linux-kernel - Re: [PATCH] x86: Distinguish TLB shootdown interrupts from other functions call interrupts

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Message-ID: <20120920085033.14512.98190.stgit@hpxw>
Date:	Thu, 20 Sep 2012 17:50:33 +0900
From:	Tomoki Sekiyama <tomoki.sekiyama.qu@...achi.com>
To:	x86@...nel.org
Cc:	Alex Shi <alex.shi@...el.com>, yrl.pp-manager.tt@...achi.com,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] x86: Distinguish TLB shootdown interrupts from other
 functions call interrupts

Hi Alex,

thank you for the review.

>>     sum += irq_stats(cpu)->irq_call_count;
>> -   sum += irq_stats(cpu)->irq_tlb_count;
>> +   /* irq_tlb_count is already added to irq_call_count */
>
>redundant comments here?

>> @@ -98,6 +98,9 @@ static void flush_tlb_func(void *info)
>>  {
>>	struct flush_tlb_info *f = info;
>>
>> +	/* irq_call_cnt is also incremented; be subtracted on display */
>
>If is it better to move above explanation to irq_call_cnt definition place: harirq.h?

Agreed.

In the patch below, I reduced the redundant comments.

--
As TLB shootdown requests to other CPU cores are now using function call
interrupts, TLB shootdowns entry in /proc/interrupts is always shown as 0.

This behavior change was introduced by commit 52aec3308db8 ("x86/tlb:
replace INVALIDATE_TLB_VECTOR by CALL_FUNCTION_VECTOR").

This patch reverts TLB shootdowns entry in /proc/interrupts to count TLB
shootdowns separately from the other function call interrupts.

Signed-off-by: Tomoki Sekiyama <tomoki.sekiyama.qu@...achi.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: Alex Shi <alex.shi@...el.com>
---
 arch/x86/include/asm/hardirq.h |    2 ++
 arch/x86/kernel/irq.c          |    4 ++--
 arch/x86/mm/tlb.c              |    2 ++
 3 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/hardirq.h b/arch/x86/include/asm/hardirq.h
index d3895db..e34b252 100644
--- a/arch/x86/include/asm/hardirq.h
+++ b/arch/x86/include/asm/hardirq.h
@@ -18,6 +18,8 @@ typedef struct {
 #ifdef CONFIG_SMP
 	unsigned int irq_resched_count;
 	unsigned int irq_call_count;
+	/* irq_tlb_count is double-counted in irq_call_count, so it must be
+	   subtracted from irq_call_count when displaying irq_call_count */
 	unsigned int irq_tlb_count;
 #endif
 #ifdef CONFIG_X86_THERMAL_VECTOR
diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
index d44f782..e4595f1 100644
--- a/arch/x86/kernel/irq.c
+++ b/arch/x86/kernel/irq.c
@@ -92,7 +92,8 @@ int arch_show_interrupts(struct seq_file *p, int prec)
 	seq_printf(p, "  Rescheduling interrupts\n");
 	seq_printf(p, "%*s: ", prec, "CAL");
 	for_each_online_cpu(j)
-		seq_printf(p, "%10u ", irq_stats(j)->irq_call_count);
+		seq_printf(p, "%10u ", irq_stats(j)->irq_call_count -
+					irq_stats(j)->irq_tlb_count);
 	seq_printf(p, "  Function call interrupts\n");
 	seq_printf(p, "%*s: ", prec, "TLB");
 	for_each_online_cpu(j)
@@ -147,7 +148,6 @@ u64 arch_irq_stat_cpu(unsigned int cpu)
 #ifdef CONFIG_SMP
 	sum += irq_stats(cpu)->irq_resched_count;
 	sum += irq_stats(cpu)->irq_call_count;
-	sum += irq_stats(cpu)->irq_tlb_count;
 #endif
 #ifdef CONFIG_X86_THERMAL_VECTOR
 	sum += irq_stats(cpu)->irq_thermal_count;
diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 613cd83..2d6d8ed 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -98,6 +98,8 @@ static void flush_tlb_func(void *info)
 {
 	struct flush_tlb_info *f = info;
 
+	inc_irq_stat(irq_tlb_count);
+
 	if (f->flush_mm != this_cpu_read(cpu_tlbstate.active_mm))
 		return;
 

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