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[v6,07/39] mm: clarify __GFP_ZEROTAGS comment

Message ID cdffde013973c5634a447513e10ec0d21e8eee29.1643047180.git.andreyknvl@google.com (mailing list archive)
State New, archived
Headers show
Series kasan, vmalloc, arm64: add vmalloc tagging support for SW/HW_TAGS | expand

Commit Message

andrey.konovalov@linux.dev Jan. 24, 2022, 6:02 p.m. UTC 
From: Andrey Konovalov <andreyknvl@google.com>

__GFP_ZEROTAGS is intended as an optimization: if memory is zeroed during
allocation, it's possible to set memory tags at the same time with little
performance impact.

Clarify this intention of __GFP_ZEROTAGS in the comment.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>

---

Changes v4->v5:
- Mention optimization intention in the comment.
---
 include/linux/gfp.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)
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Patch

diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index 80f63c862be5..581a1f47b8a2 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -232,8 +232,10 @@  struct vm_area_struct;
  *
  * %__GFP_ZERO returns a zeroed page on success.
  *
- * %__GFP_ZEROTAGS returns a page with zeroed memory tags on success, if
- * __GFP_ZERO is set.
+ * %__GFP_ZEROTAGS zeroes memory tags at allocation time if the memory itself
+ * is being zeroed (either via __GFP_ZERO or via init_on_alloc). This flag is
+ * intended for optimization: setting memory tags at the same time as zeroing
+ * memory has minimal additional performace impact.
  *
  * %__GFP_SKIP_KASAN_POISON returns a page which does not need to be poisoned
  * on deallocation. Typically used for userspace pages. Currently only has an