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Re: [Qemu-devel] [PATCH] vl: rework smp_parse
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH] vl: rework smp_parse |
Date: |
Fri, 07 Nov 2014 10:40:14 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.2.0 |
On 07/11/2014 10:29, Andrew Jones wrote:
>> > I think this would cause too many failures in the wild. Perhaps error
>> > out if it is lower, and warn if sockets * cores * threads > max_cpus
>> > since we actually allow hot-plug a thread at a time?
> We'd still have more failures if we choose to error out when it's lower,
> since we currently silently adjust threads in some of those cases, or
> just don't care that the topology doesn't support up to maxcpus in other.
So I guess we need a decent fallback if it doesn't match. Something
like (based also on the reply from Eduardo):
1) always warn if max_cpus % (cores*threads) != 0 || smp_cpus %
(cores*threads) != 0
2) if sockets*cpus*threads < max_cpus, adjust sockets to
DIV_ROUND_UP(max_cpus, cores*threads). If we didn't warn in step 1, do
it now. Give a different, less harsh warning if the cmdline
sockets*cpus*threads did match smp_cpus. In the latter case, the user
_almost_ knows what he was doing.
Not perfect, but it could be something to start from. Adjusting sockets
is better than adjusting threads.
Paolo
> I'm not sure how best to go about modifying the command line semantics
> in a backwards compatible way, other than to just create a new "-smp"
> option. I'm open to all opinions and suggestions.
- [Qemu-devel] [PATCH] vl: rework smp_parse, Andrew Jones, 2014/11/06
- Re: [Qemu-devel] [PATCH] vl: rework smp_parse, Eduardo Habkost, 2014/11/06
- Re: [Qemu-devel] [PATCH] vl: rework smp_parse, Paolo Bonzini, 2014/11/06
- Re: [Qemu-devel] [PATCH] vl: rework smp_parse, Andrew Jones, 2014/11/07
- Re: [Qemu-devel] [PATCH] vl: rework smp_parse,
Paolo Bonzini <=
- Re: [Qemu-devel] [PATCH] vl: rework smp_parse, Andrew Jones, 2014/11/07
- Re: [Qemu-devel] [PATCH] vl: rework smp_parse, Andrew Jones, 2014/11/07
- Re: [Qemu-devel] [PATCH] vl: rework smp_parse, Eduardo Habkost, 2014/11/07
- Re: [Qemu-devel] [PATCH] vl: rework smp_parse, Andrew Jones, 2014/11/07
- Re: [Qemu-devel] [PATCH] vl: rework smp_parse, Eduardo Habkost, 2014/11/07
Re: [Qemu-devel] [PATCH] vl: rework smp_parse, Andrew Jones, 2014/11/07