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[178.94.201.59]) by smtp.gmail.com with ESMTPSA id m18sm942231ljb.35.2019.04.19.03.42.31 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Fri, 19 Apr 2019 03:42:32 -0700 (PDT) Date: Fri, 19 Apr 2019 13:42:30 +0300 From: Ivan Khoronzhuk To: Ilias Apalodimas Cc: grygorii.strashko@ti.com, linux-omap@vger.kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, hawk@kernel.org, xdp-newbies@vger.kernel.org, ast@kernel.org, aniel@iogearbox.net, jakub.kicinski@netronome.com, john.fastabend@gmail.com Subject: Re: [RFC PATCH 3/3] net: ethernet: ti: cpsw: add XDP support Message-ID: <20190419104228.GA4268@khorivan> Mail-Followup-To: Ilias Apalodimas , grygorii.strashko@ti.com, linux-omap@vger.kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, hawk@kernel.org, xdp-newbies@vger.kernel.org, ast@kernel.org, aniel@iogearbox.net, jakub.kicinski@netronome.com, john.fastabend@gmail.com References: <20190417174942.11811-1-ivan.khoronzhuk@linaro.org> <20190417174942.11811-4-ivan.khoronzhuk@linaro.org> <20190419083156.GA6687@apalos> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20190419083156.GA6687@apalos> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Fri, Apr 19, 2019 at 11:31:56AM +0300, Ilias Apalodimas wrote: >Hi Ivan, > >> +static struct page *cpsw_alloc_page(struct cpsw_common *cpsw) >> +{ >> + struct page_pool *pool = cpsw->rx_page_pool; >> + struct page *page; >> + int i = 0; >> + >> + do { >> + page = page_pool_dev_alloc_pages(pool); >> + if (!page) >> + return NULL; >> + >> + /* skip pages used by skb netstack */ >I think the comment here is wrong and might confuse people. >The page ref cnt is 1, which means the packet was *processed* and netstack is >done with it, hence you can re-use it. >If it's !=1 then you correctly unmap the buffer and decrease the ref cnt, so it >will eventually be freed and not returned to the pool, right? It's compensation substitution for page_pool support in skb netsack. And should be considered in combine with: skb = build_skb(xmeta, cpsw_rxbuf_total_len(pkt_size)); ... page_pool_recycle_direct(pool, page); page_ref_inc(page); netif_receive_skb(skb); Here order is important. I will correct comments in final version (w/o overloading) ofc, leaving thinking environment for people. I think it's fair enough about this. >> + if (page_ref_count(page) == 1) >> + break; >> + >> + /* it's a pitty, but free page */ >> + page_pool_recycle_direct(pool, page); >> + } while (++i < descs_pool_size); >> + >> + return page; >> +} >> + > > /Ilias -- Regards, Ivan Khoronzhuk