linux-kernel - Re: [RFC][PATCH 0/6] Another go at speculative page faults

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Message-ID: <20141024131440.GZ21513@worktop.programming.kicks-ass.net>
Date:	Fri, 24 Oct 2014 15:14:40 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Lai Jiangshan <laijs@...fujitsu.com>,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	torvalds@...ux-foundation.org, paulmck@...ux.vnet.ibm.com,
	tglx@...utronix.de, akpm@...ux-foundation.org, riel@...hat.com,
	mgorman@...e.de, oleg@...hat.com, mingo@...hat.com,
	minchan@...nel.org, kamezawa.hiroyu@...fujitsu.com,
	viro@...iv.linux.org.uk, dave@...olabs.net,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [RFC][PATCH 0/6] Another go at speculative page faults

On Fri, Oct 24, 2014 at 09:54:23AM +0200, Ingo Molnar wrote:
> 
> * Peter Zijlstra <peterz@...radead.org> wrote:
> 
> > On Thu, Oct 23, 2014 at 06:40:05PM +0800, Lai Jiangshan wrote:
> > > On 10/22/2014 01:56 AM, Peter Zijlstra wrote:
> > > > On Tue, Oct 21, 2014 at 08:09:48PM +0300, Kirill A. Shutemov wrote:
> > > >> It would be interesting to see if the patchset affects non-condended case.
> > > >> Like a one-threaded workload.
> > > > 
> > > > It does, and not in a good way, I'll have to look at that... :/
> > > 
> > > Maybe it is blamed to find_vma_srcu() that it doesn't take the advantage of
> > > the vmacache_find() and cause more cache-misses.
> > 
> > Its what I thought initially, I tried doing perf record with and
> > without, but then I ran into perf diff not quite working for me and I've
> > yet to find time to kick that thing into shape.
> 
> Might be the 'perf diff' regression fixed by this:
> 
>   9ab1f50876db perf diff: Add missing hists__init() call at tool start
> 
> I just pushed it out into tip:master.

I was on tip/master, so unlikely to be that as I was likely already
having it.

perf-report was affected too, for some reason my CONFIG_DEBUG_INFO=y
vmlinux wasn't showing symbols (and I double checked that KASLR crap was
disabled, so that wasn't confusing stuff either).

When I forced perf-report to use kallsyms it works, however perf-diff
doesn't have that option.

So there's two issues there, 1) perf-report failing to generate useful
output and 2) per-diff lacking options to force it to behave.
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