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/mm/highmem.c b/mm/highmem.c
index 4212ad0..eb3b8c2 100644
--- 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);
}