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: John Hubbard , Jason Gunthorpe , john.hubbard@gmail.com Cc: Matthew Wilcox , Michal Hocko , Christopher Lameter , Dan Williams , Jan Kara , Al Viro , linux-mm@kvack.org, LKML , linux-rdma , linux-fsdevel@vger.kernel.org, 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: Dennis Dalessandro Message-ID: Date: Mon, 1 Oct 2018 10:35:02 -0400 MIME-Version: 1.0 In-Reply-To: <36bc65a3-8c2a-87df-44fc-89a1891b86db@nvidia.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: 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 >>> page = sg_page(sg); >>> if (!PageDirty(page) && umem->writable && dirty) >>> set_page_dirty_lock(page); >>> - put_page(page); >>> + 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 for > 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? I'm on board with that and the changes to hfi1 and qib. Reviewed-by: Dennis Dalessandro