linux-kernel - Re: [PATCH RFC] x86: enforce inlining for atomics

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Date:	Wed, 22 Apr 2015 07:24:41 +0200
From:	Markus Trippelsdorf <markus@...ppelsdorf.de>
To:	Hagen Paul Pfeifer <hagen@...u.net>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Borislav Petkov <bp@...en8.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH RFC] x86: enforce inlining for atomics

On 2015.04.22 at 00:57 +0200, Hagen Paul Pfeifer wrote:
> We see ordinary "template" reuse of common driver code without renaming the
> copied static's. But compiled with CONFIG_OPTIMIZE_INLINING=y the inlining is
> not respected by gcc:
> 
>             atomic_inc: 544 duplicates
>        rcu_read_unlock: 453 duplicates
>          rcu_read_lock: 383 duplicates
>            get_dma_ops: 271 duplicates
> arch_local_irq_restore: 258 duplicates
>             atomic_dec: 215 duplicates
>                kzalloc: 185 duplicates
>       test_and_set_bit: 156 duplicates
>          cpumask_check: 148 duplicates
>           cpumask_next: 146 duplicates
>               list_del: 131 duplicates
>               kref_get: 126 duplicates
>     test_and_clear_bit: 122 duplicates
>                 brelse: 122 duplicates
>          schedule_work: 122 duplicates
>    netif_tx_stop_queue: 115 duplicates
>    atomic_dec_and_test: 107 duplicates
>      dma_mapping_error: 105 duplicates
>          list_del_init: 101 duplicates
>       netif_stop_queue: 100 duplicates
>  arch_local_save_flags:  98 duplicates
>       tasklet_schedule:  76 duplicates
>     clk_prepare_enable:  71 duplicates
>        init_completion:  69 duplicates
>          pskb_may_pull:  67 duplicates
>                   [...]
> 
> Again, the used gcc version is "gcc (Debian 4.9.2-10) 4.9.2". So it is not
> outdated nor a legacy one. The inline heuristic seems really broken for some
> parts. Is it possible that gcc is bedeviled because of inline assembler
> parts which brings confuse the internal scoring system?

I cannot reproduce this issue with my config with 4.8, 4.9 or 5. Could
you please come up with a small testcase and open a gcc bug (with full
gcc command line)?

-- 
Markus
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