diff mbox series

[v2,2/2] mm: Create non-atomic version of SetPageReserved for init use

Message ID 20180905211334.3286.84435.stgit@localhost.localdomain (mailing list archive)
State New, archived
Headers show
Series Address issues slowing memory init | expand

Commit Message

Alexander Duyck Sept. 5, 2018, 9:13 p.m. UTC 
From: Alexander Duyck <alexander.h.duyck@intel.com>

It doesn't make much sense to use the atomic SetPageReserved at init time
when we are using memset to clear the memory and manipulating the page
flags via simple "&=" and "|=" operations in __init_single_page.

This patch adds a non-atomic version __SetPageReserved that can be used
during page init and shows about a 10% improvement in initialization times
on the systems I have available for testing.

I tried adding a bit of documentation based on commit <f1dd2cd13c4> ("mm,
memory_hotplug: do not associate hotadded memory to zones until online").

Ideally the reserved flag should be set earlier since there is a brief
window where the page is initialization via __init_single_page and we have
not set the PG_Reserved flag. I'm leaving that for a future patch set as
that will require a more significant refactor.

Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
---
 include/linux/page-flags.h |    1 +
 mm/page_alloc.c            |   13 +++++++++++--
 2 files changed, 12 insertions(+), 2 deletions(-)

Comments

Michal Hocko Sept. 6, 2018, 5:49 a.m. UTC | #1 
On Wed 05-09-18 14:13:34, Alexander Duyck wrote:
[...]

just a nit

> @@ -1231,7 +1231,8 @@ void __meminit reserve_bootmem_region(phys_addr_t start, phys_addr_t end)
>  			/* Avoid false-positive PageTail() */
>  			INIT_LIST_HEAD(&page->lru);
>  
> -			SetPageReserved(page);
> +			/* no need for atomic set_bit at init time */
> +			__SetPageReserved(page);

OK but I guess it would be much more clear to say
			/*
			 * no need for atomic set_bit because the struct
			 * page is not visible yet so nobody should
			 * access it yet.
			 */
>  		}
>  	}
>  }
diff mbox series

Patch

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 0e95ca63375a..daee3ea2d1ed 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -300,6 +300,7 @@  static inline void page_init_poison(struct page *page, size_t size)
 
 PAGEFLAG(Reserved, reserved, PF_NO_COMPOUND)
 	__CLEARPAGEFLAG(Reserved, reserved, PF_NO_COMPOUND)
+	__SETPAGEFLAG(Reserved, reserved, PF_NO_COMPOUND)
 PAGEFLAG(SwapBacked, swapbacked, PF_NO_TAIL)
 	__CLEARPAGEFLAG(SwapBacked, swapbacked, PF_NO_TAIL)
 	__SETPAGEFLAG(SwapBacked, swapbacked, PF_NO_TAIL)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 05e983f42316..f2602021032f 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1231,7 +1231,8 @@  void __meminit reserve_bootmem_region(phys_addr_t start, phys_addr_t end)
 			/* Avoid false-positive PageTail() */
 			INIT_LIST_HEAD(&page->lru);
 
-			SetPageReserved(page);
+			/* no need for atomic set_bit at init time */
+			__SetPageReserved(page);
 		}
 	}
 }
@@ -5517,8 +5518,16 @@  void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
 not_early:
 		page = pfn_to_page(pfn);
 		__init_single_page(page, pfn, zone, nid);
+
+		/*
+		 * Mark page reserved as it will need to wait for onlining
+		 * phase for it to be fully associated with a zone.
+		 *
+		 * We can use the non-atomic __set_bit operation for setting
+		 * the flag as we are still initializing the pages.
+		 */
 		if (context == MEMMAP_HOTPLUG)
-			SetPageReserved(page);
+			__SetPageReserved(page);
 
 		/*
 		 * Mark the block movable so that blocks are reserved for