Subject: Re: [PATCH v3 1/8] ftrace: Add DYNAMIC_FTRACE_WITH_CALL_OPS
To:     Mark Rutland <mark.rutland@arm.com>
CC:     <linux-arm-kernel@lists.infradead.org>, <catalin.marinas@arm.com>,
        <lenb@kernel.org>, <linux-acpi@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, <mhiramat@kernel.org>,
        <ndesaulniers@google.com>, <ojeda@kernel.org>,
        <peterz@infradead.org>, <rafael.j.wysocki@intel.com>,
        <revest@chromium.org>, <robert.moore@intel.com>,
        <rostedt@goodmis.org>, <will@kernel.org>,
        "liwei (GF)" <liwei391@huawei.com>
References: <20230123134603.1064407-1-mark.rutland@arm.com>
 <20230123134603.1064407-2-mark.rutland@arm.com>
 <f2f5dfc6-3deb-9fce-a9be-9386e844a9cf@huawei.com>
 <Y9ebIY/pWz0Ms9S6@FVFF77S0Q05N>
From:   "Wangshaobo (bobo)" <bobo.shaobowang@huawei.com>
Message-ID: <60ec7607-7c5c-1a6e-18c9-8025cb2f289f@huawei.com>
Date:   Tue, 31 Jan 2023 09:25:51 +0800
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在 2023/1/30 18:25, Mark Rutland 写道:
> On Sat, Jan 28, 2023 at 04:46:48PM +0800, Wangshaobo (bobo) wrote:
>> 锟斤拷 2023/1/23 21:45, Mark Rutland 写锟斤拷:
>>> +config DYNAMIC_FTRACE_WITH_CALL_OPS
>>> +	def_bool y
>>> +	depends on HAVE_DYNAMIC_FTRACE_WITH_CALL_OPS
>>> +
>> Hi Mark,
> 
> Hi,
> 
>> I have test your patches and it looks fine with my sample module,
> 
> Thanks for testing!
> 
>> but here setting DYNAMIC_FTRACE_WITH_CALL_OPS to y immutably may increase the
>> .text section size by 5% or more, how about making this to optional^^
> 
> We could consider making this optional. I had not made this optional so far as
> in the future I'd like to make this the only implementation of ftrace on arm64
> (once we can drop the old mcount version, and once we've sorted out the
> incompatibility with CFI). In the mean time, it probably makes sense to have
> the option at least to enable testing of each of the two forms.
> 
> Is your concern that the overall kernel image size is larger, or do you care
> specifically about the size of the .text section for some reason?
> 
> Thanks,
> Mark
Embedded devices may pay more attention to Image size, and which may 
also indirectly affects performance, for more reason, I think making 
sense to have the option for testing is more important.

-- Wang ShaoBo
> 
>>
>> -- Wang ShaoBo
>>>    config DYNAMIC_FTRACE_WITH_ARGS
>>>    	def_bool y
>>>    	depends on DYNAMIC_FTRACE
>>> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
>>> index 442438b93fe9..e634b80f49d1 100644