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SubjectRe: [PATCH] fs/buffer.c: Add checking buffer head stat before clear
On Wed, 3 Feb 2021 14:14:50 +0800 Shaokun Zhang <zhangshaokun@hisilicon.com> wrote:

> From: Yang Guo <guoyang2@huawei.com>
>
> clear_buffer_new() is used to clear buffer new stat. When PAGE_SIZE
> is 64K, most buffer heads in the list are not needed to clear.
> clear_buffer_new() has an enpensive atomic modification operation,
> Let's add checking buffer head before clear it as __block_write_begin_int
> does which is good for performance.

Did this produce any measurable improvement?

Perhaps we should give clear_buffer_x() the same optimization as
set_buffer_x()?


static __always_inline void set_buffer_##name(struct buffer_head *bh) \
{ \
if (!test_bit(BH_##bit, &(bh)->b_state)) \
set_bit(BH_##bit, &(bh)->b_state); \
} \
static __always_inline void clear_buffer_##name(struct buffer_head *bh) \
{ \
clear_bit(BH_##bit, &(bh)->b_state); \
} \


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