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Date: Tue, 20 May 2014 17:06:17 +0000 From: "Rustad, Mark D" <mark.d.rustad@...el.com> To: Andi Kleen <ak@...ux.intel.com> CC: Andi Kleen <andi@...stfloor.org>, "Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>, "<linux-kernel@...r.kernel.org>" <linux-kernel@...r.kernel.org>, "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>, Netdev <netdev@...r.kernel.org> Subject: Re: [PATCH 1/8] ixgbe: Out of line ixgbe_read/write_reg On May 19, 2014, at 4:25 PM, Andi Kleen <ak@...ux.intel.com> wrote: > On Mon, May 19, 2014 at 10:00:52PM +0000, Rustad, Mark D wrote: >> On May 16, 2014, at 2:43 PM, Andi Kleen <andi@...stfloor.org> wrote: >> >>> From: Andi Kleen <ak@...ux.intel.com> >>> >>> ixgbe_read_reg and ixgbe_write_reg are frequently called and are very big >>> because they have complex error handling code. >> >> Actually, this patch doesn't do anything to ixgbe_write_reg, which would almost certainly be very bad for performance, but instead changes ixgbe_write_reg64. > > I doubt a few cycles around the write make a lot of difference for MMIO. MMIO is dominated > by other things. > >> The latter is not in a performance-sensitive path, but is only called from one site, so there is little reason to take it out-of-line. > > True I moved the wrong one. > > ixgbe_write_reg 3305 (0.00%) 8 409 > > >> I already have a patch in queue to make ixgbe_read_reg out-of-line, because it does have a very costly memory footprint inline, as you have found. > > Please move write_reg too. I will take a look at moving most of them out-of-line. There are just a few in very hot paths that should remain inline. -- Mark Rustad, Networking Division, Intel Corporation -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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