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Subject: Re: [RFC PATCH 3/3] mm, proc: report PR_SET_THP_DISABLE in proc
From:   William Kucharski <william.kucharski@oracle.com>
In-Reply-To: <20181127131707.GW12455@dhcp22.suse.cz>
Date:   Tue, 27 Nov 2018 07:50:08 -0700
Cc:     linux-api@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Alexey Dobriyan <adobriyan@gmail.com>, linux-mm@kvack.org,
        LKML <linux-kernel@vger.kernel.org>
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Message-Id: <04647F77-FE93-4A8E-90C1-4245709B88A5@oracle.com>
References: <20181120103515.25280-1-mhocko@kernel.org>
 <20181120103515.25280-4-mhocko@kernel.org>
 <0ACDD94B-75AD-4DD0-B2E3-32C0EDFBAA5E@oracle.com>
 <20181127131707.GW12455@dhcp22.suse.cz>
To:     Michal Hocko <mhocko@kernel.org>
Sender: linux-kernel-owner@vger.kernel.org
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> On Nov 27, 2018, at 6:17 AM, Michal Hocko <mhocko@kernel.org> wrote:
> 
> This is only about the process wide flag to disable THP. I do not see
> how this can be alighnement related. I suspect you wanted to ask in the
> smaps patch?

No, answered below.

> 
>> I'm having to deal with both these issues in the text page THP
>> prototype I've been working on for some time now.
> 
> Could you be more specific about the issue and how the alignment comes
> into the game? The only thing I can think of is to not report VMAs
> smaller than the THP as eligible. Is this what you are looking for?

Basically, if the faulting VA is one that cannot be mapped with a THP
due to alignment or size constraints, it may be "eligible" for THP
mapping but ultimately can't be.

I was just double checking that this was meant to be more of a check done
before code elsewhere performs additional checks and does the actual THP
mapping, not an all-encompassing go/no go check for THP mapping.

    Thanks,
         William Kucharski