From: Tim Chen <tim.c.chen@linux.intel.com>
To: Dave Hansen <dave@sr71.net>
Cc: linux-kernel@vger.kernel.org, dave.hansen@linux.intel.com,
peterz@infradead.org, mingo@redhat.com, ak@linux.intel.com,
akpm@linux-foundation.org, cl@linux.com, penberg@kernel.org,
linux-mm@kvack.org, kirill@shutemov.name, lauraa@codeaurora.org
Subject: Re: [PATCH] [v3] warn on performance-impacting configs aka. TAINT_PERFORMANCE
Date: Fri, 22 Aug 2014 11:12:40 -0700 [thread overview]
Message-ID: <1408731160.4347.26.camel@schen9-DESK> (raw)
In-Reply-To: <53F773A2.7040904@sr71.net>
On Fri, 2014-08-22 at 09:45 -0700, Dave Hansen wrote:
> On 08/22/2014 09:32 AM, Tim Chen wrote:
> >> > +#ifdef CONFIG_DEBUG_OBJECTS_FREE
> >> > + "DEBUG_OBJECTS_FREE",
> >> > +#endif
> >> > +#ifdef CONFIG_DEBUG_KMEMLEAK
> >> > + "DEBUG_KMEMLEAK",
> >> > +#endif
> >> > +#ifdef CONFIG_DEBUG_PAGEALLOC
> >> > + "DEBUG_PAGEALLOC",
> > I think coverage profiling also impact performance.
> > So I sould also put CONFIG_GCOV_KERNEL in the list.
>
> Would CONFIG_GCOV_PROFILE_ALL be the better one to check? With plain
> GCOV_KERNEL, I don't think we will, by default, put the coverage
> information in any files and slow them down.
CONFIG_GCOV_PROFILE_ALL is definitely a no no regarding to
performance impact, which is mentioned in the gcov documentation.
I haven't tested this, but if profiling is turned on only for
a piece of code that is performance critical but not for
the whole kernel, in theory performance can still be impacted
with the overhead. So I think it is safer to check
for CONFIG_GCOV_KERNEL, that has no reason to be turned on
for any workload that's performance critical.
Tim
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prev parent reply other threads:[~2014-08-22 18:12 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-08-21 20:24 Dave Hansen
2014-08-21 20:57 ` Dave Jones
2014-08-21 21:03 ` Dave Hansen
2014-08-22 7:20 ` Ingo Molnar
2014-08-22 15:02 ` Dave Hansen
2014-08-24 14:49 ` Ingo Molnar
2014-08-24 20:40 ` Dave Hansen
2014-08-24 22:13 ` Linus Torvalds
2014-08-22 16:32 ` Tim Chen
2014-08-22 16:45 ` Dave Hansen
2014-08-22 18:12 ` Tim Chen [this message]
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