_anon += nr_pages;
+		else {
+			ug->nr_file += nr_pages;
+			if (PageSwapBacked(page))
+				ug->nr_shmem += nr_pages;
+		}
+		ug->pgpgout++;
+	} else {
+		ug->nr_kmem += 1 << compound_order(page);
+		__ClearPageKmemcg(page);
+	}
+
+	ug->dummy_page = page;
+	page->mem_cgroup = NULL;
 }
 
 static void uncharge_list(struct list_head *page_list)
 {
-	struct mem_cgroup *memcg = NULL;
-	unsigned long nr_shmem = 0;
-	unsigned long nr_anon = 0;
-	unsigned long nr_file = 0;
-	unsigned long nr_huge = 0;
-	unsigned long nr_kmem = 0;
-	unsigned long pgpgout = 0;
+	struct uncharge_gather ug;
 	struct list_head *next;
-	struct page *page;
+
+	uncharge_gather_clear(&ug);
 
 	/*
 	 * Note that the list can be a single page->lru; hence the
@@ -5558,57 +5612,16 @@ static void uncharge_list(struct list_head *page_list)
 	 */
 	next = page_list->next;
 	do {
+		struct page *page;
+
 		page = list_entry(next, struct page, lru);
 		next = page->lru.next;
 
-		VM_BUG_ON_PAGE(PageLRU(page), page);
-		VM_BUG_ON_PAGE(!PageHWPoison(page) && page_count(page), page);
-
-		if (!page->mem_cgroup)
-			continue;
-
-		/*
-		 * Nobody should be changing or seriously looking at
-		 * page->mem_cgroup at this point, we have fully
-		 * exclusive access to the page.
-		 */
-
-		if (memcg != page->mem_cgroup) {
-			if (memcg) {
-				uncharge_batch(memcg, pgpgout, nr_anon, nr_file,
-					       nr_kmem, nr_huge, nr_shmem, page);
-				pgpgout = nr_anon = nr_file = nr_kmem = 0;
-				nr_huge = nr_shmem = 0;
-			}
-			memcg = page->mem_cgroup;
-		}
-
-		if (!PageKmemcg(page)) {
-			unsigned int nr_pages = 1;
-
-			if (PageTransHuge(page)) {
-				nr_pages <<= compound_order(page);
-				nr_huge += nr_pages;
-			}
-			if (PageAnon(page))
-				nr_anon += nr_pages;
-			else {
-				nr_file += nr_pages;
-				if (PageSwapBacked(page))
-					nr_shmem += nr_pages;
-			}
-			pgpgout++;
-		} else {
-			nr_kmem += 1 << compound_order(page);
-			__ClearPageKmemcg(page);
-		}
-
-		page->mem_cgroup = NULL;
+		uncharge_page(page, &ug);
 	} while (next != page_list);
 
-	if (memcg)
-		uncharge_batch(memcg, pgpgout, nr_anon, nr_file,
-			       nr_kmem, nr_huge, nr_shmem, page);
+	if (ug.memcg)
+		uncharge_batch(&ug);
 }
 
 /**
@@ -5620,6 +5633,8 @@ static void uncharge_list(struct list_head *page_list)
  */
 void mem_cgroup_uncharge(struct page *page)
 {
+	struct uncharge_gather ug;
+
 	if (mem_cgroup_disabled())
 		return;
 
@@ -5627,8 +5642,9 @@ void mem_cgroup_uncharge(struct page *page)
 	if (!page->mem_cgroup)
 		return;
 
-	INIT_LIST_HEAD(&page->lru);
-	uncharge_list(&page->lru);
+	uncharge_gather_clear(&ug);
+	uncharge_page(page, &ug);
+	uncharge_batch(&ug);
 }
 
 /**
-- 
2.13.0

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#1685951 — [PATCH 4/5] mm/memcontrol: support MEMORY_DEVICE_PRIVATE and MEMORY_DEVICE_HOST v2

HMM pages (private or host device pages) are ZONE_DEVICE page and
thus need special handling when it comes to lru or refcount. This
patch make sure that memcontrol properly handle those when it face
them. Those pages are use like regular pages in a process address
space either as anonymous page or as file back page. So from memcg
point of view we want to handle them like regular page for now at
least.

Changed since v1:
  - s/public/host
  - add comments explaining how device memory behave and why

Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: cgroups@vger.kernel.org
---
 kernel/memremap.c |  2 ++
 mm/memcontrol.c   | 63 ++++++++++++++++++++++++++++++++++++++++++++++++++-----
 2 files changed, 60 insertions(+), 5 deletions(-)

diff --git a/kernel/memremap.c b/kernel/memremap.c
index 8e19f6513dfd..165818363e6a 100644
--- a/kernel/memremap.c
+++ b/kernel/memremap.c
@@ -479,6 +479,8 @@ void put_zone_device_private_or_host_page(struct page *page)
 		__ClearPageActive(page);
 		__ClearPageWaiters(page);
 
+		mem_cgroup_uncharge(page);
+
 		page->pgmap->page_free(page, page->pgmap->data);
 	}
 	else if (!count)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index c709fdceac13..f8a961c7b3a0 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4391,12 +4391,13 @@ enum mc_target_type {
 	MC_TARGET_NONE = 0,
 	MC_TARGET_PAGE,
 	MC_TARGET_SWAP,
+	MC_TARGET_DEVICE,
 };
 
 static struct page *mc_handle_present_pte(struct vm_area_struct *vma,
 						unsigned long addr, pte_t ptent)
 {
-	struct page *page = vm_normal_page(vma, addr, ptent);
+	struct page *page = _vm_normal_page(vma, addr, ptent, true);
 
 	if (!page || !page_mapped(page))
 		return NULL;
@@ -4407,13 +4408,20 @@ static struct page *mc_handle_present_pte(struct vm_area_struct *vma,
 		if (!(mc.flags & MOVE_FILE))
 			return NULL;
 	}
-	if (!get_page_unless_zero(page))
+	if (is_device_host_page(page)) {
+		/*
+		 * MEMORY_DEVICE_HOST means ZONE_DEVICE page and which have a
+		 * refcount of 1 when free (unlike normal page)
+		 */
+		if (!page_ref_add_unless(page, 1, 1))
+			return NULL;
+	} else if (!get_page_unless_zero(page))
 		return NULL;
 
 	return page;
 }
 
-#ifdef CONFIG_SWAP
+#if defined(CONFIG_SWAP) || defined(CONFIG_DEVICE_PRIVATE)
 static struct page *mc_handle_swap_pte(struct vm_area_struct *vma,
 			pte_t ptent, swp_entry_t *entry)
 {
@@ -4422,6 +4430,23 @@ static struct page *mc_handle_swap_pte(struct vm_area_struct *vma,
 
 	if (!(mc.flags & MOVE_ANON) || non_swap_entry(ent))
 		return NULL;
+
+	/*
+	 * Handle MEMORY_DEVICE_PRIVATE which are ZONE_DEVICE page belonging to
+	 * a device and because they are not accessible by CPU they are store
+	 * as special swap entry in the CPU page table.
+	 */
+	if (is_device_private_entry(ent)) {
+		page = device_private_entry_to_page(ent);
+		/*
+		 * MEMORY_DEVICE_PRIVATE means ZONE_DEVICE page and which have
+		 * a refcount of 1 when free (unlike normal page)
+		 */
+		if (!page_ref_add_unless(page, 1, 1))
+			return NULL;
+		return page;
+	}
+
 	/*
 	 * Because lookup_swap_cache() updates some statistics counter,
 	 * we call find_get_page() with swapper_space directly.
@@ -4582,6 +4607,13 @@ static int mem_cgroup_move_account(struct page *page,
  *   2(MC_TARGET_SWAP): if the swap entry corresponding to this pte is a
  *     target for charge migration. if @target is not NULL, the entry is stored
  *     in target->ent.
+ *   3(MC_TARGET_DEVICE): like MC_TARGET_PAGE  but page is MEMORY_DEVICE_HOST
+ *     or MEMORY_DEVICE_PRIVATE (so ZONE_DEVICE page and thus not on the lru).
+ *     For now we such page is charge like a regular page would be as for all
+ *     intent and purposes it is just special memory taking the place of a
+ *     regular page. See Documentations/vm/hmm.txt and include/linux/hmm.h for
+ *     more informations on this type of memory how it is use and why it is
+ *     charge like this.
  *
  * Called with pte lock held.
  */
@@ -4610,6 +4642,9 @@ static enum mc_target_type get_mctgt_type(struct vm_area_struct *vma,
 		 */
 		if (page->mem_cgroup == mc.from) {
 			ret = MC_TARGET_PAGE;
+			if (is_device_private_page(page) ||
+			    is_device_host_page(page))
+				ret = MC_TARGET_DEVICE;
 			if (target)
 				target->page = page;
 		}
@@ -4669,6 +4704,11 @@ static int mem_cgroup_count_precharge_pte_range(pmd_t *pmd,
 
 	ptl = pmd_trans_huge_lock(pmd, vma);
 	if (ptl) {
+		/*
+		 * Note their can not be MC_TARGET_DEVICE for now as we do not
+		 * support transparent huge page with MEMORY_DEVICE_HOST or
+		 * MEMORY_DEVICE_PRIVATE but this might change.
+		 */
 		if (get_mctgt_type_thp(vma, addr, *pmd, NULL) == MC_TARGET_PAGE)
 			mc.precharge += HPAGE_PMD_NR;
 		spin_unlock(ptl);
@@ -4884,6 +4924,14 @@ static int mem_cgroup_move_charge_pte_range(pmd_t *pmd,
 				putback_lru_page(page);
 			}
 			put_page(page);
+		} else if (target_type == MC_TARGET_DEVICE) {
+			page = target.page;
+			if (!mem_cgroup_move_account(page, true,
+						     mc.from, mc.to)) {
+				mc.precharge -= HPAGE_PMD_NR;
+				mc.moved_charge += HPAGE_PMD_NR;
+			}
+			put_page(page);
 		}
 		spin_unlock(ptl);
 		return 0;
@@ -4895,12 +4943,16 @@ static int mem_cgroup_move_charge_pte_range(pmd_t *pmd,
 	pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
 	for (; addr != end; addr += PAGE_SIZE) {
 		pte_t ptent = *(pte++);
+		bool device = false;
 		swp_entry_t ent;
 
 		if (!mc.precharge)
 			break;
 
 		switch (get_mctgt_type(vma, addr, ptent, &target)) {
+		case MC_TARGET_DEVICE:
+			device = true;
+			/* fall through */
 		case MC_TARGET_PAGE:
 			page = target.page;
 			/*
@@ -4911,7 +4963,7 @@ static int mem_cgroup_move_charge_pte_range(pmd_t *pmd,
 			 */
 			if (PageTransCompound(page))
 				goto put;
-			if (isolate_lru_page(page))
+			if (!device && isolate_lru_page(page))
 				goto put;
 			if (!mem_cgroup_move_account(page, false,
 						mc.from, mc.to)) {
@@ -4919,7 +4971,8 @@ static int mem_cgroup_move_charge_pte_range(pmd_t *pmd,
 				/* we uncharge from mc.from later. */
 				mc.moved_charge++;
 			}
-			putback_lru_page(page);
+			if (!device)
+				putback_lru_page(page);
 put:			/* get_mctgt_type() gets the page */
 			put_page(page);
 			break;
-- 
2.13.0

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#1686287

On Wed, 12 Jul 2017 14:06:02 -0400
Jérôme Glisse <jglisse@redhat.com> wrote:

> Changes since v3:
>   - change name to device host (s/DEVICE_PUBLIC/DEVICE_HOST/)

I think you've mis-interpreted what Dan said

The message @
http://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1441839.html
states

"I was suggesting MEMORY_DEVICE_HOST for persistent memory and
MEMORY_DEVICE_PUBLIC as you want for CDM."

I guess we get to keep DEVICE_PUBLIC and move persistent memory
to MEMORY_DEVICE_HOST

Balbir Singh

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#1686879

On Thu, Jul 13, 2017 at 04:32:28PM +1000, Balbir Singh wrote:
> On Wed, 12 Jul 2017 14:06:02 -0400
> Jérôme Glisse <jglisse@redhat.com> wrote:
> 
> > Changes since v3:
> >   - change name to device host (s/DEVICE_PUBLIC/DEVICE_HOST/)
> 
> I think you've mis-interpreted what Dan said
> 
> The message @
> http://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1441839.html
> states
> 
> "I was suggesting MEMORY_DEVICE_HOST for persistent memory and
> MEMORY_DEVICE_PUBLIC as you want for CDM."

Oh i missed that email :( is was lost in long spam thread in my inbox.
Well i will likely repost a new version of HMM-CDM and with updated
name then.

Jérôme

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