From: Michal Hocko <mhocko@kernel.org>
To: 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: Fri, 27 Oct 2017 09:57:27 +0200 [thread overview]
Message-ID: <20171027075727.pc7mj4giv3anewbi@dhcp22.suse.cz> (raw)
In-Reply-To: <2fc28494-d0d2-9b65-aeb7-1ccabf210917@linux.vnet.ibm.com>
On Fri 27-10-17 09:36:37, Anshuman Khandual wrote:
> On 10/23/2017 08:52 AM, Anshuman Khandual wrote:
> > 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.
>
> Hi Michal,
>
> Did not hear from you on this. So wondering what is the verdict
> about this patch ?
IMHO, there is no reason to change the code as it doesn't solve any real
problem or it doesn't make the code more effective AFAICS.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2017-10-27 7:57 UTC|newest]
Thread overview: 7+ 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 15:33 ` Michal Hocko
2017-10-23 3:22 ` Anshuman Khandual
2017-10-27 4:06 ` Anshuman Khandual
2017-10-27 7:57 ` Michal Hocko [this message]
2017-10-31 12:45 ` Vlastimil Babka
2017-11-02 11:44 ` Anshuman Khandual
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