netdev - RE: [PATCH (net-next.git) 13/18] stmmac: perf, remove modulo in stmmac

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <063D6719AE5E284EB5DD2968C1650D6D1CBE9BB2@AcuExch.aculab.com>
Date:	Wed, 9 Dec 2015 17:21:34 +0000
From:	David Laight <David.Laight@...LAB.COM>
To:	'Giuseppe Cavallaro' <peppe.cavallaro@...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()

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 ?
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.

	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