Date: Sat, 20 Nov 2010 11:54:01 +0200 From: Andriy Gapon <avg@freebsd.org> To: Nate Lawson <nate@root.org> Cc: freebsd-acpi@freebsd.org, freebsd-current@freebsd.org Subject: Re: aperf/mperf Message-ID: <4CE79AB9.1020303@freebsd.org> In-Reply-To: <4CE6CB3E.70009@root.org> References: <4CE29718.2050508@freebsd.org> <D1DB20AD-779E-469B-BFFA-C0BA1A249858@neville-neil.com> <4CE51CDA.6010202@freebsd.org> <AANLkTimcJFL8Y47mTznKz72w0z5%2BVoc9oWrz92kE%2BwQa@mail.gmail.com> <4CE533DE.7010401@freebsd.org> <4CE68C0B.1080007@freebsd.org> <4CE6CB3E.70009@root.org>
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on 19/11/2010 21:08 Nate Lawson said the following: > On 11/19/2010 6:39 AM, Andriy Gapon wrote: >> >> I am thinking about providing two APIs for this. >> >> 1. KPI >> void cpu_get_a_m_perf(u_int cpu, uint64_t *aperf, uint64_t *mperf); >> >> 2. Userland >> sysctl dev.cpu.N.aperf_mperf that returns two UQUAD values. >> >> But I am not sure where to put the code for both APIs. >> Adding another device under cpu seems like an overkill. > > These can be exported as a common interface from cpufreq > (dev,cpu.X.perf_stats) and supplied by the child acpi_perf driver on > each cpu. This suggestion sounds quite appealing. But I have some concerns. What if hardware has the capability, but there is no cpufreq - could these MSRs be still useful? Or are they useful only with cpufreq? Probably the latter... Then, another exotic case - if a driver like est or hwpstate is attached "directly", i.e. there is no acpi_perf/_PSS - would the MSRs be still useful? Not sure. -- Andriy Gapon
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