sparc64: optimize struct page zeroing

Add an optimized mm_zero_struct_page(), so struct page's are zeroed
without calling memset().  We do eight to ten regular stores based on
the size of struct page.  Compiler optimizes out the conditions of
switch() statement.

SPARC-M6 with 15T of memory, single thread performance:

                               BASE            FIX  OPTIMIZED_FIX
        bootmem_init   28.440467985s   2.305674818s   2.305161615s
free_area_init_nodes  202.845901673s 225.343084508s 172.556506560s
                      --------------------------------------------
Total                 231.286369658s 227.648759326s 174.861668175s

BASE:  current linux
FIX:   This patch series without "optimized struct page zeroing"
OPTIMIZED_FIX: This patch series including the current patch.

bootmem_init() is where memory for struct pages is zeroed during
allocation.  Note, about two seconds in this function is a fixed time:
it does not increase as memory is increased.

Link: http://lkml.kernel.org/r/20171013173214.27300-11-pasha.tatashin@oracle.com
Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
Reviewed-by: Steven Sistare <steven.sistare@oracle.com>
Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Reviewed-by: Bob Picco <bob.picco@oracle.com>
Acked-by: David S. Miller <davem@davemloft.net>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/sparc/include/asm/pgtable_64.h b/arch/sparc/include/asm/pgtable_64.h
index fd9d9ba..5a9e96b 100644 (file)
--- a/arch/sparc/include/asm/pgtable_64.h
+++ b/arch/sparc/include/asm/pgtable_64.h
@@ -231,6 +231,36 @@ extern unsigned long _PAGE_ALL_SZ_BITS;
 extern struct page *mem_map_zero;
 #define ZERO_PAGE(vaddr)       (mem_map_zero)
 
+/* This macro must be updated when the size of struct page grows above 80
+ * or reduces below 64.
+ * The idea that compiler optimizes out switch() statement, and only
+ * leaves clrx instructions
+ */
+#define        mm_zero_struct_page(pp) do {                                    \
+       unsigned long *_pp = (void *)(pp);                              \
+                                                                       \
+        /* Check that struct page is either 64, 72, or 80 bytes */     \
+       BUILD_BUG_ON(sizeof(struct page) & 7);                          \
+       BUILD_BUG_ON(sizeof(struct page) < 64);                         \
+       BUILD_BUG_ON(sizeof(struct page) > 80);                         \
+                                                                       \
+       switch (sizeof(struct page)) {                                  \
+       case 80:                                                        \
+               _pp[9] = 0;     /* fallthrough */                       \
+       case 72:                                                        \
+               _pp[8] = 0;     /* fallthrough */                       \
+       default:                                                        \
+               _pp[7] = 0;                                             \
+               _pp[6] = 0;                                             \
+               _pp[5] = 0;                                             \
+               _pp[4] = 0;                                             \
+               _pp[3] = 0;                                             \
+               _pp[2] = 0;                                             \
+               _pp[1] = 0;                                             \
+               _pp[0] = 0;                                             \
+       }                                                               \
+} while (0)
+
 /* PFNs are real physical page numbers.  However, mem_map only begins to record
  * per-page information starting at pfn_base.  This is to handle systems where
  * the first physical page in the machine is at some huge physical address,