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[178.94.201.59]) by smtp.gmail.com with ESMTPSA id h10sm3937299ljm.9.2019.05.29.02.58.17 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 29 May 2019 02:58:18 -0700 (PDT) Date: Wed, 29 May 2019 12:58:16 +0300 From: Ivan Khoronzhuk To: Jesper Dangaard Brouer Cc: grygorii.strashko@ti.com, hawk@kernel.org, davem@davemloft.net, ast@kernel.org, linux-kernel@vger.kernel.org, linux-omap@vger.kernel.org, xdp-newbies@vger.kernel.org, ilias.apalodimas@linaro.org, netdev@vger.kernel.org, daniel@iogearbox.net, jakub.kicinski@netronome.com, john.fastabend@gmail.com Subject: Re: [PATCH net-next 3/3] net: ethernet: ti: cpsw: add XDP support Message-ID: <20190529095814.GA4639@khorivan> Mail-Followup-To: Jesper Dangaard Brouer , grygorii.strashko@ti.com, hawk@kernel.org, davem@davemloft.net, ast@kernel.org, linux-kernel@vger.kernel.org, linux-omap@vger.kernel.org, xdp-newbies@vger.kernel.org, ilias.apalodimas@linaro.org, netdev@vger.kernel.org, daniel@iogearbox.net, jakub.kicinski@netronome.com, john.fastabend@gmail.com References: <20190523182035.9283-1-ivan.khoronzhuk@linaro.org> <20190523182035.9283-4-ivan.khoronzhuk@linaro.org> <20190529101659.2aa714b8@carbon> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20190529101659.2aa714b8@carbon> 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 Wed, May 29, 2019 at 10:16:59AM +0200, Jesper Dangaard Brouer wrote: >On Thu, 23 May 2019 21:20:35 +0300 >Ivan Khoronzhuk wrote: > >> +static struct page *cpsw_alloc_page(struct cpsw_common *cpsw) >> +{ >> + struct page_pool *pool = cpsw->rx_page_pool; >> + struct page *page, *prev_page = NULL; >> + int try = pool->p.pool_size << 2; >> + int start_free = 0, ret; >> + >> + do { >> + page = page_pool_dev_alloc_pages(pool); >> + if (!page) >> + return NULL; >> + >> + /* if netstack has page_pool recycling remove the rest */ >> + if (page_ref_count(page) == 1) >> + break; >> + >> + /* start free pages in use, shouldn't happen */ >> + if (prev_page == page || start_free) { >> + /* dma unmap/puts page if rfcnt != 1 */ >> + page_pool_recycle_direct(pool, page); >> + start_free = 1; >> + continue; >> + } >> + >> + /* if refcnt > 1, page has been holding by netstack, it's pity, >> + * so put it to the ring to be consumed later when fast cash is >> + * empty. If ring is full then free page by recycling as above. >> + */ >> + ret = ptr_ring_produce(&pool->ring, page); > >This looks very wrong to me! First of all you are manipulation >directly with the internal pool->ring and not using the API, which >makes this code un-maintainable. Yes I know, it's hack, it was with assumption to be dropped once page_pool recycling is added. >Second this is wrong, as page_pool >assume the in-variance that pages on the ring have refcnt==1. Yes, but this is w/o obvious reason, seems like it can work with refcnt > 1 if remove restriction and use >= instead of ==. As I answered on Ilias comment, I'm going to leave version from RFC and drop this one. > >> + if (ret) { >> + page_pool_recycle_direct(pool, page); >> + continue; >> + } >> + >> + if (!prev_page) >> + prev_page = page; >> + } while (try--); >> + >> + return page; >> +} > > >-- >Best regards, > Jesper Dangaard Brouer > MSc.CS, Principal Kernel Engineer at Red Hat > LinkedIn: http://www.linkedin.com/in/brouer -- Regards, Ivan Khoronzhuk