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[200.236.242.115]) by smtp.gmail.com with ESMTPSA id q47sm9765744qta.16.2020.06.26.08.23.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 26 Jun 2020 08:23:33 -0700 (PDT) Message-ID: <14da928d1cae8779a93228455c4873c127eeffa6.camel@gmail.com> Subject: Re: [PATCH v2 5/6] powerpc/pseries/iommu: Make use of DDW even if it does not map the partition From: Leonardo Bras To: Michael Ellerman , Benjamin Herrenschmidt , Paul Mackerras , Alexey Kardashevskiy , Thiago Jung Bauermann , Ram Pai Date: Fri, 26 Jun 2020 12:23:28 -0300 In-Reply-To: <20200624062411.367796-6-leobras.c@gmail.com> References: <20200624062411.367796-1-leobras.c@gmail.com> <20200624062411.367796-6-leobras.c@gmail.com> Organization: IBM Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.34.4 (3.34.4-1.fc31) MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Wed, 2020-06-24 at 03:24 -0300, Leonardo Bras wrote: > As of today, if a DDW is created and can't map the whole partition, it's > removed and the default DMA window "ibm,dma-window" is used instead. > > Usually this DDW is bigger than the default DMA window, so it would be > better to make use of it instead. > > Signed-off-by: Leonardo Bras > --- I tested this change with a 256GB DDW which did not map the whole partition, with a MT27700 Family [ConnectX-4 Virtual Function]. I noticed the performance improvement is about the same as using DDW with IOMMU bypass. 64 thread write throughput: +203.0% 64 thread read throughput: +17.5% 1 thread write throughput: +20.5% 1 thread read throughput: +3.43% Averag e write latency: -23.0% Average read latency: -2.26%