From: Andi Kleen <andi@firstfloor.org>
To: mingo@kernel.org
Cc: hpa@zytor.com, linux-kernel@vger.kernel.org,
peterz@infradead.org, tglx@linutronix.de,
linux-tip-commits@vger.kernel.org
Subject: Re: [tip:perf/core] perf/x86/intel: Clean-up/reduce PEBS code
Date: Fri, 13 Sep 2013 23:18:21 -0700 [thread overview]
Message-ID: <87mwng53ki.fsf@tassilo.jf.intel.com> (raw)
In-Reply-To: <tip-8q6y4davda9aawwv5yxe7klp@git.kernel.org> (tip-bot for Peter Zijlstra's message of "Thu, 12 Sep 2013 11:04:44 -0700")
tip-bot for Peter Zijlstra <tipbot@zytor.com> writes:
> +
> + at = (struct pebs_record_nhm *)(unsigned long)ds->pebs_buffer_base;
> + top = (struct pebs_record_nhm *)(unsigned long)ds->pebs_index;
>
> ds->pebs_index = ds->pebs_buffer_base;
>
> + n = (top - at) / x86_pmu.pebs_record_size;
This adds a full slow division to the PEBS hot path.
Does not seem like a improvement to me.
-Andi
--
ak@linux.intel.com -- Speaking for myself only
next prev parent reply other threads:[~2013-09-14 6:18 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-12 18:04 [tip:perf/core] perf/x86/intel: Clean-up/reduce PEBS code tip-bot for Peter Zijlstra
2013-09-14 6:18 ` Andi Kleen [this message]
2013-09-16 6:07 ` Peter Zijlstra
2013-09-16 6:17 ` H. Peter Anvin
2013-09-16 7:24 ` Peter Zijlstra
2013-09-16 16:09 ` Andi Kleen
2013-09-16 16:03 ` Andi Kleen
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