From: Thomas Garnier <thgarnie@google.com>
Subject: Re: x86: PIE support and option to extend KASLR randomization
Date: Fri, 25 Aug 2017 08:05:52 -0700
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Cc: Herbert Xu <herbert@gondor.apana.org.au>, "David S . Miller" <davem@davemloft.net>,
	Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, "H . Peter Anvin" <hpa@zytor.com>,
	Peter Zijlstra <peterz@infradead.org>, Josh Poimboeuf <jpoimboe@redhat.com>,
	Arnd Bergmann <arnd@arndb.de>, Matthias Kaehlcke <mka@chromium.org>,
	Boris Ostrovsky <boris.ostrovsky@oracle.com>, Juergen Gross <jgross@suse.com>,
	Paolo Bonzini <pbonzini@redhat.com>, =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= <rkrcmar@redhat.com>,
	Joerg Roedel <joro@8bytes.org>, Tom Lendacky <thomas.lendacky@amd.com>,
	Andy Lutomirski <luto@kernel.org>, Borislav Petkov <bp@suse.de>, Brian Gerst <brgerst@gmail.com>,
	"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>, "Rafael J . Wysocki" <rjw@rjwysocki.net>,
	Len Brown <len.brown@intel.com>, Pavel Machek <pavel@ucw.cz>, Tejun Heo <tj@kernel.org>,
	Christoph La
To: Ingo Molnar <mingo@kernel.org>
In-Reply-To: <20170825080443.tvvr6wzs362cjcuu@gmail.com>

On Fri, Aug 25, 2017 at 1:04 AM, Ingo Molnar <mingo@kernel.org> wrote:
>
> * Thomas Garnier <thgarnie@google.com> wrote:
>
>> With the fix for function tracing, the hackbench results have an
>> average of +0.8 to +1.4% (from +8% to +10% before). With a default
>> configuration, the numbers are closer to 0.8%.
>>
>> On the .text size, with gcc 4.9 I see +0.8% on default configuration
>> and +1.180% on the ubuntu configuration.
>
> A 1% text size increase is still significant. Could you look at the disassembly,
> where does the size increase come from?

I will take a look, in this current iteration I added the .got and
.got.plt so removing them will remove a big (even if they are small,
we don't use them to increase perf).

What do you think about the perf numbers in general so far?

>
> Thanks,
>
>         Ingo


-- 
Thomas