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Shutemov" To: "Aneesh Kumar K.V" Cc: Peter Zijlstra , Leonardo Bras , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, kvm-ppc@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , Arnd Bergmann , Christophe Leroy , Nicholas Piggin , Andrew Morton , Mahesh Salgaonkar , Reza Arbab , Santosh Sivaraj , Balbir Singh , Thomas Gleixner , Greg Kroah-Hartman , Mike Rapoport , Allison Randal , Jason Gunthorpe , Dan Williams , Vlastimil Babka , Christoph Lameter , Logan Gunthorpe , Andrey Ryabinin , Alexey Dobriyan , Souptick Joarder , Mathieu Desnoyers , Ralph Campbell , Jesper Dangaard Brouer , Jann Horn , Davidlohr Bueso , Ingo Molnar , Christian Brauner , Michal Hocko , Elena Reshetova , Roman Gushchin , Andrea Arcangeli , Al Viro , "Dmitry V. Levin" , =?utf-8?B?SsOpcsO0bWU=?= Glisse , Song Liu , Bartlomiej Zolnierkiewicz , Ira Weiny , "Kirill A. Shutemov" , John Hubbard , Keith Busch Subject: Re: [PATCH v5 01/11] asm-generic/pgtable: Adds generic functions to monitor lockless pgtable walks Message-ID: <20191008144706.yu6jrthweyn4kgdm@box> References: <20191003013325.2614-1-leonardo@linux.ibm.com> <20191003013325.2614-2-leonardo@linux.ibm.com> <20191003071145.GM4536@hirez.programming.kicks-ass.net> <20191003115141.GJ4581@hirez.programming.kicks-ass.net> <651856af-30de-15ad-2312-158f3ad5292e@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <651856af-30de-15ad-2312-158f3ad5292e@linux.ibm.com> User-Agent: NeoMutt/20180716 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Sat, Oct 05, 2019 at 02:05:29PM +0530, Aneesh Kumar K.V wrote: > MADV_DONTNEED has caused us multiple issues due to the fact that it can run > in parallel to page fault. I am not sure whether we have a known/noticeable > performance gain in allowing that with mmap_sem held in read mode. Yes we do. MADV_DONTNEED used a lot by userspace memory allocators and it will be very noticible performance regression if we would switch it to down_write(mmap_sem). -- Kirill A. Shutemov