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From: Peter Zijlstra <peterz@infradead.org>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: torvalds@linux-foundation.org, tglx@linutronix.de, hpa@zytor.com,
	julien.thierry@arm.com, will.deacon@arm.com, luto@amacapital.net,
	mingo@kernel.org, catalin.marinas@arm.com, james.morse@arm.com,
	valentin.schneider@arm.com, brgerst@gmail.com, luto@kernel.org,
	bp@alien8.de, dvlasenk@redhat.com, linux-kernel@vger.kernel.org,
	dvyukov@google.com, rostedt@goodmis.org
Subject: Re: [PATCH 02/25] tracing: Improve "if" macro code generation
Date: Tue, 19 Mar 2019 11:11:23 +0100	[thread overview]
Message-ID: <20190319101123.GX6058@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20190318233720.76j6ywkdulmnhu2o@treble>

On Mon, Mar 18, 2019 at 06:37:20PM -0500, Josh Poimboeuf wrote:
> On Mon, Mar 18, 2019 at 04:38:42PM +0100, Peter Zijlstra wrote:
> > With CONFIG_PROFILE_ALL_BRANCHES, the "if" macro converts the
> > conditional to an array index.  This can cause GCC to create horrible
> > code.  When there are nested ifs, the generated code uses register
> > values to encode branching decisions.
> > 
> > Make it easier for GCC to optimize by keeping the conditional as a
> > conditional rather than converting it to an integer.  This shrinks the
> > generated code quite a bit, and also makes the code sane enough for
> > objtool to understand.
> > 
> > Cc: rostedt@goodmis.org
> > Cc: valentin.schneider@arm.com
> > Cc: luto@amacapital.net
> > Cc: brgerst@gmail.com
> > Cc: catalin.marinas@arm.com
> > Cc: mingo@kernel.org
> > Cc: dvlasenk@redhat.com
> > Cc: will.deacon@arm.com
> > Cc: julien.thierry@arm.com
> > Cc: torvalds@linux-foundation.org
> > Cc: dvyukov@google.com
> > Cc: bp@alien8.de
> > Cc: tglx@linutronix.de
> > Cc: james.morse@arm.com
> > Cc: luto@kernel.org
> > Cc: hpa@zytor.com
> > Reported-by: Peter Zijlstra <peterz@infradead.org>
> > Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> > Link: https://lkml.kernel.org/r/20190307174802.46fmpysxyo35hh43@treble
> 
> Missing "From" me.

Right, sorry, quilt eats that and I sometimes forget to fix up :/

  reply	other threads:[~2019-03-19 10:11 UTC|newest]

Thread overview: 59+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-18 15:38 [PATCH 00/25] objtool: UACCESS validation v4 Peter Zijlstra
2019-03-18 15:38 ` [PATCH 01/25] x86: Make SMAP 64-bit only Peter Zijlstra
2019-03-18 16:58   ` Linus Torvalds
2019-03-18 17:36     ` Peter Zijlstra
2019-03-18 17:51       ` Peter Zijlstra
2019-03-18 18:10         ` Linus Torvalds
2019-03-21 17:12           ` hpa
2019-03-21 17:25           ` Denys Vlasenko
2019-03-21 18:18             ` hpa
2019-03-21 21:03               ` Peter Zijlstra
2019-03-21 18:21             ` Linus Torvalds
2019-03-19 11:16   ` [PATCH 01/25] sched/x86: Save [ER]FLAGS on context switch Peter Zijlstra
2019-03-18 15:38 ` [PATCH 02/25] tracing: Improve "if" macro code generation Peter Zijlstra
2019-03-18 17:41   ` Steven Rostedt
2019-03-18 23:37   ` Josh Poimboeuf
2019-03-19 10:11     ` Peter Zijlstra [this message]
2019-03-20 11:18   ` David Laight
2019-03-20 17:26     ` Linus Torvalds
2019-03-20 17:37       ` David Laight
2019-03-20 17:38         ` Linus Torvalds
2019-03-20 18:18       ` Steven Rostedt
2019-05-09 13:00       ` Steven Rostedt
2019-05-09 16:51         ` Linus Torvalds
2019-05-09 18:29           ` Steven Rostedt
2019-05-09 18:45             ` Josh Poimboeuf
2019-05-09 18:47               ` Josh Poimboeuf
2019-05-09 18:48                 ` Randy Dunlap
2019-05-09 18:57                   ` Josh Poimboeuf
2019-05-09 19:06               ` Steven Rostedt
2019-05-09 19:28                 ` Steven Rostedt
2019-05-09 19:44                   ` Linus Torvalds
2019-03-18 15:38 ` [PATCH 03/25] x86/ia32: Fix ia32_restore_sigcontext AC leak Peter Zijlstra
2019-03-18 15:38 ` [PATCH 04/25] i915,uaccess: Fix redundant CLAC Peter Zijlstra
2019-03-18 15:38 ` [PATCH 05/25] x86/uaccess: Move copy_user_handle_tail into asm Peter Zijlstra
2019-03-18 15:38 ` [PATCH 06/25] x86/uaccess: Fix up the fixup Peter Zijlstra
2019-03-18 15:38 ` [PATCH 07/25] x86/nospec,objtool: Introduce ANNOTATE_IGNORE_ALTERNATIVE Peter Zijlstra
2019-03-18 15:38 ` [PATCH 08/25] x86/uaccess,xen: Suppress SMAP warnings Peter Zijlstra
2019-03-18 15:38 ` [PATCH 09/25] x86/uaccess: Always inline user_access_begin() Peter Zijlstra
2019-03-18 15:38 ` [PATCH 10/25] x86/uaccess,signal: Fix AC=1 bloat Peter Zijlstra
2019-03-18 15:38 ` [PATCH 11/25] x86/uaccess: Introduce user_access_{save,restore}() Peter Zijlstra
2019-03-18 15:38 ` [PATCH 12/25] x86/smap: Ditch __stringify() Peter Zijlstra
2019-03-18 15:38 ` [PATCH 13/25] x86/uaccess,kasan: Fix KASAN vs SMAP Peter Zijlstra
2019-03-18 15:38 ` [PATCH 14/25] x86/uaccess,ubsan: Fix UBSAN " Peter Zijlstra
2019-03-18 15:38 ` [PATCH 15/25] x86/uaccess,ftrace: Fix ftrace_likely_update() " Peter Zijlstra
2019-03-18 15:38 ` [PATCH 16/25] x86/uaccess,kcov: Disable stack protector Peter Zijlstra
2019-03-18 15:38 ` [PATCH 17/25] objtool: Set insn->func for alternatives Peter Zijlstra
2019-03-18 15:38 ` [PATCH 18/25] objtool: Handle function aliases Peter Zijlstra
2019-03-18 15:38 ` [PATCH 19/25] objtool: Rewrite add_ignores() Peter Zijlstra
2019-03-18 15:39 ` [PATCH 20/25] objtool: Add --backtrace support Peter Zijlstra
2019-03-18 15:39 ` [PATCH 21/25] objtool: Rewrite alt->skip_orig Peter Zijlstra
2019-03-18 15:39 ` [PATCH 22/25] objtool: Fix sibling call detection Peter Zijlstra
2019-03-18 15:39 ` [PATCH 23/25] objtool: Add UACCESS validation Peter Zijlstra
2019-03-18 23:51   ` Josh Poimboeuf
2019-05-07 11:52   ` Peter Zijlstra
2019-03-18 15:39 ` [PATCH 24/25] objtool: uaccess PUSHF/POPF support Peter Zijlstra
2019-03-18 15:39 ` [PATCH 25/25] objtool: Add Direction Flag validation Peter Zijlstra
2019-03-18 23:57 ` [PATCH 00/25] objtool: UACCESS validation v4 Josh Poimboeuf
2019-03-19 11:20   ` Peter Zijlstra
2019-03-19 11:17 ` [PATCH 26/25] sched/x86_64: Don't save flags on context switch Peter Zijlstra

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