linux-kernel - Re: [PATCH 1/2] mm, thp: introduce dedicated transparent huge page allocation interfaces

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Message-ID: <20171019124931.p5zdvs2kdwu73mwh@dhcp22.suse.cz>
Date:   Thu, 19 Oct 2017 14:49:31 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     "Du, Changbin" <changbin.du@...el.com>
Cc:     akpm@...ux-foundation.org, corbet@....net, hughd@...gle.com,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [PATCH 1/2] mm, thp: introduce dedicated transparent huge page
 allocation interfaces

On Wed 18-10-17 19:00:26, Du, Changbin wrote:
> Hi Hocko,
> 
> On Tue, Oct 17, 2017 at 12:20:52PM +0200, Michal Hocko wrote:
> > [CC Kirill]
> > 
> > On Mon 16-10-17 17:19:16, changbin.du@...el.com wrote:
> > > From: Changbin Du <changbin.du@...el.com>
> > > 
> > > This patch introduced 4 new interfaces to allocate a prepared
> > > transparent huge page.
> > >   - alloc_transhuge_page_vma
> > >   - alloc_transhuge_page_nodemask
> > >   - alloc_transhuge_page_node
> > >   - alloc_transhuge_page
> > > 
> > > The aim is to remove duplicated code and simplify transparent
> > > huge page allocation. These are similar to alloc_hugepage_xxx
> > > which are for hugetlbfs pages. This patch does below changes:
> > >   - define alloc_transhuge_page_xxx interfaces
> > >   - apply them to all existing code
> > >   - declare prep_transhuge_page as static since no others use it
> > >   - remove alloc_hugepage_vma definition since it no longer has users
> > 
> > So what exactly is the advantage of the new API? The diffstat doesn't
> > sound very convincing to me.
> >
> The caller only need one step to allocate thp. Several LOCs removed for all the
> caller side with this change. So it's little more convinent.

Yeah, but the overall result is more code. So I am not really convinced. 
-- 
Michal Hocko
SUSE Labs