From: John Hubbard <jhubbard@nvidia.com>
To: Ira Weiny <ira.weiny@intel.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>, <linux-rdma@vger.kernel.org>,
<linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Davidlohr Bueso <dave@stgolabs.net>, <netdev@vger.kernel.org>,
Mike Marciniszyn <mike.marciniszyn@intel.com>,
Dennis Dalessandro <dennis.dalessandro@intel.com>,
Doug Ledford <dledford@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Dan Williams <dan.j.williams@intel.com>
Subject: Re: [PATCH 2/3] mm/gup: Introduce get_user_pages_fast_longterm()
Date: Mon, 11 Feb 2019 13:39:12 -0800 [thread overview]
Message-ID: <fc9c880b-24f8-7063-6094-00175bc27f7d@nvidia.com> (raw)
In-Reply-To: <20190211212652.GA7790@iweiny-DESK2.sc.intel.com>
On 2/11/19 1:26 PM, Ira Weiny wrote:
> On Mon, Feb 11, 2019 at 01:13:56PM -0800, John Hubbard wrote:
>> On 2/11/19 12:39 PM, Jason Gunthorpe wrote:
>>> On Mon, Feb 11, 2019 at 12:16:42PM -0800, ira.weiny@intel.com wrote:
>>>> From: Ira Weiny <ira.weiny@intel.com>
>> [...]
>> It seems to me that the longterm vs. short-term is of questionable value.
>
> This is exactly why I did not post this before. I've been waiting our other
> discussions on how GUP pins are going to be handled to play out. But with the
> netdev thread today[1] it seems like we need to make sure we have a "safe" fast
> variant for a while. Introducing FOLL_LONGTERM seemed like the cleanest way to
> do that even if we will not need the distinction in the future... :-(
Yes, I agree. Below...
> [...]
> This is also why I did not change the get_user_pages_longterm because we could
> be ripping this all out by the end of the year... (I hope. :-)
>
> So while this does "pollute" the GUP family of calls I'm hoping it is not
> forever.
>
> Ira
>
> [1] https://lkml.org/lkml/2019/2/11/1789
>
Yes, and to be clear, I think your patchset here is fine. It is easy to find
the FOLL_LONGTERM callers if and when we want to change anything. I just think
also it's appopriate to go a bit further, and use FOLL_LONGTERM all by itself.
That's because in either design outcome, it's better that way:
-- If we keep the concept of "I'm a long-term gup call site", then FOLL_LONGTERM
is just right. The gup API already has _fast and non-fast variants, and once
you get past a couple, you end up with a multiplication of names that really
work better as flags. We're there.
-- If we drop the concept, then you've already done part of the work, by removing
the _longterm API variants.
thanks,
--
John Hubbard
NVIDIA
next prev parent reply other threads:[~2019-02-11 21:39 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-11 20:16 [PATCH 0/3] Add gup fast + longterm and use it in HFI1 ira.weiny
2019-02-11 20:16 ` [PATCH 1/3] mm/gup: Change "write" parameter to flags ira.weiny
2019-02-11 20:16 ` [PATCH 2/3] mm/gup: Introduce get_user_pages_fast_longterm() ira.weiny
2019-02-11 20:39 ` Jason Gunthorpe
2019-02-11 21:13 ` John Hubbard
2019-02-11 21:26 ` Ira Weiny
2019-02-11 21:39 ` John Hubbard [this message]
2019-02-11 21:45 ` Dan Williams
2019-02-11 21:52 ` Ira Weiny
2019-02-11 22:01 ` John Hubbard
2019-02-11 22:06 ` Jason Gunthorpe
2019-02-11 22:55 ` Dan Williams
2019-02-11 23:04 ` Weiny, Ira
2019-02-11 23:25 ` Jason Gunthorpe
2019-02-12 0:08 ` Ira Weiny
2019-02-11 20:16 ` [PATCH 3/3] IB/HFI1: Use new get_user_pages_fast_longterm() ira.weiny
2019-02-11 20:34 ` [PATCH 0/3] Add gup fast + longterm and use it in HFI1 Davidlohr Bueso
2019-02-11 20:47 ` Jason Gunthorpe
2019-02-11 21:42 ` Ira Weiny
2019-02-11 22:22 ` Jason Gunthorpe
2019-02-11 22:40 ` Weiny, Ira
2019-02-11 22:50 ` Jason Gunthorpe
2019-02-11 21:29 ` Ira Weiny
2019-02-11 20:40 ` Jason Gunthorpe
2019-02-11 21:14 ` Weiny, Ira
2019-02-11 22:23 ` Jason Gunthorpe
2019-02-13 23:04 ` [PATCH V2 0/7] Add FOLL_LONGTERM to GUP fast and use it ira.weiny
2019-02-13 23:04 ` [PATCH V2 1/7] mm/gup: Replace get_user_pages_longterm() with FOLL_LONGTERM ira.weiny
2019-02-13 23:04 ` [PATCH V2 2/7] mm/gup: Change write parameter to flags in fast walk ira.weiny
2019-02-13 23:04 ` [PATCH V2 3/7] mm/gup: Change GUP fast to use flags rather than a write 'bool' ira.weiny
2019-02-13 23:04 ` [PATCH V2 4/7] mm/gup: Add FOLL_LONGTERM capability to GUP fast ira.weiny
2019-02-13 23:04 ` [PATCH V2 5/7] IB/hfi1: Use the new FOLL_LONGTERM flag to get_user_pages_fast() ira.weiny
2019-02-13 23:04 ` [PATCH V2 6/7] IB/qib: " ira.weiny
2019-02-13 23:04 ` [PATCH V2 7/7] IB/mthca: " ira.weiny
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