linux-kernel - Re: [PATCH] mm,hugetlb: compute page_size

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Date:   Thu, 30 Mar 2017 08:12:45 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Andi Kleen <ak@...ux.intel.com>
Cc:     Matthew Wilcox <willy@...radead.org>, akpm@...ux-foundation.org,
        mtk.manpages@...il.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Davidlohr Bueso <dbueso@...e.de>,
        khandual@...ux.vnet.ibm.com
Subject: Re: [PATCH] mm,hugetlb: compute page_size_log properly

On Wed 29-03-17 10:45:14, Andi Kleen wrote:
> On Wed, Mar 29, 2017 at 10:06:25AM +0200, Michal Hocko wrote:
> > On Tue 28-03-17 10:54:08, Matthew Wilcox wrote:
> > > On Tue, Mar 28, 2017 at 09:55:13AM -0700, Davidlohr Bueso wrote:
> > > > Do we have any consensus here? Keeping SHM_HUGE_* is currently
> > > > winning 2-1. If there are in fact users out there computing the
> > > > value manually, then I am ok with keeping it and properly exporting
> > > > it. Michal?
> > > 
> > > Well, let's see what it looks like to do that.  I went down the rabbit
> > > hole trying to understand why some of the SHM_ flags had the same value
> > > as each other until I realised some of them were internal flags, some
> > > were flags to shmat() and others were flags to shmget().  Hopefully I
> > > disambiguated them nicely in this patch.  I also added 8MB and 16GB sizes.
> > > Any more architectures with a pet favourite huge/giant page size we
> > > should add convenience defines for?
> > 
> > Do we actually have any users?
> 
> Yes this feature is widely used.

Considering that none of SHM_HUGE* has been exported to the userspace
headers all the users would have to use the this flag by the value and I
am quite skeptical that application actually do that. Could you point me
to some projects that use this?
-- 
Michal Hocko
SUSE Labs