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Date: Tue, 15 May 2007 18:40:37 +1000 From: Benjamin Herrenschmidt <benh@...nel.crashing.org> To: Tsutomu OWA <tsutomu.owa@...hiba.co.jp> Cc: Arnd Bergmann <arnd@...db.de>, linuxppc-dev@...abs.org, Thomas Gleixner <tglx@...utronix.de>, mingo@...e.hu, linux-kernel@...r.kernel.org Subject: Re: [patch 4/4] powerpc 2.6.21-rt1: reduce scheduling latency by changing tlb flush size > > 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. > > Yes, here is the trace log. Accordint it, flushing 9 entries takes about 50us. > It means that flushing 192 (PPC64_TLB_BATCH_NR) entries takes 1ms. > Please note that tracing causes *roughly* 20-30% overhead, though. > > I'm afraid I don't have numbers w/ native version, but I suppose you have :) Actually I don't off hand but I'll try to get some. > # cat /proc/latency_trace > preemption latency trace v1.1.5 on 2.6.21-rt1 > -------------------------------------------------------------------- > latency: 60 us, #53/53, CPU#0 | (M:rt VP:0, KP:0, SP:1 HP:1 #P:1) > ----------------- > | task: inetd-358 (uid:0 nice:0 policy:0 rt_prio:0) > ----------------- > => started at: .__switch_to+0xa8/0x178 <c00000000000feec> > => ended at: .__start+0x4000000000000000/0x8 <00000000> > > _------=> CPU# > / _-----=> irqs-off > | / _----=> need-resched > || / _---=> hardirq/softirq > ||| / _--=> preempt-depth > |||| / > ||||| delay > cmd pid ||||| time | caller > \ / ||||| \ | / > inetd-358 0D..2 0us : .user_trace_start (.__switch_to) > inetd-358 0D..2 0us : .rt_up (.user_trace_start) > inetd-358 0D..3 1us : .rt_mutex_unlock (.rt_up) > inetd-358 0D..3 2us : .__flush_tlb_pending (.__switch_to) > inetd-358 0D..4 3us : .flush_hash_range (.__flush_tlb_pending) > inetd-358 0D..4 3us : .flush_hash_page (.flush_hash_range) > inetd-358 0D..4 4us : .beat_lpar_hpte_invalidate (.flush_hash_page) > inetd-358 0D..4 5us : .__spin_lock_irqsave (.beat_lpar_hpte_invalidate) > inetd-358 0D..5 6us+: .beat_lpar_hpte_getword0 (.beat_lpar_hpte_invalidate) > inetd-358 0D..5 13us : .__spin_unlock_irqrestore (.beat_lpar_hpte_invalidate) > inetd-358 0D..4 13us : .flush_hash_page (.flush_hash_range) > inetd-358 0D..4 14us : .beat_lpar_hpte_invalidate (.flush_hash_page) > inetd-358 0D..4 14us : .__spin_lock_irqsave (.beat_lpar_hpte_invalidate) > inetd-358 0D..5 15us+: .beat_lpar_hpte_getword0 (.beat_lpar_hpte_invalidate) > inetd-358 0D..5 18us : .__spin_unlock_irqrestore (.beat_lpar_hpte_invalidate) > inetd-358 0D..4 19us : .flush_hash_page (.flush_hash_range) > inetd-358 0D..4 20us : .beat_lpar_hpte_invalidate (.flush_hash_page) > inetd-358 0D..4 20us : .__spin_lock_irqsave (.beat_lpar_hpte_invalidate) > inetd-358 0D..5 21us+: .beat_lpar_hpte_getword0 (.beat_lpar_hpte_invalidate) > inetd-358 0D..5 24us : .__spin_unlock_irqrestore (.beat_lpar_hpte_invalidate) > inetd-358 0D..4 25us : .flush_hash_page (.flush_hash_range) > inetd-358 0D..4 25us : .beat_lpar_hpte_invalidate (.flush_hash_page) > inetd-358 0D..4 26us : .__spin_lock_irqsave (.beat_lpar_hpte_invalidate) > inetd-358 0D..5 26us+: .beat_lpar_hpte_getword0 (.beat_lpar_hpte_invalidate) > inetd-358 0D..5 30us : .__spin_unlock_irqrestore (.beat_lpar_hpte_invalidate) > inetd-358 0D..4 30us : .flush_hash_page (.flush_hash_range) > inetd-358 0D..4 31us : .beat_lpar_hpte_invalidate (.flush_hash_page) > inetd-358 0D..4 31us : .__spin_lock_irqsave (.beat_lpar_hpte_invalidate) > inetd-358 0D..5 32us+: .beat_lpar_hpte_getword0 (.beat_lpar_hpte_invalidate) > inetd-358 0D..5 36us : .__spin_unlock_irqrestore (.beat_lpar_hpte_invalidate) > inetd-358 0D..4 36us : .flush_hash_page (.flush_hash_range) > inetd-358 0D..4 37us : .beat_lpar_hpte_invalidate (.flush_hash_page) > inetd-358 0D..4 37us : .__spin_lock_irqsave (.beat_lpar_hpte_invalidate) > inetd-358 0D..5 38us+: .beat_lpar_hpte_getword0 (.beat_lpar_hpte_invalidate) > inetd-358 0D..5 41us : .__spin_unlock_irqrestore (.beat_lpar_hpte_invalidate) > inetd-358 0D..4 42us : .flush_hash_page (.flush_hash_range) > inetd-358 0D..4 42us : .beat_lpar_hpte_invalidate (.flush_hash_page) > inetd-358 0D..4 43us : .__spin_lock_irqsave (.beat_lpar_hpte_invalidate) > inetd-358 0D..5 43us+: .beat_lpar_hpte_getword0 (.beat_lpar_hpte_invalidate) > inetd-358 0D..5 47us : .__spin_unlock_irqrestore (.beat_lpar_hpte_invalidate) > inetd-358 0D..4 48us : .flush_hash_page (.flush_hash_range) > inetd-358 0D..4 48us : .beat_lpar_hpte_invalidate (.flush_hash_page) > inetd-358 0D..4 49us : .__spin_lock_irqsave (.beat_lpar_hpte_invalidate) > inetd-358 0D..5 49us+: .beat_lpar_hpte_getword0 (.beat_lpar_hpte_invalidate) > inetd-358 0D..5 52us : .__spin_unlock_irqrestore (.beat_lpar_hpte_invalidate) > inetd-358 0D..4 53us : .flush_hash_page (.flush_hash_range) > inetd-358 0D..4 54us : .beat_lpar_hpte_invalidate (.flush_hash_page) > inetd-358 0D..4 54us : .__spin_lock_irqsave (.beat_lpar_hpte_invalidate) > inetd-358 0D..5 55us+: .beat_lpar_hpte_getword0 (.beat_lpar_hpte_invalidate) > inetd-358 0D..5 58us : .__spin_unlock_irqrestore (.beat_lpar_hpte_invalidate) > inetd-358 0D..2 59us : .user_trace_stop (.__switch_to) > inetd-358 0D..2 60us : .user_trace_stop (.__switch_to) > -- owa - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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