From: "Michael S. Tsirkin" <mst@redhat.com>
To: Wanpeng Li <kernellwp@gmail.com>
Cc: Yang Zhang <yang.zhang.wz@gmail.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
kvm <kvm@vger.kernel.org>, Wanpeng Li <wanpeng.li@hotmail.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Radim Krcmar <rkrcmar@redhat.com>,
David Matlack <dmatlack@google.com>,
Alexander Graf <agraf@suse.de>,
Peter Zijlstra <peterz@infradead.org>,
linux-doc@vger.kernel.org
Subject: Re: [RFC PATCH v2 0/7] x86/idle: add halt poll support
Date: Tue, 29 Aug 2017 17:36:32 +0300 [thread overview]
Message-ID: <20170829172929-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <CANRm+CzrNVNcoM5MWwcGbzBF+ZU=Z7ibhFL_9V3RcPjsuPSTgw@mail.gmail.com>
On Tue, Aug 29, 2017 at 10:02:15PM +0800, Wanpeng Li wrote:
> Actually I'm not sure how much sense it makes to introduce this pv
> stuff and the duplicate adaptive halt-polling logic as what has
> already been done in kvm w/o obvious benefit for real workload like
> netperf.
In fact, I would really like to better understand why does the polling
in kvm even help. Switching to the idle task is supposed to be really
cheap as you are not losing context. In case of e.g. network polling
you gain the interrupt latency, but in case of kvm it's just an IPI
which is converted to a memory write when using mwait. Is mwait more
costly than commonly thought? Or is the idle driver too agressive in
putting the CPU into deep sleep?
I think this analysis is something that would benefit
bare-metal/containers as well.
--
MST
next prev parent reply other threads:[~2017-08-29 14:36 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-29 11:46 [RFC PATCH v2 0/7] x86/idle: add halt poll support Yang Zhang
2017-08-29 11:46 ` [RFC PATCH v2 1/7] x86/paravirt: Add pv_idle_ops to paravirt ops Yang Zhang
2017-08-29 13:55 ` Konrad Rzeszutek Wilk
2017-08-30 7:33 ` Juergen Gross
2017-09-01 6:50 ` Yang Zhang
2017-08-29 11:46 ` [RFC PATCH v2 2/7] KVM guest: register kvm_idle_poll for pv_idle_ops Yang Zhang
2017-08-29 11:46 ` [RFC PATCH v2 3/7] sched/idle: Add poll before enter real idle path Yang Zhang
2017-08-29 12:45 ` Peter Zijlstra
2017-09-01 5:57 ` Quan Xu
2017-09-14 8:41 ` Quan Xu
2017-09-14 9:18 ` Borislav Petkov
2017-08-29 14:39 ` Borislav Petkov
2017-09-01 6:49 ` Quan Xu
2017-09-29 10:39 ` Quan Xu
2017-08-29 11:46 ` [RFC PATCH v2 4/7] x86/paravirt: Add update in x86/paravirt pv_idle_ops Yang Zhang
2017-08-29 11:46 ` [RFC PATCH v2 5/7] Documentation: Add three sysctls for smart idle poll Yang Zhang
2017-08-29 17:20 ` Luis R. Rodriguez
2017-08-29 11:46 ` [RFC PATCH v2 6/7] KVM guest: introduce smart idle poll algorithm Yang Zhang
2017-08-29 11:46 ` [RFC PATCH v2 7/7] sched/idle: update poll time when wakeup from idle Yang Zhang
2017-08-29 12:46 ` Peter Zijlstra
2017-09-01 7:30 ` Yang Zhang
2017-09-29 10:29 ` Quan Xu
2017-08-29 11:58 ` [RFC PATCH v2 0/7] x86/idle: add halt poll support Alexander Graf
2017-09-01 6:21 ` Yang Zhang
2017-08-29 13:03 ` Andi Kleen
2017-08-29 14:02 ` Wanpeng Li
2017-08-29 14:27 ` Konrad Rzeszutek Wilk
2017-08-29 14:36 ` Michael S. Tsirkin [this message]
2017-09-01 6:32 ` Yang Zhang
2017-09-01 6:52 ` Wanpeng Li
2017-09-01 6:44 ` Yang Zhang
2017-09-01 6:58 ` Wanpeng Li
2017-09-01 7:53 ` Yang Zhang
2017-08-29 14:56 ` Michael S. Tsirkin
2017-09-13 11:56 ` Yang Zhang
2017-09-14 8:36 ` Quan Xu
2017-09-14 9:19 ` Wanpeng Li
2017-09-14 9:40 ` Quan Xu
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