From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Dario Faggioli <dario.faggioli@citrix.com>,
Meng Xu <xumengpanda@gmail.com>
Cc: Ian Campbell <ian.campbell@citrix.com>,
Sisu Xi <xisisu@gmail.com>,
Stefano Stabellini <stefano.stabellini@eu.citrix.com>,
George Dunlap <george.dunlap@eu.citrix.com>,
Ian Jackson <ian.jackson@eu.citrix.com>,
"xen-devel@lists.xen.org" <xen-devel@lists.xen.org>,
Meng Xu <mengxu@cis.upenn.edu>, Chong Li <lichong659@gmail.com>,
Dagaen Golomb <dgolomb@seas.upenn.edu>
Subject: Re: [PATCH RFC v1 4/4] libxc for rt scheduler
Date: Fri, 11 Jul 2014 17:49:14 +0100 [thread overview]
Message-ID: <53C0158A.1050704@citrix.com> (raw)
In-Reply-To: <1405096513.29306.543.camel@Solace>
On 11/07/14 17:35, Dario Faggioli wrote:
>
>> My concern is: Will the former one has worse performance than the
>> later one?
>>
> Well, Xen has its tricks, but yes, I think performing e.g., 8 or 16
> hypercalls in a loop is worse than issueing one returning an array.
As far as hypercalls go, the path to Xen is a long one. From userspace,
a hypercall involves a context switch into the kernel (which is a double
context switch through Xen) and a context switch from the kernel into
Xen, and back again. The return from guest kernel to guest userspace
requires a TLB flush.
So, 6 context switches and a TLB flushes per hypercall (assuming a 64bit
dom0).
Use batches wherever possible, even for 2 items. It will be about twice
as fast as not batching.
~Andrew
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next prev parent reply other threads:[~2014-07-11 16:49 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-11 4:49 Introduce rt real-time scheduler for Xen Meng Xu
2014-07-11 4:49 ` [PATCH RFC v1 1/4] rt: Add rt scheduler to hypervisor Meng Xu
2014-07-11 14:27 ` Dario Faggioli
2014-07-11 14:37 ` Andrew Cooper
2014-07-11 15:21 ` Dario Faggioli
2014-07-11 15:40 ` Andrew Cooper
2014-07-11 15:48 ` Dario Faggioli
2014-07-16 17:05 ` Konrad Rzeszutek Wilk
2014-07-17 10:12 ` Meng Xu
2014-07-17 15:12 ` Dario Faggioli
2014-07-18 5:46 ` Meng Xu
2014-07-18 18:40 ` Konrad Rzeszutek Wilk
2014-07-11 4:49 ` [PATCH RFC v1 2/4] xl for rt scheduler Meng Xu
2014-07-11 11:02 ` Wei Liu
2014-07-11 14:59 ` Meng Xu
2014-07-11 15:07 ` Dario Faggioli
2014-07-11 16:25 ` Meng Xu
2014-07-13 12:58 ` Meng Xu
2014-07-14 7:40 ` Dario Faggioli
2014-07-14 9:31 ` Wei Liu
2014-07-17 15:39 ` Ian Campbell
2014-07-11 4:49 ` [PATCH RFC v1 3/4] libxl " Meng Xu
2014-07-11 11:05 ` Wei Liu
2014-07-11 15:08 ` Dario Faggioli
2014-07-12 18:16 ` Meng Xu
2014-07-14 10:38 ` Dario Faggioli
2014-07-17 15:34 ` Ian Campbell
2014-07-17 15:36 ` Ian Campbell
2014-07-18 11:05 ` Meng Xu
2014-07-11 4:49 ` [PATCH RFC v1 4/4] libxc " Meng Xu
2014-07-11 14:49 ` Dario Faggioli
2014-07-11 16:23 ` Meng Xu
2014-07-11 16:35 ` Dario Faggioli
2014-07-11 16:49 ` Andrew Cooper [this message]
2014-07-12 19:46 ` Meng Xu
2014-07-17 15:29 ` Ian Campbell
2014-07-17 15:34 ` George Dunlap
2014-07-17 22:16 ` Meng Xu
2014-07-18 9:49 ` Dario Faggioli
2014-07-18 9:51 ` Ian Campbell
2014-07-18 12:11 ` Meng Xu
2014-07-18 9:47 ` Ian Campbell
2014-07-18 10:00 ` Dario Faggioli
2014-07-11 10:50 ` Introduce rt real-time scheduler for Xen Wei Liu
2014-07-11 11:06 ` Dario Faggioli
2014-07-11 16:14 ` Meng Xu
2014-07-11 16:19 ` Dario Faggioli
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