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[142.162.115.133]) by smtp.gmail.com with ESMTPSA id 14sm2304346qkr.70.2021.02.10.13.02.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 10 Feb 2021 13:02:43 -0800 (PST) Received: from jgg by mlx with local (Exim 4.94) (envelope-from ) id 1l9wdG-006F9X-H8; Wed, 10 Feb 2021 17:02:42 -0400 Date: Wed, 10 Feb 2021 17:02:42 -0400 From: Jason Gunthorpe To: Joao Martins Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-rdma@vger.kernel.org, Andrew Morton , Doug Ledford , John Hubbard , Matthew Wilcox Subject: Re: [PATCH v3 2/4] mm/gup: decrement head page once for group of subpages Message-ID: <20210210210242.GQ4718@ziepe.ca> References: <20210205204127.29441-1-joao.m.martins@oracle.com> <20210205204127.29441-3-joao.m.martins@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210205204127.29441-3-joao.m.martins@oracle.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Feb 05, 2021 at 08:41:25PM +0000, Joao Martins wrote: > Rather than decrementing the head page refcount one by one, we > walk the page array and checking which belong to the same > compound_head. Later on we decrement the calculated amount > of references in a single write to the head page. To that > end switch to for_each_compound_head() does most of the work. > > set_page_dirty() needs no adjustment as it's a nop for > non-dirty head pages and it doesn't operate on tail pages. > > This considerably improves unpinning of pages with THP and > hugetlbfs: > > - THP > gup_test -t -m 16384 -r 10 [-L|-a] -S -n 512 -w > PIN_LONGTERM_BENCHMARK (put values): ~87.6k us -> ~23.2k us > > - 16G with 1G huge page size > gup_test -f /mnt/huge/file -m 16384 -r 10 [-L|-a] -S -n 512 -w > PIN_LONGTERM_BENCHMARK: (put values): ~87.6k us -> ~27.5k us > > Signed-off-by: Joao Martins > Reviewed-by: John Hubbard > --- > mm/gup.c | 29 +++++++++++------------------ > 1 file changed, 11 insertions(+), 18 deletions(-) Looks fine Reviewed-by: Jason Gunthorpe I was wondering why this only touches the FOLL_PIN path, it would make sense to also use this same logic for release_pages() for (i = 0; i < nr; i++) { struct page *page = pages[i]; page = compound_head(page); if (is_huge_zero_page(page)) continue; Jason