On Wed, Jun 17, 2015 at 7:54 AM, Dan Williams <[email protected]> wrote: > On Wed, Jun 17, 2015 at 4:31 AM, Christoph Hellwig <[email protected]> wrote: >> This mess with arch_ methods and an ops vecor is almost unreadable. >> >> What's the problem with having something like: >> >> pmem_foo() >> { >> if (arch_has_pmem) // or sync_pmem >> arch_pmem_foo(); >> generic_pmem_foo(); >> } >> >> This adds a branch at runtime, but that shoudn't really be any slower >> than an indirect call on architectures that matter. > > No doubt it's premature optimization, but it bothered me that we'll > end up calling cpuid perhaps multiple times every i/o. If it's just a > readability concern I could wrap it in helpers. Getting it upstream > is my primary concern at this point so I have no strong attachment to > the indirect calls if that's all that is preventing an ack.
A cpuid per i/o would be a killer, but the cpufeature code is way smarter than that. You want static_cpu_has, though -- it's even faster, since it gets patched at boot time. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
