From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: [PATCH 3/4] infiniband/mm: convert to the new put_user_page() call To: Dennis Dalessandro , Jason Gunthorpe , CC: Matthew Wilcox , Michal Hocko , Christopher Lameter , Dan Williams , Jan Kara , Al Viro , , LKML , linux-rdma , , Doug Ledford , Mike Marciniszyn , Christian Benvenuti References: <20180928053949.5381-1-jhubbard@nvidia.com> <20180928053949.5381-3-jhubbard@nvidia.com> <20180928153922.GA17076@ziepe.ca> <36bc65a3-8c2a-87df-44fc-89a1891b86db@nvidia.com> From: John Hubbard Message-ID: Date: Tue, 2 Oct 2018 22:40:43 -0700 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Language: en-US-large Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: On 10/1/18 7:35 AM, Dennis Dalessandro wrote: > On 9/28/2018 11:12 PM, John Hubbard wrote: >> On 9/28/18 8:39 AM, Jason Gunthorpe wrote: >>> On Thu, Sep 27, 2018 at 10:39:47PM -0700, john.hubbard@gmail.com wrote: >>>> From: John Hubbard >> [...] >>>> >>>> diff --git a/drivers/infiniband/core/umem.c b/drivers/infiniband/core/= umem.c >>>> index a41792dbae1f..9430d697cb9f 100644 >>>> +++ b/drivers/infiniband/core/umem.c >>>> @@ -60,7 +60,7 @@ static void __ib_umem_release(struct ib_device *dev,= struct ib_umem *umem, int d >>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 page =3D sg_pag= e(sg); >>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if (!PageDirty(= page) && umem->writable && dirty) >>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0 set_page_dirty_lock(page); >>>> -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 put_page(page); >>>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 put_user_page(page); >>> >>> Would it make sense to have a release/put_user_pages_dirtied to absorb >>> the set_page_dity pattern too? I notice in this patch there is some >>> variety here, I wonder what is the right way? >>> >>> Also, I'm told this code here is a big performance bottleneck when the >>> number of pages becomes very long (think >> GB of memory), so having a >>> future path to use some kind of batching/threading sound great. >>> >> >> Yes. And you asked for this the first time, too. Consistent! :) Sorry fo= r >> being slow to pick it up. It looks like there are several patterns, and >> we have to support both set_page_dirty() and set_page_dirty_lock(). So >> the best combination looks to be adding a few variations of >> release_user_pages*(), but leaving put_user_page() alone, because it's >> the "do it yourself" basic one. Scatter-gather will be stuck with that. >> >> Here's a differential patch with that, that shows a nice little cleanup = in >> a couple of IB places, and as you point out, it also provides the hooks = for >> performance upgrades (via batching) in the future. >> >> Does this API look about right? >=20 > I'm on board with that and the changes to hfi1 and qib. >=20 > Reviewed-by: Dennis Dalessandro Hi Dennis, thanks for the review! I'll add those new routines in and send out a v2 soon, now that it appears,= from=20 the recent discussion, that this aspect of the approach is still viable. thanks, --=20 John Hubbard NVIDIA