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From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: "Cédric Le Goater" <clg@kaod.org>,
	"Alex Bennée" <alex.bennee@linaro.org>
Cc: Nikunj A Dadhania <nikunj@linux.vnet.ibm.com>,
	qemu-ppc@nongnu.org, david@gibson.dropbear.id.au,
	rth@twiddle.net, programmingkidx@gmail.com,
	qemu-devel@nongnu.org, bharata@linux.vnet.ibm.com
Subject: Re: [Qemu-devel] [Qemu-ppc] [PATCH RFC v1 0/3] Enable MTTCG on PPC64
Date: Tue, 11 Apr 2017 23:26:07 +1000	[thread overview]
Message-ID: <1491917167.7236.1.camel@kernel.crashing.org> (raw)
In-Reply-To: <04c9f03f-7f04-ebce-15f1-988db1fb2c1d@kaod.org>

On Tue, 2017-04-11 at 14:28 +0200, Cédric Le Goater wrote:
> I really don't know. 
> 
> Ben, now that we have mttcg activated by default on ppc, it takes 
> a while for the linux kernel to do the early setup. I think we are
> in the code section where we spin loop the secondaries. Most of the
> time is spent in skiboot under cpu_idle/relax.
> 
> Any idea where that could come from ? 
> 
> > See c22edfebff29f63d793032e4fbd42a035bb73e27 for an example.
> 
> Thanks for the hint.

They are spinning, but they have smt_low instructions in the loop,
maybe that causes us to do some kind of synchronization as we exit
the emulation loop on these ? I added that to force relinguish time
to other threads on the pre-MT TCG...

There isn't really such a "pause" instruction. At least not yet.... P9
has a wait that is meant to wait for special AS_Notify cycles but will
also wait for interrupts. We don't have an mwait at this point.

Ben.
 

  reply	other threads:[~2017-04-11 13:26 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-06 10:22 [Qemu-devel] [PATCH RFC v1 0/3] Enable MTTCG on PPC64 Nikunj A Dadhania
2017-04-06 10:22 ` [Qemu-devel] [PATCH RFC v1 1/3] target/ppc: Emulate LL/SC using cmpxchg helpers Nikunj A Dadhania
2017-04-06 15:51   ` Richard Henderson
2017-04-07  5:12     ` Nikunj A Dadhania
2017-04-06 15:53   ` Richard Henderson
2017-04-07  5:14     ` Nikunj A Dadhania
2017-04-07  5:23   ` David Gibson
2017-04-07  5:42     ` Nikunj A Dadhania
2017-04-06 10:22 ` [Qemu-devel] [PATCH RFC v1 2/3] cputlb: handle first atomic write to the page Nikunj A Dadhania
2017-04-06 15:54   ` Richard Henderson
2017-04-06 10:22 ` [Qemu-devel] [PATCH RFC v1 3/3] target/ppc: Generate fence operations Nikunj A Dadhania
2017-04-06 16:15   ` Richard Henderson
2017-04-07  5:21     ` Nikunj A Dadhania
2017-04-07 18:19       ` Richard Henderson
2017-04-06 13:26 ` [Qemu-devel] [Qemu-ppc] [PATCH RFC v1 0/3] Enable MTTCG on PPC64 Cédric Le Goater
2017-04-06 13:28   ` G 3
2017-04-06 13:32     ` Cédric Le Goater
2017-04-06 13:47       ` G 3
2017-04-06 17:08       ` luigi burdo
2017-04-06 18:06         ` G 3
2017-04-07  5:24   ` Nikunj A Dadhania
2017-04-07  6:07     ` Cédric Le Goater
2017-04-10 16:41       ` Cédric Le Goater
2017-04-10 16:44         ` Nikunj A Dadhania
2017-04-10 16:59           ` Cédric Le Goater
2017-04-10 17:07             ` Nikunj A Dadhania
2017-04-10 17:20         ` Alex Bennée
2017-04-11 12:28           ` Cédric Le Goater
2017-04-11 13:26             ` Benjamin Herrenschmidt [this message]
2017-04-11 14:04               ` Alex Bennée

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