From: Anton Blanchard <anton@samba.org>
To: Balbir Singh <bsingharora@gmail.com>
Cc: Christophe LEROY <christophe.leroy@c-s.fr>,
mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH] powerpc/configs: Enable function trace by default
Date: Wed, 19 Apr 2017 21:13:46 +1000 [thread overview]
Message-ID: <20170419211346.5e228370@kryten> (raw)
In-Reply-To: <1492071568.8380.20.camel@gmail.com>
Hi Balbir,
> > FTRACE is quite CPU consumming, shouldn't it really be on by
> > default ?
>
> It does some work at boot to NOP out function entry points at _mcount
> locations. Is that what you are referring to? Or the overhead of the
> code in terms of size? Most distro kernels have tracing on by default.
>
> The rest of the overhead is enablement based.
Unfortunately the overhead is somewhat high without
CONFIG_MPROFILE_KERNEL, and enabling that option will break old
toolchains. It would be great if we could automatically enable it based
on the toolchain.
Even with CONFIG_MPROFILE_KERNEL enabled, we aren't noping out the
redundant mflr at the start of each function.
Anton
next prev parent reply other threads:[~2017-04-19 11:13 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-13 7:03 [PATCH] powerpc/configs: Enable function trace by default Balbir Singh
2017-04-13 7:24 ` Christophe LEROY
2017-04-13 8:19 ` Balbir Singh
2017-04-13 8:41 ` Christophe LEROY
2017-04-13 11:51 ` Balbir Singh
2017-04-19 11:13 ` Anton Blanchard [this message]
2017-04-19 12:50 ` Balbir Singh
2017-04-19 13:46 ` Michael Ellerman
2017-04-13 15:21 ` Naveen N. Rao
2017-08-31 11:35 ` Michael Ellerman
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