on 20/06/2010 19:09 Alexander Motin said the following: > 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.
Yes, exactly, for R/O case only one level structure gets populated. >> 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. I agree, but I hope that a single buffer should be sufficient. As I understand, all sysctl operate under Giant unless specifically flagged otherwise. And I don't see any code to explicitly handle concurrent invocations in cpufreq_curr_sysctl. -- Andriy Gapon _______________________________________________ [email protected] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-acpi To unsubscribe, send any mail to "[email protected]"
