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Date: Thu, 10 Dec 2015 06:51:23 +0100 From: Giuseppe CAVALLARO <peppe.cavallaro@...com> To: David Laight <David.Laight@...LAB.COM>, "netdev@...r.kernel.org" <netdev@...r.kernel.org> CC: "alexandre.torgue@...com" <alexandre.torgue@...com>, Fabrice Gasnier <fabrice.gasnier@...com> Subject: Re: [PATCH (net-next.git) 13/18] stmmac: perf, remove modulo in stmmac_rx() On 12/10/2015 6:11 AM, Giuseppe CAVALLARO wrote: > On 12/9/2015 6:21 PM, David Laight wrote: >> From: Giuseppe Cavallaro >>> Sent: 09 December 2015 08:38 >>> The indexes into the ring buffer are always incremented, and >>> the entry is accessed via doing a modulo to find the "real" index. >>> Modulo is an expensive operation. >>> >>> This patch replaces the modulo with a simple if clamp. >>> It helps improve stmmac RX path as it's being called inside RX loop. >> >> Is dma_rx_size always a power of 2 ? > > no > >> If so you can replace the % by & and remove the conditionals. >> >> If you have changed the read and write values to indexes >> then you need to be certain that the 'ring full' and 'ring empty' >> cases are correctly distinguished. > > this is implicitly managed by dirty and curr index. ... also the dma will fail with unavailable buffer. peppe > > thx > peppe > >> >> David >> > > > -- 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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