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From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Tsutomu OWA <tsutomu.owa@toshiba.co.jp>
Cc: linuxppc-dev@ozlabs.org, Thomas Gleixner <tglx@linutronix.de>,
	mingo@elte.hu, Arnd Bergmann <arnd@arndb.de>,
	linux-kernel@vger.kernel.org
Subject: Re: [patch 4/4] powerpc 2.6.21-rt1: reduce scheduling latency by changing tlb flush size
Date: Tue, 15 May 2007 17:38:27 +1000	[thread overview]
Message-ID: <1179214707.32247.177.camel@localhost.localdomain> (raw)
In-Reply-To: <yyips5261pt.wl@toshiba.co.jp>


> +
> +#ifdef CONFIG_PREEMPT_RT
> +	/*
> +	 * Since flushing tlb needs expensive hypervisor call(s) on celleb,
> +	 * always flush it on RT to reduce scheduling latency.
> +	 */
> +	if (machine_is(celleb)) {
> +		flush_tlb_pending();
> +		return;
> +	}
> +#endif /* CONFIG_PREEMPT_RT */
> +
>  	if (i >= PPC64_TLB_BATCH_NR)
>  		flush_tlb_pending();
>  }

Any reason to do that only on celleb ? :-)

Also, we might want to still batch, though in smaller amount. Have you measured
the time it takes ? We might want to modulate the amount based on wether we
are using native hash tables or an hypervisor.

Ben.

WARNING: multiple messages have this Message-ID (diff)
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Tsutomu OWA <tsutomu.owa@toshiba.co.jp>
Cc: Arnd Bergmann <arnd@arndb.de>,
	linuxppc-dev@ozlabs.org, Thomas Gleixner <tglx@linutronix.de>,
	mingo@elte.hu, linux-kernel@vger.kernel.org
Subject: Re: [patch 4/4] powerpc 2.6.21-rt1: reduce scheduling latency by changing tlb flush size
Date: Tue, 15 May 2007 17:38:27 +1000	[thread overview]
Message-ID: <1179214707.32247.177.camel@localhost.localdomain> (raw)
In-Reply-To: <yyips5261pt.wl@toshiba.co.jp>


> +
> +#ifdef CONFIG_PREEMPT_RT
> +	/*
> +	 * Since flushing tlb needs expensive hypervisor call(s) on celleb,
> +	 * always flush it on RT to reduce scheduling latency.
> +	 */
> +	if (machine_is(celleb)) {
> +		flush_tlb_pending();
> +		return;
> +	}
> +#endif /* CONFIG_PREEMPT_RT */
> +
>  	if (i >= PPC64_TLB_BATCH_NR)
>  		flush_tlb_pending();
>  }

Any reason to do that only on celleb ? :-)

Also, we might want to still batch, though in smaller amount. Have you measured
the time it takes ? We might want to modulate the amount based on wether we
are using native hash tables or an hypervisor.

Ben.



  reply	other threads:[~2007-05-15  7:38 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-05-14  6:22 [patch 0/4] powerpc 2.6.21-rt1: fix build a breakage and some minor issues Tsutomu OWA
2007-05-14  6:26 ` [patch 1/4] powerpc 2.6.21-rt1: fix a build breakage by adding __raw_*_relax() macros Tsutomu OWA
2007-05-14  6:28 ` [patch 2/4] powerpc 2.6.21-rt1: convert spinlocks to raw ones for Celleb Tsutomu OWA
2007-05-14  6:29 ` [patch 3/4] powerpc 2.6.21-rt1: add a need_resched_delayed() check Tsutomu OWA
2007-05-14  6:30 ` [patch 0/4] powerpc 2.6.21-rt1: reduce scheduling latency by changing tlb flush size Tsutomu OWA
2007-05-14  6:38   ` [patch 4/4] " Tsutomu OWA
2007-05-14  6:51     ` Thomas Gleixner
2007-05-14  6:51       ` Thomas Gleixner
2007-05-14  7:28       ` Tsutomu OWA
2007-05-14  7:28         ` Tsutomu OWA
2007-05-14 14:40         ` Arnd Bergmann
2007-05-14 14:40           ` Arnd Bergmann
2007-05-15  4:12           ` Tsutomu OWA
2007-05-15  4:12             ` Tsutomu OWA
2007-05-15  7:34             ` Benjamin Herrenschmidt
2007-05-15  7:34               ` Benjamin Herrenschmidt
2007-05-15  6:27           ` Tsutomu OWA
2007-05-15  7:38             ` Benjamin Herrenschmidt [this message]
2007-05-15  7:38               ` Benjamin Herrenschmidt
2007-05-15  8:08               ` Tsutomu OWA
2007-05-15  8:08                 ` Tsutomu OWA
2007-05-15  8:40                 ` Benjamin Herrenschmidt
2007-05-15  8:40                   ` Benjamin Herrenschmidt
2007-05-15  7:23           ` Benjamin Herrenschmidt

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