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From: Peter Zijlstra <peterz@infradead.org>
To: Andy Lutomirski <luto@amacapital.net>
Cc: David Ahern <dsahern@gmail.com>, Andi Kleen <andi@firstfloor.org>,
	Stephane Eranian <eranian@google.com>,
	"Yan, Zheng" <zheng.z.yan@intel.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@kernel.org>,
	Arnaldo Carvalho de Melo <acme@infradead.org>
Subject: Re: [PATCH v3 00/14] perf, x86: Haswell LBR call stack support
Date: Wed, 9 Apr 2014 13:48:57 +0200	[thread overview]
Message-ID: <20140409114857.GT11096@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <CALCETrUA_JSDepFnKYsrDD5CQX65k4z_XeSxc4RxmhB2RahBZA@mail.gmail.com>

On Wed, Feb 26, 2014 at 12:26:43PM -0800, Andy Lutomirski wrote:
> Speed.  FPO saves one register (a big deal on x86_32; not so important
> on x86_64) but also saves a few cycles on function entry and exit,
> which is a bigger deal for small functions.

So I though that LTO was supposed to get rid of a lot of the small
function and inline them.

I've also heard that in practise this is very 'hard', and thus we're
still stuck with a gazillion small functions (mostly C++ people suffer
from this).

Can anybody give a concise explanation on why LTO doesn't rid us of
these small functions or point to a web resource that describes the
problem?

  reply	other threads:[~2014-04-09 11:49 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-02-18  6:07 [PATCH v3 00/14] perf, x86: Haswell LBR call stack support Yan, Zheng
2014-02-18  6:07 ` [PATCH v3 01/14] perf, x86: Reduce lbr_sel_map size Yan, Zheng
2014-02-18  6:07 ` [PATCH v3 02/14] perf, core: introduce pmu context switch callback Yan, Zheng
2014-02-18  6:07 ` [PATCH v3 03/14] perf, x86: use context switch callback to flush LBR stack Yan, Zheng
2014-02-18  6:07 ` [PATCH v3 04/14] perf, x86: Basic Haswell LBR call stack support Yan, Zheng
2014-02-18  6:07 ` [PATCH v3 05/14] perf, core: pmu specific data for perf task context Yan, Zheng
2014-02-18  6:07 ` [PATCH v3 06/14] perf, core: always switch pmu specific data during context switch Yan, Zheng
2014-02-18  6:07 ` [PATCH v3 07/14] perf, x86: track number of events that use LBR callstack Yan, Zheng
2014-02-18  6:07 ` [PATCH v3 08/14] perf, x86: allocate space for storing LBR stack Yan, Zheng
2014-02-18  6:07 ` [PATCH v3 09/14] perf, x86: Save/resotre LBR stack during context switch Yan, Zheng
2014-02-18  6:07 ` [PATCH v3 10/14] perf, core: simplify need branch stack check Yan, Zheng
2014-02-18  6:07 ` [PATCH v3 11/14] perf, core: Pass perf_sample_data to perf_callchain() Yan, Zheng
2014-02-18  6:07 ` [PATCH v3 12/14] perf, x86: use LBR call stack to get user callchain Yan, Zheng
2014-02-18  6:07 ` [PATCH v3 13/14] perf, x86: enable LBR callstack when recording callchain Yan, Zheng
2014-02-18  6:07 ` [PATCH v3 14/14] perf, x86: Discard zero length call entries in LBR call stack Yan, Zheng
2014-02-23 19:47 ` [PATCH v3 00/14] perf, x86: Haswell LBR call stack support Stephane Eranian
2014-02-24  1:07   ` Yan, Zheng
2014-02-24  7:14 ` Peter Zijlstra
2014-02-26  2:39 ` Andy Lutomirski
2014-02-26  7:04   ` Stephane Eranian
2014-02-26  8:57     ` Yan, Zheng
2014-02-26 16:03     ` Andy Lutomirski
2014-02-26 18:55       ` Andi Kleen
2014-02-26 18:59         ` Andy Lutomirski
2014-02-26 19:19           ` David Ahern
2014-02-26 19:25             ` Andy Lutomirski
2014-02-26 20:14               ` David Ahern
2014-02-26 20:26                 ` Andy Lutomirski
2014-04-09 11:48                   ` Peter Zijlstra [this message]
2014-04-09 16:48                     ` Andi Kleen
2014-04-09 17:40                       ` Andi Kleen
2014-02-26 20:32                 ` Peter Zijlstra
2014-02-26 20:53                 ` Andi Kleen
2014-02-26 21:15                   ` Peter Zijlstra
2014-02-26 21:33                     ` Andi Kleen
2014-02-26 21:34                   ` David Ahern
2014-02-26 21:42                     ` Andi Kleen
2014-02-27  9:09                       ` Stephane Eranian
2014-02-27 12:35           ` Ingo Molnar
2014-02-27 16:08             ` Andi Kleen

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