Date: Thu, 26 Oct 2017 20:10:36 +1100 From: "Tobin C. Harding" <me@...in.cc> To: Greg KH <gregkh@...uxfoundation.org> Cc: "Jason A. Donenfeld" <Jason@...c4.com>, kernel-hardening@...ts.openwall.com, Theodore Ts'o <tytso@....edu>, Linus Torvalds <torvalds@...ux-foundation.org>, Kees Cook <keescook@...omium.org>, Paolo Bonzini <pbonzini@...hat.com>, Tycho Andersen <tycho@...ker.com>, "Roberts, William C" <william.c.roberts@...el.com>, Tejun Heo <tj@...nel.org>, Jordan Glover <Golden_Miller83@...tonmail.ch>, Petr Mladek <pmladek@...e.com>, Joe Perches <joe@...ches.com>, Ian Campbell <ijc@...lion.org.uk>, Sergey Senozhatsky <sergey.senozhatsky@...il.com>, Catalin Marinas <catalin.marinas@....com>, Will Deacon <wilal.deacon@....com>, Steven Rostedt <rostedt@...dmis.org>, Chris Fries <cfries@...gle.com>, Dave Weinstein <olorin@...gle.com>, Daniel Micay <danielmicay@...il.com>, Djalal Harouni <tixxdz@...il.com>, LKML <linux-kernel@...r.kernel.org> Subject: Re: [PATCH v7] printk: hash addresses printed with %p On Thu, Oct 26, 2017 at 09:00:03AM +0200, Greg KH wrote: > On Thu, Oct 26, 2017 at 12:59:08AM +0200, Jason A. Donenfeld wrote: > > On Thu, Oct 26, 2017 at 12:27 AM, Tobin C. Harding <me@...in.cc> wrote: > > > How good is unlikely()? > > > > It places that branch way at the bottom of the function so that it's > > less likely to pollute the icache. > > But always measure it. Lots of times (old numbers were 90% or so), we > get the marking wrong, so please, always benchmark the thing to verify > it actually is doing what you think it should be doing, otherwise it > could make the code worse. Does this come under 'premature optimization is the root of all evil'? Should we be leaving out things like unlikely() and __read_only until the code has been profiled? thanks, Tobin.
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