linux-kernel - Re: [patch] mm, thp: always direct reclaim for MADV

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Message-ID: <alpine.DEB.2.10.1612281332320.13632@chino.kir.corp.google.com>
Date:   Wed, 28 Dec 2016 13:33:49 -0800 (PST)
From:   David Rientjes <rientjes@...gle.com>
To:     Michal Hocko <mhocko@...nel.org>
cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Jonathan Corbet <corbet@....net>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Mel Gorman <mgorman@...hsingularity.net>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [patch] mm, thp: always direct reclaim for MADV_HUGEPAGE even
 when deferred

On Wed, 28 Dec 2016, Michal Hocko wrote:

> I do care more about _users_ and their _experience_ than what
> application _writers_ think is the best. This is the whole point
> of giving the defrag tunable. madvise(MADV_HUGEPAGE) is just a hint to
> the system that using transparent hugepages is _preferable_, not
> mandatory. We have an option to allow stalls for those vmas to increase
> the allocation success rate. We also have tunable to completely ignore
> it. And we should also have an option to not stall.
> 

The application developer who uses madvise(MADV_HUGEPAGE) is doing so for 
a reason.

We lack the ability to defragment in the background for all users who 
don't want to block while allowing madvise(MADV_HUGEPAGE) users to block, 
as the changelog for this patch clearly indicates.

Thanks.