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From: Matthew Wilcox <willy@infradead.org>
To: Shaokun Zhang <zhangshaokun@hisilicon.com>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	Yuqi Jin <jinyuqi@huawei.com>, Will Deacon <will@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>
Subject: Re: [PATCH] fs: Optimized fget to improve performance
Date: Thu, 27 Aug 2020 13:30:40 +0100	[thread overview]
Message-ID: <20200827123040.GE14765@casper.infradead.org> (raw)
In-Reply-To: <1598523584-25601-1-git-send-email-zhangshaokun@hisilicon.com>

On Thu, Aug 27, 2020 at 06:19:44PM +0800, Shaokun Zhang wrote:
> From: Yuqi Jin <jinyuqi@huawei.com>
> 
> It is well known that the performance of atomic_add is better than that of
> atomic_cmpxchg.

I don't think that's well-known at all.

> +static inline bool get_file_unless_negative(atomic_long_t *v, long a)
> +{
> +	long c = atomic_long_read(v);
> +
> +	if (c <= 0)
> +		return 0;
> +
> +	return atomic_long_add_return(a, v) - 1;
> +}
> +
>  #define get_file_rcu_many(x, cnt)	\
> -	atomic_long_add_unless(&(x)->f_count, (cnt), 0)
> +	get_file_unless_negative(&(x)->f_count, (cnt))
>  #define get_file_rcu(x) get_file_rcu_many((x), 1)
>  #define file_count(x)	atomic_long_read(&(x)->f_count)

I think you should be proposing a patch to fix atomic_long_add_unless()
on arm64 instead.

  reply	other threads:[~2020-08-27 12:33 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-27 10:19 Shaokun Zhang
2020-08-27 12:30 ` Matthew Wilcox [this message]
2020-08-27 13:07   ` David Laight
2020-08-27 14:28 ` [NAK] " Al Viro
2020-08-28 11:04   ` Will Deacon
2020-08-31  1:43   ` Shaokun Zhang
2020-08-31  3:21     ` Al Viro
2020-09-01  9:29       ` David Laight

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