linux-kernel - Re: [RFC PATCH 0/5] x86: dynamic indirect call promotion

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Message-ID: <84f4e89e-f192-8bc5-2a3b-ba7737d806c5@intel.com>
Date:   Tue, 23 Oct 2018 13:37:32 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Nadav Amit <nadav.amit@...il.com>, Nadav Amit <namit@...are.com>,
        Ingo Molnar <mingo@...hat.com>
Cc:     Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        "H . Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        Borislav Petkov <bp@...en8.de>,
        David Woodhouse <dwmw@...zon.co.uk>
Subject: Re: [RFC PATCH 0/5] x86: dynamic indirect call promotion

On 10/23/18 1:32 PM, Nadav Amit wrote:
>> On 10/17/18 5:54 PM, Nadav Amit wrote:
>>> base		relpoline
>>> 		----		---------
>>> nginx 	22898 		25178 (+10%)
>>> redis-ycsb	24523		25486 (+4%)
>>> dbench	2144		2103 (+2%)
>> Just out of curiosity, which indirect branches are the culprits here for
>> causing the slowdowns?
> So I didn’t try to measure exactly which one. There are roughly 500 that
> actually “run” in my tests.

OK, cool, that's pretty much all I wanted to know, just that there
aren't 3 of them or something for which we need all this infrastructure.