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From: Anshuman Khandual <khandual@linux.vnet.ibm.com>
To: Michal Hocko <mhocko@kernel.org>,
	Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	akpm@linux-foundation.org, shli@kernel.org
Subject: Re: [PATCH] mm/swap: Use page flags to determine LRU list in __activate_page()
Date: Mon, 23 Oct 2017 08:52:34 +0530	[thread overview]
Message-ID: <d01827c0-8858-5688-dc16-1e2f597ec55c@linux.vnet.ibm.com> (raw)
In-Reply-To: <20171019153322.c4uqalws7l7fdzcx@dhcp22.suse.cz>

On 10/19/2017 09:03 PM, Michal Hocko wrote:
> On Thu 19-10-17 20:26:57, Anshuman Khandual wrote:
>> Its already assumed that the PageActive flag is clear on the input
>> page, hence page_lru(page) will pick the base LRU for the page. In
>> the same way page_lru(page) will pick active base LRU, once the
>> flag PageActive is set on the page. This change of LRU list should
>> happen implicitly through the page flags instead of being hard
>> coded.
> 
> The patch description tells what but it doesn't explain _why_? Does the
> resulting code is better, more optimized or is this a pure readability
> thing?

Not really. Not only it removes couple of lines of code but it also
makes it look more logical from function flow point of view as well.

> 
> All I can see is that page_lru is more complex and a large part of it
> can be optimized away which has been done manually here. I suspect the
> compiler can deduce the same thing.

Why not ? I mean, that is the essence of the function page_lru() which
should get us the exact LRU list the page should be on and hence we
should not hand craft these manually.

WARNING: multiple messages have this Message-ID (diff)
From: Anshuman Khandual <khandual@linux.vnet.ibm.com>
To: Michal Hocko <mhocko@kernel.org>,
	Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	akpm@linux-foundation.org, shli@kernel.org
Subject: Re: [PATCH] mm/swap: Use page flags to determine LRU list in __activate_page()
Date: Mon, 23 Oct 2017 08:52:34 +0530	[thread overview]
Message-ID: <d01827c0-8858-5688-dc16-1e2f597ec55c@linux.vnet.ibm.com> (raw)
In-Reply-To: <20171019153322.c4uqalws7l7fdzcx@dhcp22.suse.cz>

On 10/19/2017 09:03 PM, Michal Hocko wrote:
> On Thu 19-10-17 20:26:57, Anshuman Khandual wrote:
>> Its already assumed that the PageActive flag is clear on the input
>> page, hence page_lru(page) will pick the base LRU for the page. In
>> the same way page_lru(page) will pick active base LRU, once the
>> flag PageActive is set on the page. This change of LRU list should
>> happen implicitly through the page flags instead of being hard
>> coded.
> 
> The patch description tells what but it doesn't explain _why_? Does the
> resulting code is better, more optimized or is this a pure readability
> thing?

Not really. Not only it removes couple of lines of code but it also
makes it look more logical from function flow point of view as well.

> 
> All I can see is that page_lru is more complex and a large part of it
> can be optimized away which has been done manually here. I suspect the
> compiler can deduce the same thing.

Why not ? I mean, that is the essence of the function page_lru() which
should get us the exact LRU list the page should be on and hence we
should not hand craft these manually.

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  reply	other threads:[~2017-10-23  3:22 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-10-19 14:56 [PATCH] mm/swap: Use page flags to determine LRU list in __activate_page() Anshuman Khandual
2017-10-19 14:56 ` Anshuman Khandual
2017-10-19 15:33 ` Michal Hocko
2017-10-19 15:33   ` Michal Hocko
2017-10-23  3:22   ` Anshuman Khandual [this message]
2017-10-23  3:22     ` Anshuman Khandual
2017-10-27  4:06     ` Anshuman Khandual
2017-10-27  4:06       ` Anshuman Khandual
2017-10-27  7:57       ` Michal Hocko
2017-10-27  7:57         ` Michal Hocko
2017-10-31 12:45   ` Vlastimil Babka
2017-10-31 12:45     ` Vlastimil Babka
2017-11-02 11:44     ` Anshuman Khandual
2017-11-02 11:44       ` Anshuman Khandual

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