mm/highmem: remove deprecated kmap_atomic

kmap_atomic() is being deprecated in favor of kmap_local_page().

Replace the uses of kmap_atomic() within the highmem code.

On profiling clear_huge_page() using ftrace an improvement of 62% was
observed on the below setup.

Setup:-
Below data has been collected on Qualcomm's SM7250 SoC THP enabled
(kernel v4.19.113) with only CPU-0(Cortex-A55) and CPU-7(Cortex-A76)
switched on and set to max frequency, also DDR set to perf governor.

FTRACE Data:-

Base data:-
Number of iterations: 48
Mean of allocation time: 349.5 us
std deviation: 74.5 us

v4 data:-
Number of iterations: 48
Mean of allocation time: 131 us
std deviation: 32.7 us

The following simple userspace experiment to allocate
100MB(BUF_SZ) of pages and writing to it gave us a good insight,
we observed an improvement of 42% in allocation and writing timings.
-------------------------------------------------------------
Test code snippet
-------------------------------------------------------------
      clock_start();
      buf = malloc(BUF_SZ); /* Allocate 100 MB of memory */

        for(i=0; i < BUF_SZ_PAGES; i++)
        {
                *((int *)(buf + (i*PAGE_SIZE))) = 1;
        }
      clock_end();
-------------------------------------------------------------

Malloc test timings for 100MB anon allocation:-

Base data:-
Number of iterations: 100
Mean of allocation time: 31831 us
std deviation: 4286 us

v4 data:-
Number of iterations: 100
Mean of allocation time: 18193 us
std deviation: 4915 us

[willy@infradead.org: fix zero_user_segments()]
Link: https://lkml.kernel.org/r/YYVhHCJcm2DM2G9u@casper.infradead.org
Link: https://lkml.kernel.org/r/20210204073255.20769-2-prathu.baronia@oneplus.com
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Prathu Baronia <prathu.baronia@oneplus.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index b4c49f9cc379eee1f0cb98ad3e5151ad0a08d4ab..31ebee36f26ce00f17b5e888fa619021e2a5541f 100644 (file)
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -143,9 +143,9 @@ static inline void invalidate_kernel_vmap_range(void *vaddr, int size)
 #ifndef clear_user_highpage
 static inline void clear_user_highpage(struct page *page, unsigned long vaddr)
 {
-       void *addr = kmap_atomic(page);
+       void *addr = kmap_local_page(page);
        clear_user_page(addr, vaddr, page);
-       kunmap_atomic(addr);
+       kunmap_local(addr);
 }
 #endif
 
@@ -177,9 +177,9 @@ alloc_zeroed_user_highpage_movable(struct vm_area_struct *vma,
 
 static inline void clear_highpage(struct page *page)
 {
-       void *kaddr = kmap_atomic(page);
+       void *kaddr = kmap_local_page(page);
        clear_page(kaddr);
-       kunmap_atomic(kaddr);
+       kunmap_local(kaddr);
 }
 
 #ifndef __HAVE_ARCH_TAG_CLEAR_HIGHPAGE
@@ -202,7 +202,7 @@ static inline void zero_user_segments(struct page *page,
                unsigned start1, unsigned end1,
                unsigned start2, unsigned end2)
 {
-       void *kaddr = kmap_atomic(page);
+       void *kaddr = kmap_local_page(page);
        unsigned int i;
 
        BUG_ON(end1 > page_size(page) || end2 > page_size(page));
@@ -213,7 +213,7 @@ static inline void zero_user_segments(struct page *page,
        if (end2 > start2)
                memset(kaddr + start2, 0, end2 - start2);
 
-       kunmap_atomic(kaddr);
+       kunmap_local(kaddr);
        for (i = 0; i < compound_nr(page); i++)
                flush_dcache_page(page + i);
 }
@@ -238,11 +238,11 @@ static inline void copy_user_highpage(struct page *to, struct page *from,
 {
        char *vfrom, *vto;
 
-       vfrom = kmap_atomic(from);
-       vto = kmap_atomic(to);
+       vfrom = kmap_local_page(from);
+       vto = kmap_local_page(to);
        copy_user_page(vto, vfrom, vaddr, to);
-       kunmap_atomic(vto);
-       kunmap_atomic(vfrom);
+       kunmap_local(vto);
+       kunmap_local(vfrom);
 }
 
 #endif
@@ -253,11 +253,11 @@ static inline void copy_highpage(struct page *to, struct page *from)
 {
        char *vfrom, *vto;
 
-       vfrom = kmap_atomic(from);
-       vto = kmap_atomic(to);
+       vfrom = kmap_local_page(from);
+       vto = kmap_local_page(to);
        copy_page(vto, vfrom);
-       kunmap_atomic(vto);
-       kunmap_atomic(vfrom);
+       kunmap_local(vto);
+       kunmap_local(vfrom);
 }
 
 #endif

diff --git a/mm/highmem.c b/mm/highmem.c
index 4212ad0e4a195f7ee16ecd9216b92c68fa855315..eb3b8c288de441b6c1bcdbb1b4a34162d43bd114 100644 (file)
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -383,7 +383,7 @@ void zero_user_segments(struct page *page, unsigned start1, unsigned end1,
                        unsigned this_end = min_t(unsigned, end1, PAGE_SIZE);
 
                        if (end1 > start1) {
-                               kaddr = kmap_atomic(page + i);
+                               kaddr = kmap_local_page(page + i);
                                memset(kaddr + start1, 0, this_end - start1);
                        }
                        end1 -= this_end;
@@ -398,7 +398,7 @@ void zero_user_segments(struct page *page, unsigned start1, unsigned end1,
 
                        if (end2 > start2) {
                                if (!kaddr)
-                                       kaddr = kmap_atomic(page + i);
+                                       kaddr = kmap_local_page(page + i);
                                memset(kaddr + start2, 0, this_end - start2);
                        }
                        end2 -= this_end;
@@ -406,7 +406,7 @@ void zero_user_segments(struct page *page, unsigned start1, unsigned end1,
                }
 
                if (kaddr) {
-                       kunmap_atomic(kaddr);
+                       kunmap_local(kaddr);
                        flush_dcache_page(page + i);
                }