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Re: [Qemu-devel] [PATCH] i386: turn off l3-cache property by default
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [PATCH] i386: turn off l3-cache property by default |
Date: |
Wed, 29 Nov 2017 06:17:40 +0200 |
On Tue, Nov 28, 2017 at 11:20:27PM +0300, Denis V. Lunev wrote:
> > There's one thing I don't understand in your test case: if you
> > just found out that Linux will behave worse if it assumes that
> > the VCPUs are sharing a L3 cache, why are you configuring a
> > 8-core VCPU topology explicitly?
> >
> > Do you still see a difference in the numbers if you use "-smp 8"
> > with no "cores" and "threads" options?
> >
> This is quite simple. A lot of software licenses are bound to the amount
> of CPU __sockets__. Thus it is mandatory in a lot of cases to set topology
> with 1 socket/xx cores to reduce the amount of money necessary to
> be paid for the software.
This answers the first question but not the second one.
If the answer to the second one is negative, then I don't understand why
changing the default makes sense.
I would expect qemu by default to be as close to emulating a physical
system as possible. If one has to deviate from that for some workloads,
that is fine, but probably not a good default.
--
MST
- Re: [Qemu-devel] [PATCH] i386: turn off l3-cache property by default, (continued)
- Re: [Qemu-devel] [PATCH] i386: turn off l3-cache property by default, Longpeng (Mike), 2017/11/29
- Re: [Qemu-devel] [PATCH] i386: turn off l3-cache property by default, Roman Kagan, 2017/11/29
- Re: [Qemu-devel] [PATCH] i386: turn off l3-cache property by default, Longpeng (Mike), 2017/11/29
- Re: [Qemu-devel] [PATCH] i386: turn off l3-cache property by default, Roman Kagan, 2017/11/29
- Re: [Qemu-devel] [PATCH] i386: turn off l3-cache property by default, Eduardo Habkost, 2017/11/29
- Re: [Qemu-devel] [PATCH] i386: turn off l3-cache property by default,
Michael S. Tsirkin <=
- Re: [Qemu-devel] [PATCH] i386: turn off l3-cache property by default, Roman Kagan, 2017/11/29