Re: [PATCH v4 09/10] iommu: observability of the IOMMU allocations

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On 2024-02-07 5:41 pm, Pasha Tatashin wrote:
Add NR_IOMMU_PAGES into node_stat_item that counts number of pages
that are allocated by the IOMMU subsystem.

The allocations can be view per-node via:
/sys/devices/system/node/nodeN/vmstat.

For example:

$ grep iommu /sys/devices/system/node/node*/vmstat
/sys/devices/system/node/node0/vmstat:nr_iommu_pages 106025
/sys/devices/system/node/node1/vmstat:nr_iommu_pages 3464

The value is in page-count, therefore, in the above example
the iommu allocations amount to ~428M.

Signed-off-by: Pasha Tatashin <pasha.tatashin@xxxxxxxxxx>
Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
Tested-by: Bagas Sanjaya <bagasdotme@xxxxxxxxx>
---
  drivers/iommu/iommu-pages.h | 30 ++++++++++++++++++++++++++++++
  include/linux/mmzone.h      |  3 +++
  mm/vmstat.c                 |  3 +++
  3 files changed, 36 insertions(+)

diff --git a/drivers/iommu/iommu-pages.h b/drivers/iommu/iommu-pages.h
index c412d0aaa399..7336f976b641 100644
--- a/drivers/iommu/iommu-pages.h
+++ b/drivers/iommu/iommu-pages.h
@@ -17,6 +17,30 @@
   * state can be rather large, i.e. multiple gigabytes in size.
   */
+/**
+ * __iommu_alloc_account - account for newly allocated page.
+ * @page: head struct page of the page.
+ * @order: order of the page
+ */
+static inline void __iommu_alloc_account(struct page *page, int order)
+{
+	const long pgcnt = 1l << order;
+
+	mod_node_page_state(page_pgdat(page), NR_IOMMU_PAGES, pgcnt);
+}
+
+/**
+ * __iommu_free_account - account a page that is about to be freed.
+ * @page: head struct page of the page.
+ * @order: order of the page
+ */
+static inline void __iommu_free_account(struct page *page, int order)
+{
+	const long pgcnt = 1l << order;
+
+	mod_node_page_state(page_pgdat(page), NR_IOMMU_PAGES, -pgcnt);
+}
+
  /**
   * __iommu_alloc_pages_node - allocate a zeroed page of a given order from
   * specific NUMA node.
@@ -35,6 +59,8 @@ static inline struct page *__iommu_alloc_pages_node(int nid, gfp_t gfp,
  	if (unlikely(!page))
  		return NULL;
+ __iommu_alloc_account(page, order);
+
  	return page;
  }
@@ -53,6 +79,8 @@ static inline struct page *__iommu_alloc_pages(gfp_t gfp, int order)
  	if (unlikely(!page))
  		return NULL;
+ __iommu_alloc_account(page, order);
+
  	return page;
  }
@@ -89,6 +117,7 @@ static inline void __iommu_free_pages(struct page *page, int order)
  	if (!page)
  		return;
+ __iommu_free_account(page, order);
  	__free_pages(page, order);
  }
@@ -197,6 +226,7 @@ static inline void iommu_free_pages_list(struct list_head *page)
  		struct page *p = list_entry(page->prev, struct page, lru);
list_del(&p->lru);
+		__iommu_free_account(p, 0);

I'm keen to revive my patches to hook up freelist support in io-pgtable-arm, which would then mean a chance of higher-order GFP_COMP allocations coming back though this path - do you have any pointers for what I'd have to do here to make it work properly?

Thanks,
Robin.

  		put_page(p);
  	}
  }
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index a497f189d988..bb6bc504915a 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -203,6 +203,9 @@ enum node_stat_item {
  #endif
  	NR_PAGETABLE,		/* used for pagetables */
  	NR_SECONDARY_PAGETABLE, /* secondary pagetables, e.g. KVM pagetables */
+#ifdef CONFIG_IOMMU_SUPPORT
+	NR_IOMMU_PAGES,		/* # of pages allocated by IOMMU */
+#endif
  #ifdef CONFIG_SWAP
  	NR_SWAPCACHE,
  #endif
diff --git a/mm/vmstat.c b/mm/vmstat.c
index db79935e4a54..8507c497218b 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1242,6 +1242,9 @@ const char * const vmstat_text[] = {
  #endif
  	"nr_page_table_pages",
  	"nr_sec_page_table_pages",
+#ifdef CONFIG_IOMMU_SUPPORT
+	"nr_iommu_pages",
+#endif
  #ifdef CONFIG_SWAP
  	"nr_swapcached",
  #endif




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