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From: Ingo Molnar <mingo@elte.hu>
To: Jan Kiszka <jan.kiszka@siemens.com>
Cc: qemu-devel <qemu-devel@nongnu.org>,
	Anthony Liguori <aliguori@us.ibm.com>, kvm <kvm@vger.kernel.org>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Sasha Levin <levinsasha928@gmail.com>,
	Asias He <asias.hejun@gmail.com>,
	Pekka Enberg <penberg@cs.helsinki.fi>
Subject: Re: [RFC][PATCH] Register Linux dyntick timer as per-thread signal
Date: Thu, 16 Jun 2011 12:26:06 +0200	[thread overview]
Message-ID: <20110616102606.GA24541@elte.hu> (raw)
In-Reply-To: <4DF9CD7E.5020509@siemens.com>


* Jan Kiszka <jan.kiszka@siemens.com> wrote:

> Ingo Molnar pointed out that sending the timer signal to the whole
> process, just blocking it everywhere, is suboptimal with an increasing
> number of threads. QEMU is using this pattern so far.
> 
> But Linux provides a (non-portable) way to restrict the signal to a
> single thread: Use SIGEV_THREAD_ID unless we are forced to emulate
> signalfd via an additional thread. That case could theoretically be
> optimized as well, but it doesn't look worth bothering.

Would be nice to mention it in the changelog that the context and 
motivation for my remark was a patch sent for tools/kvm/ by Asias He:

  kvm tools: Block SIGALRM for vcpu thread using sig_block() helper

Thanks,

	Ingo

WARNING: multiple messages have this Message-ID (diff)
From: Ingo Molnar <mingo@elte.hu>
To: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Anthony Liguori <aliguori@us.ibm.com>, kvm <kvm@vger.kernel.org>,
	Asias He <asias.hejun@gmail.com>,
	qemu-devel <qemu-devel@nongnu.org>,
	Pekka Enberg <penberg@cs.helsinki.fi>,
	Sasha Levin <levinsasha928@gmail.com>,
	Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: [Qemu-devel] [RFC][PATCH] Register Linux dyntick timer as per-thread signal
Date: Thu, 16 Jun 2011 12:26:06 +0200	[thread overview]
Message-ID: <20110616102606.GA24541@elte.hu> (raw)
In-Reply-To: <4DF9CD7E.5020509@siemens.com>


* Jan Kiszka <jan.kiszka@siemens.com> wrote:

> Ingo Molnar pointed out that sending the timer signal to the whole
> process, just blocking it everywhere, is suboptimal with an increasing
> number of threads. QEMU is using this pattern so far.
> 
> But Linux provides a (non-portable) way to restrict the signal to a
> single thread: Use SIGEV_THREAD_ID unless we are forced to emulate
> signalfd via an additional thread. That case could theoretically be
> optimized as well, but it doesn't look worth bothering.

Would be nice to mention it in the changelog that the context and 
motivation for my remark was a patch sent for tools/kvm/ by Asias He:

  kvm tools: Block SIGALRM for vcpu thread using sig_block() helper

Thanks,

	Ingo

  reply	other threads:[~2011-06-16 10:29 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-06-16  9:31 [RFC][PATCH] Register Linux dyntick timer as per-thread signal Jan Kiszka
2011-06-16  9:31 ` [Qemu-devel] " Jan Kiszka
2011-06-16 10:26 ` Ingo Molnar [this message]
2011-06-16 10:26   ` Ingo Molnar
2011-06-16 14:39 ` Richard Henderson
2011-06-16 14:39   ` Richard Henderson
2011-06-16 15:24 ` Alexandre Raymond
2011-06-16 15:24   ` Alexandre Raymond
2011-06-17  9:25   ` Jan Kiszka
2011-06-17  9:25     ` Jan Kiszka
2011-06-17  9:25 ` [PATCH v2] " Jan Kiszka
2011-06-17  9:25   ` [Qemu-devel] " Jan Kiszka
2011-06-17 18:06   ` Richard Henderson
2011-06-17 18:06     ` Richard Henderson
2011-07-23 16:52   ` Anthony Liguori
2011-07-23 16:52     ` [Qemu-devel] " Anthony Liguori

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