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Message-ID: <20160419173833.GB15167@techsingularity.net> Date: Tue, 19 Apr 2016 18:39:26 +0100 From: Mel Gorman <mgorman@...hsingularity.net> To: Jesper Dangaard Brouer <brouer@...hat.com> Cc: Eric Dumazet <eric.dumazet@...il.com>, Saeed Mahameed <saeedm@....mellanox.co.il>, Saeed Mahameed <saeedm@...lanox.com>, "David S. Miller" <davem@...emloft.net>, Linux Netdev List <netdev@...r.kernel.org>, Or Gerlitz <ogerlitz@...lanox.com>, Tal Alon <talal@...lanox.com>, Tariq Toukan <tariqt@...lanox.com>, Eran Ben Elisha <eranbe@...lanox.com>, Achiad Shochat <achiad@...lanox.com>, linux-mm <linux-mm@...ck.org> Subject: Re: [PATCH net-next V2 05/11] net/mlx5e: Support RX multi-packet WQE (Striding RQ) On Tue, Apr 19, 2016 at 06:25:32PM +0200, Jesper Dangaard Brouer wrote: > On Mon, 18 Apr 2016 07:17:13 -0700 > Eric Dumazet <eric.dumazet@...il.com> wrote: > > > On Mon, 2016-04-18 at 16:05 +0300, Saeed Mahameed wrote: > > > On Mon, Apr 18, 2016 at 3:48 PM, Eric Dumazet <eric.dumazet@...il.com> wrote: > > > > On Sun, 2016-04-17 at 17:29 -0700, Eric Dumazet wrote: > > > > > > > >> > > > >> If really you need to allocate physically contiguous memory, have you > > > >> considered converting the order-5 pages into 32 order-0 ones ? > > > > > > > > Search for split_page() call sites for examples. > > > > > > > > > > > > > > Thanks Eric, we are already evaluating split_page as we speak. > > > > > > We did look but could not find any specific alloc_pages API that alloc_pages_exact() > > > allocates many physically contiguous pages with order0 ! so we assume > > > it is ok to use split_page. > > > > Note: I have no idea of split_page() performance : > > Maybe Mel knows? Irrelevant in comparison to the cost of allocating an order-5 pages if one is not already available. > And maybe Mel have an opinion about if this is a good > or bad approach, e.g. will this approach stress the page allocator in a > bad way? > It'll contend on the zone lock minimally but again, irrelevant in comparison to having to reclaim/compact an order-5 page if one is not already free. It'll appear to work well in benchmarks and then fall apart when the system is running for long enough.
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