linux-kernel - [PATCH] percpu: remove the unnecessary operation for bitmaps in finding suitable region

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Date:   Sat, 14 Aug 2021 20:20:18 -0700
From:   Junhua Huang <junhuahuangdream@....com>
To:     dennis@...nel.org, tj@...nel.org, cl@...ux.com
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Junhua Huang <huang.junhua@....com.cn>
Subject: [PATCH] percpu: remove the unnecessary operation for bitmaps in finding suitable region

From: Junhua Huang <huang.junhua@....com.cn>

We use pcpu_next_fit_region to find the next fit region for alloc. Once
return, the region fit the request and then break the loop, or get the
next start offset from pcpu_is_populated. So there is no necessary to
add bits to bit_off. At the same time, bits will set 0 in 
pcpu_next_fit_region each time, so I think it is unnecessary to 
set bits zero in pcpu_for_each_fit_region loops.

Signed-off-by: Junhua Huang <huang.junhua@....com.cn>
---
 mm/percpu.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/mm/percpu.c b/mm/percpu.c
index 7f2e0151c4e2..ec7a5d10f6c9 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -489,7 +489,6 @@ static void pcpu_next_fit_region(struct pcpu_chunk *chunk, int alloc_bits,
 	for (pcpu_next_fit_region((chunk), (alloc_bits), (align), &(bit_off), \
 				  &(bits));				      \
 	     (bit_off) < pcpu_chunk_map_bits((chunk));			      \
-	     (bit_off) += (bits),					      \
 	     pcpu_next_fit_region((chunk), (alloc_bits), (align), &(bit_off), \
 				  &(bits)))
 
@@ -1126,7 +1125,6 @@ static int pcpu_find_block_fit(struct pcpu_chunk *chunk, int alloc_bits,
 			break;
 
 		bit_off = next_off;
-		bits = 0;
 	}
 
 	if (bit_off == pcpu_chunk_map_bits(chunk))
-- 
2.25.1