From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 16 Apr 2015 14:26:19 +0200 From: "Mariusz Janiak" Message-ID: <552faa6bf2d134.92118662@wp.pl> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-2" Content-Transfer-Encoding: quoted-printable Subject: Re: [Xenomai] Rtnet e1000e 82583: slow writel(tx_ring->tail), takes above 1us? List-Id: Discussions about the Xenomai project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Zhoupeng Cc: xenomai Dnia Czwartek, 16 Kwietnia 2015 13:30 Zhoupeng napisa= =B3(a) = > I'm using Rtnet with 82583 ethernet card. > It takes about 2us to send AF_PACKET using rt_dev_sendmsg(), about 200 by= tes of data. > = > It is pretty fast, but I want to find what takes so long. > At last I find that "writel(tx_ring->tail)" spend above 1us to complet= e. > = > This is just MMIO write to 82583, of course MMIO is uncache. > And PCIE ASPM is disabled, so L0s is not the problem. > = > I think PCIE Memory Write TLPs is fast enough, but why spend so much time? Hi, There is an interesting article that may be relevant to this issue "PCI Express as a Killer of Software-based Real-Time Ethernet" You can find copy in the attachment. = Best Mariusz = > thanks, > _______________________________________________ > Xenomai mailing list > Xenomai@xenomai.org > http://www.xenomai.org/mailman/listinfo/xenomai -------------- next part -------------- A non-text attachment was scrubbed... Name: rteth_hw_eval.pdf Type: application/x-unknown Size: 875870 bytes Desc: not available URL: