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[2003:ea:8f08:4500:bd22:3e10:4ffe:63e]) by smtp.googlemail.com with ESMTPSA id p8sm9064956wme.22.2021.08.19.23.10.18 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 19 Aug 2021 23:10:19 -0700 (PDT) Subject: Re: [PATCH net-next 2/2] page_pool: optimize the cpu sync operation when DMA mapping To: Yunsheng Lin , davem@davemloft.net, kuba@kernel.org Cc: hawk@kernel.org, ilias.apalodimas@linaro.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org References: <1629425195-10130-1-git-send-email-linyunsheng@huawei.com> <1629425195-10130-3-git-send-email-linyunsheng@huawei.com> From: Heiner Kallweit Message-ID: Date: Fri, 20 Aug 2021 08:10:14 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: <1629425195-10130-3-git-send-email-linyunsheng@huawei.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 20.08.2021 04:06, Yunsheng Lin wrote: > If the DMA_ATTR_SKIP_CPU_SYNC is not set, cpu syncing is > also done in dma_map_page_attrs(), so set the attrs according > to pool->p.flags to avoid calling dma sync function again. > > Also mark the dma error as the unlikely case While we are at > it. > This shouldn't be needed. dma_mapping_error() will be (most likely) inlined by the compiler, and it includes the unlikely() hint. > Signed-off-by: Yunsheng Lin > --- > net/core/page_pool.c | 11 ++++++----- > 1 file changed, 6 insertions(+), 5 deletions(-) > > diff --git a/net/core/page_pool.c b/net/core/page_pool.c > index 1a69784..8172045 100644 > --- a/net/core/page_pool.c > +++ b/net/core/page_pool.c > @@ -191,8 +191,12 @@ static void page_pool_dma_sync_for_device(struct page_pool *pool, > > static bool page_pool_dma_map(struct page_pool *pool, struct page *page) > { > + unsigned long attrs = DMA_ATTR_SKIP_CPU_SYNC; > dma_addr_t dma; > > + if (pool->p.flags & PP_FLAG_DMA_SYNC_DEV) > + attrs = 0; > + > /* Setup DMA mapping: use 'struct page' area for storing DMA-addr > * since dma_addr_t can be either 32 or 64 bits and does not always fit > * into page private data (i.e 32bit cpu with 64bit DMA caps) > @@ -200,15 +204,12 @@ static bool page_pool_dma_map(struct page_pool *pool, struct page *page) > */ > dma = dma_map_page_attrs(pool->p.dev, page, 0, > (PAGE_SIZE << pool->p.order), > - pool->p.dma_dir, DMA_ATTR_SKIP_CPU_SYNC); > - if (dma_mapping_error(pool->p.dev, dma)) > + pool->p.dma_dir, attrs); > + if (unlikely(dma_mapping_error(pool->p.dev, dma))) > return false; > > page_pool_set_dma_addr(page, dma); > > - if (pool->p.flags & PP_FLAG_DMA_SYNC_DEV) > - page_pool_dma_sync_for_device(pool, page, pool->p.max_len); > - > return true; > } > >