Date: Mon, 1 Jan 2018 12:36:55 +0200 From: Konstantin Belousov <kostikbel@gmail.com> To: David Chisnall <theraven@FreeBSD.org> Cc: Adrian Chadd <adrian.chadd@gmail.com>, blubee blubeeme <gurenchan@gmail.com>, FreeBSD current <freebsd-current@freebsd.org> Subject: Re: Programmatically cache line Message-ID: <20180101103655.GF1684@kib.kiev.ua> In-Reply-To: <08038E36-9679-4286-9083-FCEDD637ADCC@FreeBSD.org> References: <CALM2mEmWYz5nyqvxMJwMWoFOXnDTvWFrEug7UUha6xe7Um6ODw@mail.gmail.com> <20171230082812.GL1684@kib.kiev.ua> <CAJ-VmomxGJsn8eOtWoqevdW-spUPgcSGKEc7eR4xuXLP-E1XRA@mail.gmail.com> <08038E36-9679-4286-9083-FCEDD637ADCC@FreeBSD.org>
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On Mon, Jan 01, 2018 at 06:52:37AM +0000, David Chisnall wrote: > On 1 Jan 2018, at 05:09, Adrian Chadd <adrian.chadd@gmail.com> wrote: > > > > On 30 December 2017 at 00:28, Konstantin Belousov <kostikbel@gmail.com> wrote: > >> On Sat, Dec 30, 2017 at 07:50:19AM +0000, blubee blubeeme wrote: > >>> Is there some way to programmatically get the CPU cache line sizes on > >>> FreeBSD? > >> > >> There are, all of them are MD. > >> > >> On x86, the CPUID instruction leaf 0x1 returns the information in > >> %ebx register. > > > > Hm, weird. Why don't we extend sysctl to include this info? For the same reason we do not provide a sysctl to add two integers. > > It would be nice to expose this kind of information via VDSO or similar. There are a lot of similar bits of info that people want to use for ifunc and, SVE is going to have a bunch of similar requirements. > Is VDSO a new trendy word ? ifunc resolvers in usermode on FreeBSD/x86 get four arguments which are essentially cpu_features / cpu_features2 / cpu_stdext_features / cpu_stdext_features2. I suspect that only FreeBSD/x86 arches have the ifunc support, in rtld and coming shortly in kernel. Recently HW_CAP/HW_CAP2 were added to the ELF auxv, and elf_aux_info(3) interface exported from libc. ARM* did not implemented yet the ifunc stubs in rtld. I believe this is considered a low priority because there is no ready to use toolchain which allow to utilize ifuncs on FreeBSD, except if you use recent bfd ld externally.home | help
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