Date: Sun, 20 Jun 2010 19:09:40 +0300 From: Alexander Motin <mav@FreeBSD.org> To: Andriy Gapon <avg@freebsd.org> Cc: freebsd-acpi@freebsd.org Subject: Re: cpufreq_curr_sysctl: memory allocation Message-ID: <4C1E3D44.6020708@FreeBSD.org> In-Reply-To: <4C1E3AE9.3020505@freebsd.org> References: <4C1E3AE9.3020505@freebsd.org>
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Andriy Gapon wrote: > I noticed that cpufreq_curr_sysctl performs a substantial memory allocation and > deallocation on each call. Its size is CF_MAX_LEVELS * sizeof(*levels), which > is ~24KB. This happens even for read-only calls to just query current level. > And such calls happen quite frequently when powerd is running. Worse is that it not just consumes time, but causes a bunch or TLB flush IPIs on free(). For read-only call it doesn't even needs CF_MAX_LEVELS * sizeof(*levels). sizeof(*levels) seems should be enough there. May be then it fits into some existing UMA zone, minimizing penalty. > I think that this is an unnecessary and avoidable load for VM system. > Couldn't a buffer be preallocated in sc and re-used for the calls? > Even if not, for some reason, then wouldn't it be better to have a dedicated uma > zone for that rather than doing malloc+free? Dedicated rarely used UMA zone may eat much more memory then it is needed on SMP. -- Alexander Motin
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