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Shutemov" To: Michal Hocko Cc: "Kirill A. Shutemov" , Yang Shi , Vlastimil Babka , hannes@cmpxchg.org, rientjes@google.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [v2 PATCH -mm] mm: account deferred split THPs into MemAvailable Message-ID: <20190830125304.m6aouvq5ohkerfls@box> References: <20190827120923.GB7538@dhcp22.suse.cz> <20190827121739.bzbxjloq7bhmroeq@box> <20190827125911.boya23eowxhqmopa@box> <20190828075708.GF7386@dhcp22.suse.cz> <20190828140329.qpcrfzg2hmkccnoq@box> <20190828141253.GM28313@dhcp22.suse.cz> <20190828144658.ar4fajfuffn6k2ki@black.fi.intel.com> <20190828160224.GP28313@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190828160224.GP28313@dhcp22.suse.cz> 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 Wed, Aug 28, 2019 at 06:02:24PM +0200, Michal Hocko wrote: > > > > > > Any idea about a bad case? > > > > Not really. > > > > How bad you want it to get? How many processes share the page? Access > > pattern? Locking situation? > > Let's say how hard a regular user can make this? It bumped to ~170 ms if each THP was mapped 5 times. Adding ptl contention (tight loop of MADV_DONTNEED) in 3 processes that maps the page, the time to split bumped to ~740ms. Overally, it's reasonable to take ~100ms per GB of huge pages as rule of thumb. -- Kirill A. Shutemov