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From: Peter Zijlstra <peterz@infradead.org>
To: Marcelo Tosatti <mtosatti@redhat.com>
Cc: kvm-devel <kvm@vger.kernel.org>,
	linux-kernel@vger.kernel.org,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@kernel.org>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Bandan Das <bsd@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: [PATCH] sched: introduce configurable delay before entering idle
Date: Wed, 8 May 2019 00:15:19 +0200	[thread overview]
Message-ID: <20190507221519.GE2677@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20190507185647.GA29409@amt.cnet>

On Tue, May 07, 2019 at 03:56:49PM -0300, Marcelo Tosatti wrote:
> 
> Certain workloads perform poorly on KVM compared to baremetal
> due to baremetal's ability to perform mwait on NEED_RESCHED
> bit of task flags (therefore skipping the IPI).
> 
> This patch introduces a configurable busy-wait delay before entering the
> architecture delay routine, allowing wakeup IPIs to be skipped 
> (if the IPI happens in that window).
> 
> The real-life workload which this patch improves performance
> is SAP HANA (by 5-10%) (for which case setting idle_spin to 30 
> is sufficient).
> 
> This patch improves the attached server.py and client.py example 
> as follows:
> 
> Host:                           31.814230202231556
> Guest:                          38.17718765199993       (83 %)
> Guest, idle_spin=50us:          33.317709898000004      (95 %)
> Guest, idle_spin=220us:         32.27826551499999       (98 %)
> 
> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

Thanks for the CC..

NAK, this is something that should live in a virt idle governor or
something along those lines.

  reply	other threads:[~2019-05-07 22:15 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-07 18:56 [PATCH] sched: introduce configurable delay before entering idle Marcelo Tosatti
2019-05-07 22:15 ` Peter Zijlstra [this message]
2019-05-07 23:44   ` Marcelo Tosatti
2019-05-13  9:20 ` Wanpeng Li
2019-05-13 11:31   ` Konrad Rzeszutek Wilk
2019-05-13 11:51     ` Raslan, KarimAllah
2019-05-13 12:30       ` Boris Ostrovsky
2019-05-15  1:45       ` Wanpeng Li
2019-05-14 13:50   ` Marcelo Tosatti
2019-05-14 15:20     ` Konrad Rzeszutek Wilk
2019-05-14 17:42       ` Marcelo Tosatti
2019-05-15  1:42         ` Wanpeng Li
2019-05-15 20:26           ` Marcelo Tosatti
2019-05-15 18:42     ` Ankur Arora
2019-05-15 20:43       ` Marcelo Tosatti
2019-05-17  4:32         ` Ankur Arora
2019-05-17 17:49           ` Marcelo Tosatti
2019-05-16  1:07       ` Wanpeng Li
2019-05-17  2:06         ` Ankur Arora

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