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Message-ID: <7a8ad02f-63a8-c1aa-fdd1-39d973593d02@kaod.org>
Date: Sat, 15 May 2021 19:01:20 +0200
From: Cédric Le Goater <clg@...d.org>
To: Thomas Gleixner <tglx@...utronix.de>,
Nicholas Piggin <npiggin@...il.com>
CC: <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] genirq: reduce irqdebug bouncing cachelines
On 4/13/21 10:24 PM, Thomas Gleixner wrote:
> On Tue, Apr 13 2021 at 14:16, Cédric Le Goater wrote:
>>>> We could test irq_settings_no_debug() directly under handle_nested_irq()
>>>> and handle_irq_event_percpu() to avoid calling note_interrupt(), just
>>>> like we do for noirqdebug.
>>>
>>> We can do that, but then we should not just make it:
>>>
>>> if (!irqnodebug && !irq_settings_no_debug(desc))
>>> note_interrupt(...);
>>>
>>> Instead have only one condition:
>>>
>>> if (!irq_settings_no_debug(desc))
>>> note_interrupt(...);
>>>
>>> See the uncompiled delta patch below.
>>
>> I merged this second part with the first and gave IRQF_NO_DEBUG a try
>> on P8 and P9 systems and all looked fine. I should send both patches
>> after IRQF_NO_AUTOEN is merged in mainline.
>
> Does having that NODEBUG flag set on the IPI irqs make a measurable
> difference or is it just too small to matter?
Here are some ipistorm results on a P10 system with 12 activated chips,
each with ~120 HW threads. The kernel is a 5.12 plus extras :
- XIVE IPI IRQ domain patchset (merged in 5.13-rc1)
- MSI IRQ domain pachset (should not have any impact)
- your IRQF_NO_DEBUG patch.
There is some slight improvement on the first 4 chips but it gets
better when we reach the fifth which requires an extra hop on the
bus. On 12 chips, we are close to an extra 9%.
Given these results, I think it would good to have the IRQF_NO_DEBUG
flag.
Thanks,
C.
[*] https://github.com/antonblanchard/ipistorm
Mint/s
chips cpus IRQF_NO_DEBUG
---------------------------------------
0 15 4.32 4.32
31 8.63 8.65
47 12.86 12.89
63 17.11 17.16
79 21.29 21.40
95 25.45 25.67
111 29.61 29.80
1 127 33.53 33.64
143 37.55 37.77
159 41.50 41.78
175 45.42 45.63
191 49.39 49.51
207 53.27 53.61
223 57.17 57.73
239 61.05 61.59
2 255 64.94 65.69
271 65.20 62.62
287 62.20 65.18
303 63.96 67.69
319 65.74 69.95
335 67.45 71.84
351 69.63 72.75
3 367 70.96 74.38
383 72.34 75.62
399 74.26 77.69
415 76.49 79.78
431 78.46 81.67
447 79.87 82.50
463 82.07 85.13
479 83.95 87.03
4 495 87.67 92.94
511 93.70 98.74
527 95.43 101.45
543 97.39 103.39
559 98.95 104.76
575 100.08 105.70
591 101.26 107.06
607 102.17 108.16
5 623 103.27 109.44
639 104.95 111.14
655 106.59 112.36
671 107.92 113.72
687 108.75 115.25
703 109.84 117.06
719 110.99 118.45
6 735 112.30 119.07
751 114.19 120.72
767 115.59 122.70
783 116.69 124.80
799 118.62 126.38
815 120.38 128.36
831 120.78 129.15
847 122.69 130.44
7 863 123.65 132.44
879 124.78 133.83
895 126.58 135.43
911 128.02 136.85
927 130.48 138.98
943 130.98 140.58
959 132.17 141.74
8 975 134.55 142.62
991 134.89 143.82
1007 135.64 145.51
1023 137.23 147.22
1039 139.37 149.85
1055 141.80 150.27
1071 141.37 152.33
1087 143.08 153.20
9 1103 144.83 154.23
1119 144.55 155.96
1135 147.32 157.91
1151 148.31 159.04
1167 150.67 160.41
1183 149.44 161.82
1199 152.53 164.69
1215 153.51 165.31
10 1231 154.88 166.67
1247 156.06 168.40
1263 157.59 170.01
1279 158.74 172.10
1295 159.55 172.79
1311 160.74 173.62
1327 161.86 175.02
11 1343 163.75 175.95
1359 163.67 177.96
1375 164.95 178.94
1391 166.53 180.09
1407 167.17 181.25
1423 168.84 183.94
1439 170.20 183.96
1455 170.47 185.47
>From 130eb33a02eb9d98fd8d8148e420b7b7b243bb93 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@...utronix.de>
Date: Fri, 2 Apr 2021 08:23:25 +0200
Subject: [PATCH] genirq: Add a IRQF_NO_DEBUG flag
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
The whole call to note_interrupt() can be avoided or return early when
interrupts would be marked accordingly. For IPI handlers which always
return HANDLED the whole procedure is pretty pointless to begin with.
Add a IRQF_NO_DEBUG flag.
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Cédric Le Goater <clg@...d.org>
---
include/linux/interrupt.h | 3 +++
include/linux/irq.h | 2 ++
kernel/irq/settings.h | 12 ++++++++++++
kernel/irq/chip.c | 2 +-
kernel/irq/handle.c | 2 +-
kernel/irq/manage.c | 5 +++++
6 files changed, 24 insertions(+), 2 deletions(-)
diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index 4777850a6dc7..a52109c3f3a4 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -64,6 +64,8 @@
* IRQF_NO_AUTOEN - Don't enable IRQ or NMI automatically when users request it.
* Users will enable it explicitly by enable_irq() or enable_nmi()
* later.
+ * IRQF_NO_DEBUG - Exclude from runnaway detection for IPI and similar handlers,
+ * depends on IRQF_PERCPU.
*/
#define IRQF_SHARED 0x00000080
#define IRQF_PROBE_SHARED 0x00000100
@@ -78,6 +80,7 @@
#define IRQF_EARLY_RESUME 0x00020000
#define IRQF_COND_SUSPEND 0x00040000
#define IRQF_NO_AUTOEN 0x00080000
+#define IRQF_NO_DEBUG 0x00100000
#define IRQF_TIMER (__IRQF_TIMER | IRQF_NO_SUSPEND | IRQF_NO_THREAD)
diff --git a/include/linux/irq.h b/include/linux/irq.h
index 31b347c9f8dd..8e9a9ae471a6 100644
--- a/include/linux/irq.h
+++ b/include/linux/irq.h
@@ -72,6 +72,7 @@ enum irqchip_irq_state;
* mechanism and from core side polling.
* IRQ_DISABLE_UNLAZY - Disable lazy irq disable
* IRQ_HIDDEN - Don't show up in /proc/interrupts
+ * IRQ_NO_DEBUG - Exclude from note_interrupt() debugging
*/
enum {
IRQ_TYPE_NONE = 0x00000000,
@@ -99,6 +100,7 @@ enum {
IRQ_IS_POLLED = (1 << 18),
IRQ_DISABLE_UNLAZY = (1 << 19),
IRQ_HIDDEN = (1 << 20),
+ IRQ_NO_DEBUG = (1 << 21),
};
#define IRQF_MODIFY_MASK \
diff --git a/kernel/irq/settings.h b/kernel/irq/settings.h
index 403378b9947b..7b7efb1a114b 100644
--- a/kernel/irq/settings.h
+++ b/kernel/irq/settings.h
@@ -18,6 +18,7 @@ enum {
_IRQ_IS_POLLED = IRQ_IS_POLLED,
_IRQ_DISABLE_UNLAZY = IRQ_DISABLE_UNLAZY,
_IRQ_HIDDEN = IRQ_HIDDEN,
+ _IRQ_NO_DEBUG = IRQ_NO_DEBUG,
_IRQF_MODIFY_MASK = IRQF_MODIFY_MASK,
};
@@ -33,6 +34,7 @@ enum {
#define IRQ_IS_POLLED GOT_YOU_MORON
#define IRQ_DISABLE_UNLAZY GOT_YOU_MORON
#define IRQ_HIDDEN GOT_YOU_MORON
+#define IRQ_NO_DEBUG GOT_YOU_MORON
#undef IRQF_MODIFY_MASK
#define IRQF_MODIFY_MASK GOT_YOU_MORON
@@ -174,3 +176,13 @@ static inline bool irq_settings_is_hidden(struct irq_desc *desc)
{
return desc->status_use_accessors & _IRQ_HIDDEN;
}
+
+static inline void irq_settings_set_no_debug(struct irq_desc *desc)
+{
+ desc->status_use_accessors |= _IRQ_NO_DEBUG;
+}
+
+static inline bool irq_settings_no_debug(struct irq_desc *desc)
+{
+ return desc->status_use_accessors & _IRQ_NO_DEBUG;
+}
diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index 8cc8e5713287..7f04c7d8296e 100644
--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -481,7 +481,7 @@ void handle_nested_irq(unsigned int irq)
for_each_action_of_desc(desc, action)
action_ret |= action->thread_fn(action->irq, action->dev_id);
- if (!noirqdebug)
+ if (!irq_settings_no_debug(desc))
note_interrupt(desc, action_ret);
raw_spin_lock_irq(&desc->lock);
diff --git a/kernel/irq/handle.c b/kernel/irq/handle.c
index 762a928e18f9..221d80c31e94 100644
--- a/kernel/irq/handle.c
+++ b/kernel/irq/handle.c
@@ -197,7 +197,7 @@ irqreturn_t handle_irq_event_percpu(struct irq_desc *desc)
add_interrupt_randomness(desc->irq_data.irq, flags);
- if (!noirqdebug)
+ if (!irq_settings_no_debug(desc))
note_interrupt(desc, retval);
return retval;
}
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 4c14356543d9..7bdd09e7d5f0 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -1686,8 +1686,13 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
if (new->flags & IRQF_PERCPU) {
irqd_set(&desc->irq_data, IRQD_PER_CPU);
irq_settings_set_per_cpu(desc);
+ if (new->flags & IRQF_NO_DEBUG)
+ irq_settings_set_no_debug(desc);
}
+ if (noirqdebug)
+ irq_settings_set_no_debug(desc);
+
if (new->flags & IRQF_ONESHOT)
desc->istate |= IRQS_ONESHOT;
--
2.31.1
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