On 24/10/2018 06:12, Matthew Wilcox wrote:
On Wed, Oct 24, 2018 at 12:34:55AM +0300, Igor Stoppa wrote:
The connection between each page and its vmap_area avoids more expensive
searches through the btree of vmap_areas.
Typo -- it's an rbtree.
ack
+++ b/include/linux/mm_types.h
@@ -87,13 +87,24 @@ struct page {
/* See page-flags.h for PAGE_MAPPING_FLAGS */
struct address_space *mapping;
pgoff_t index; /* Our offset within mapping. */
- /**
- * @private: Mapping-private opaque data.
- * Usually used for buffer_heads if PagePrivate.
- * Used for swp_entry_t if PageSwapCache.
- * Indicates order in the buddy system if PageBuddy.
- */
- unsigned long private;
+ union {
+ /**
+ * @private: Mapping-private opaque data.
+ * Usually used for buffer_heads if
+ * PagePrivate.
+ * Used for swp_entry_t if PageSwapCache.
+ * Indicates order in the buddy system if
+ * PageBuddy.
+ */
+ unsigned long private;
+ /**
+ * @area: reference to the containing area
+ * For pages that are mapped into a virtually
+ * contiguous area, avoids performing a more
+ * expensive lookup.
+ */
+ struct vmap_area *area;
+ };
Not like this. Make it part of a different struct in the existing union,
not a part of the pagecache struct. And there's no need to use ->private
explicitly.
Ok, I'll have a look at the googledoc you made
@@ -1747,6 +1750,10 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align,
if (!addr)
return NULL;
+ va = __find_vmap_area((unsigned long)addr);
+ for (i = 0; i < va->vm->nr_pages; i++)
+ va->vm->pages[i]->area = va;
I don't like it that you're calling this for _every_ vmalloc() caller
when most of them will never use this. Perhaps have page->va be initially
NULL and then cache the lookup in it when it's accessed for the first time.
If __find_vmap_area() was part of the API, this loop could be left out
from __vmalloc_node_range() and the user of the allocation could
initialize the field, if needed.
What is the reason for keeping __find_vmap_area() private?
--
igor
