From: Jan Beulich <jbeulich@suse.com>
To: "Jürgen Groß" <jgross@suse.com>
Cc: Anthony PERARD <anthony.perard@citrix.com>,
xen-devel@lists.xenproject.org,
Ian Jackson <ian.jackson@eu.citrix.com>, Wei Liu <wl@xen.org>
Subject: Re: [Xen-devel] [PATCH] tools/libxl: make default of max event channels dependant on vcpus
Date: Thu, 26 Mar 2020 11:05:52 +0100 [thread overview]
Message-ID: <e0072cdc-e257-8cd7-bc43-e17baa55934c@suse.com> (raw)
In-Reply-To: <5ecfa9a2-32f1-cac5-da33-842a3e13a01f@suse.com>
On 26.03.2020 11:00, Jürgen Groß wrote:
> On 26.03.20 10:54, Jan Beulich wrote:
>> On 26.03.2020 10:45, Juergen Gross wrote:
>>> Today the maximum number of event channels for a guest is defaulting
>>> to 1023. For large guests with lots of vcpus this is not enough, as
>>> e.g. the Linux kernel uses 7 event channels per vcpu, limiting the
>>> guest to about 140 vcpus.
>>
>> I don't think any particular guest OS should "dictate" the default
>> here. What if another OS (or even a future version of Linux) requires
>> more than 8? And why would the value depend on number of vCPU-s but
>> not number and kind of virtual devices?
>
> It is a rough estimate. And with HVM guests being limited to 128 cpus
> anyway, this problem is more relevant for PV guests, limiting the
> available options for guest OS's.
How many evtchns would e.g. mini-os require? I.e. wouldn't such stubdoms
get a much larger than necessary allowance this way?
Jan
next prev parent reply other threads:[~2020-03-26 10:06 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-26 9:45 [Xen-devel] [PATCH] tools/libxl: make default of max event channels dependant on vcpus Juergen Gross
2020-03-26 9:54 ` Jan Beulich
2020-03-26 10:00 ` Jürgen Groß
2020-03-26 10:05 ` Jan Beulich [this message]
2020-03-26 10:11 ` Jürgen Groß
2020-03-26 10:29 ` Jürgen Groß
2020-03-26 12:36 ` Andrew Cooper
2020-03-26 12:42 ` Jürgen Groß
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