Date: Mon, 21 Oct 2013 08:58:33 +0100 From: Mark Robert Vaughan Murray <markm@FreeBSD.org> To: Ian Lepore <ian@FreeBSD.org> Cc: freebsd-arm <freebsd-arm@FreeBSD.org> Subject: Re: ARM counter registers and get_cyclecount() Message-ID: <448247EB-EE2D-438D-81DA-B2D415C14D8A@FreeBSD.org> In-Reply-To: <1382313483.92499.136.camel@revolution.hippie.lan> References: <0D53AF4E-9EC4-42E1-8D9E-1ECB87A9CCE6@FreeBSD.org> <1382306602.92499.117.camel@revolution.hippie.lan> <78B77E93-BE2E-4CA2-9D1B-F994B795FABB@FreeBSD.org> <1382309355.92499.127.camel@revolution.hippie.lan> <25608D4E-C299-498A-8F77-3548D711F419@FreeBSD.org> <1382313483.92499.136.camel@revolution.hippie.lan>
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[-- Attachment #1 --] On 21 Oct 2013, at 00:58, Ian Lepore <ian@FreeBSD.org> wrote: >>> There are other complexities that come to mind... things like clocks >>> that run slower or even stop in power-saving modes, is that a problem? >> >> Yup :-(. But if its fast and the highest-resolution non-quantised timing available, I guess I'll use it. What I don't want is numbers with lots of low bits being non random/skipped; I'd rather have a slower counter still incrementing from the bottom bit up. If its running at CPU/Instruction clock speed, it will do. >> >> M > > On the very newest arm boards I have there are counters that can run as > fast as 66 MHz (cpu runs at 800-1000 MHz). That's by far the fastest > I've seen yet. On older boards it's likely to be a few MHz at best. Yuk :-(. I was hoping for some approximation to 1-increment-per-instruction or close. > It's a pity you don't think the names are important. IMO, the names of > things are at least as important as the implementation (and often more > so, because they're harder to change and that puts a greater premium on > getting them right). I don't think its unimportant; I think it is another thread of conversation. Right now i'm looking for a working counter with the right physical characteristics. What name the beastie gets will likely be apparent when its found/written. M -- Mark R V Murray [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG/MacGPG2 v2.0.20 (Darwin) Comment: GPGTools - http://gpgtools.org iQCVAwUBUmTeqd58vKOKE6LNAQp5iwP8CbSPQ4AtlaUmqBwmR8rGESjXvPZ6HCoF E5e0vw5//1DRNo1soj5uD0JDGSbvar0TPXLv1kbMgl7tWXpv3UmXrmdPnC7nfE+G q/LKN651mVuTLJdxq7iC+uA9qI+Xr3rhVyUL9Ph4mBujQyAT0x4l2Z+J0ZQ/RMOm +w+mjsWwquw= =wY+O -----END PGP SIGNATURE-----home | help
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