From: Nicholas Piggin <npiggin-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
To: Dan Williams <dan.j.williams-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Cc: Andrea Arcangeli
<aarcange-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
linux-arch-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
Xiao Guangrong
<guangrong.xiao-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>,
Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>,
linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org,
linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
Dave Hansen <dave.hansen-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org,
Andrew Morton
<akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
"Kirill A. Shutemov"
<kirill.shutemov-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
Subject: Re: [RFC PATCH 1/2] mm, mincore2(): retrieve dax and tlb-size attributes of an address range
Date: Mon, 12 Sep 2016 13:35:36 +1000 [thread overview]
Message-ID: <20160912133536.1bdb57a9@roar.ozlabs.ibm.com> (raw)
In-Reply-To: <147361509579.17004.5258725187329709824.stgit-p8uTFz9XbKj2zm6wflaqv1nYeNYlB/vhral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
On Sun, 11 Sep 2016 10:31:35 -0700
Dan Williams <dan.j.williams-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org> wrote:
> As evidenced by this bug report [1], userspace libraries are interested
> in whether a mapping is DAX mapped, i.e. no intervening page cache.
> Rather than using the ambiguous VM_MIXEDMAP flag in smaps, provide an
> explicit "is dax" indication as a new flag in the page vector populated
> by mincore.
Can you cc linux-arch when adding new syscalls (or other such things that
need arch enablement).
I wonder if the changelog for a new syscall should have a bit more grandeur.
Without seeing patch 2, you might not know this was a new syscall just by
reading the subject and changelog.
mincore() defines other bits to be reserved, but I guess it probably breaks
things if you suddenly started using them.
It's a bit sad to introduce a new syscall for this and immediately use up
all bits that can be returned. Would it be a serious problem to return a
larger mask per page?
Thanks,
Nick
WARNING: multiple messages have this Message-ID (diff)
From: Nicholas Piggin <npiggin@gmail.com>
To: Dan Williams <dan.j.williams@intel.com>
Cc: linux-mm@kvack.org, Andrea Arcangeli <aarcange@redhat.com>,
Xiao Guangrong <guangrong.xiao@linux.intel.com>,
Arnd Bergmann <arnd@arndb.de>,
linux-nvdimm@lists.01.org, linux-api@vger.kernel.org,
Dave Hansen <dave.hansen@linux.intel.com>,
linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
linux-arch@vger.kernel.org
Subject: Re: [RFC PATCH 1/2] mm, mincore2(): retrieve dax and tlb-size attributes of an address range
Date: Mon, 12 Sep 2016 13:35:36 +1000 [thread overview]
Message-ID: <20160912133536.1bdb57a9@roar.ozlabs.ibm.com> (raw)
Message-ID: <20160912033536.6e2cQTRViylX5fxwQ6bi8-laKsIlNaZIffKjASD9CzA@z> (raw)
In-Reply-To: <147361509579.17004.5258725187329709824.stgit@dwillia2-desk3.amr.corp.intel.com>
On Sun, 11 Sep 2016 10:31:35 -0700
Dan Williams <dan.j.williams@intel.com> wrote:
> As evidenced by this bug report [1], userspace libraries are interested
> in whether a mapping is DAX mapped, i.e. no intervening page cache.
> Rather than using the ambiguous VM_MIXEDMAP flag in smaps, provide an
> explicit "is dax" indication as a new flag in the page vector populated
> by mincore.
Can you cc linux-arch when adding new syscalls (or other such things that
need arch enablement).
I wonder if the changelog for a new syscall should have a bit more grandeur.
Without seeing patch 2, you might not know this was a new syscall just by
reading the subject and changelog.
mincore() defines other bits to be reserved, but I guess it probably breaks
things if you suddenly started using them.
It's a bit sad to introduce a new syscall for this and immediately use up
all bits that can be returned. Would it be a serious problem to return a
larger mask per page?
Thanks,
Nick
next parent reply other threads:[~2016-09-12 3:35 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <147361509579.17004.5258725187329709824.stgit@dwillia2-desk3.amr.corp.intel.com>
[not found] ` <147361509579.17004.5258725187329709824.stgit-p8uTFz9XbKj2zm6wflaqv1nYeNYlB/vhral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2016-09-12 3:35 ` Nicholas Piggin [this message]
2016-09-12 3:35 ` [RFC PATCH 1/2] mm, mincore2(): retrieve dax and tlb-size attributes of an address range Nicholas Piggin
2016-09-12 17:29 ` Dan Williams
2016-09-12 17:29 ` Dan Williams
[not found] ` <CAPcyv4hS7i1DApKPDB5PkfBNZVbk321FgP94kUDjmuyGXDidZg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2016-09-13 2:16 ` Nicholas Piggin
2016-09-13 2:16 ` Nicholas Piggin
[not found] ` <20160913121645.652e6512-a5aMA/AkCkgK5Ils6ZIQy0EOCMrvLtNR@public.gmane.org>
2016-09-13 3:49 ` Dan Williams
2016-09-13 3:49 ` Dan Williams
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