linux-kernel - Re: [PATCH 1/1] GCD: add binary GCD algorithm

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: <20140822143117.29474ac2ac8092e27d26660a@linux-foundation.org>
Date:	Fri, 22 Aug 2014 14:31:17 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Zhaoxiu Zeng <zhaoxiu.zeng@...il.com>
Cc:	Ingo Molnar <mingo@...nel.org>, George Spelvin <linux@...izon.com>,
	David Howells <dhowells@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	AKASHI Takahiro <takahiro.akashi@...aro.org>,
	Josh Boyer <jwboyer@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] GCD: add binary GCD algorithm

On Fri, 15 Aug 2014 20:49:16 +0800 Zhaoxiu Zeng <zhaoxiu.zeng@...il.com> wrote:

> Because some architectures (alpha, armv6, etc.) don't provide hardware division,
> the mod operation is slow! Binary GCD algorithm uses simple arithmetic operations,
> it replaces division with arithmetic shifts, comparisons, and subtraction.

I had a look around and it seems that most (all?) gcd() and lcd()
callers are on initialization-time slowpaths.

Do you know of a workload which will significantly benefit from this
change?  If so, by how much?

Otherwise I don't think we can justify the additional maintenance
cost/risk, sorry.

And if we *do* decide to proceed with this patch, we should include a
patch which enables it on as many architectures as possible, so it gets
runtime tested.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/