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)
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
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next prev parent reply other threads:[~2016-09-12 3:35 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-11 17:31 Dan Williams
2016-09-11 17:31 ` [RFC PATCH 2/2] x86: wire up mincore2() Dan Williams
2016-09-13 18:44 ` Ingo Molnar
2016-09-12 3:35 ` Nicholas Piggin [this message]
2016-09-12 17:29 ` [RFC PATCH 1/2] mm, mincore2(): retrieve dax and tlb-size attributes of an address range Dan Williams
2016-09-13 2:16 ` Nicholas Piggin
2016-09-13 3:49 ` Dan Williams
2016-09-12 6:29 ` Oliver O'Halloran
2016-09-12 17:25 ` Dan Williams
2016-09-12 10:09 ` Kirill A. Shutemov
2016-09-12 17:15 ` Dan Williams
2016-09-13 6:44 ` Christoph Hellwig
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