linux-kernel - [RFC 3/6] softirq: Add reverse group-to-softirq map

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Message-Id: <20180118161238.13792-4-dima@arista.com>
Date:   Thu, 18 Jan 2018 16:12:35 +0000
From:   Dmitry Safonov <dima@...sta.com>
To:     linux-kernel@...r.kernel.org
Cc:     Dmitry Safonov <dima@...sta.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Miller <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Hannes Frederic Sowa <hannes@...essinduktion.org>,
        Ingo Molnar <mingo@...nel.org>,
        "Levin, Alexander (Sasha Levin)" <alexander.levin@...izon.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Mauro Carvalho Chehab <mchehab@...pensource.com>,
        Mike Galbraith <efault@....de>,
        Paolo Abeni <pabeni@...hat.com>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Radu Rendec <rrendec@...sta.com>,
        Rik van Riel <riel@...hat.com>,
        Stanislaw Gruszka <sgruszka@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Wanpeng Li <wanpeng.li@...mail.com>
Subject: [RFC 3/6] softirq: Add reverse group-to-softirq map

For faster operation with pending mask:
pending &= group_to_softirq[group_nr];

Signed-off-by: Dmitry Safonov <dima@...sta.com>
---
 kernel/softirq.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/kernel/softirq.c b/kernel/softirq.c
index ca8c3db4570d..7de5791c08f9 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -54,6 +54,7 @@ EXPORT_SYMBOL(irq_stat);
 #endif
 
 static struct softirq_action softirq_vec[NR_SOFTIRQS] __cacheline_aligned_in_smp;
+static unsigned group_to_softirqs[sizeof(softirq_vec[0].group_mask)] __cacheline_aligned_in_smp;
 static unsigned __initdata nr_softirq_groups = 0;
 
 DEFINE_PER_CPU(struct task_struct *, ksoftirqd);
@@ -650,11 +651,28 @@ static void __init setup_default_softirq_group(unsigned nr)
 	}
 }
 
+static void __init fill_group_to_softirq_maps(void)
+{
+	unsigned i;
+
+	for (i = 0; i < NR_SOFTIRQS; i++) {
+		u32 mask = softirq_vec[i].group_mask;
+		unsigned j, group = 0;
+
+		while ((j = ffs(mask))) {
+			group += j - 1;
+			group_to_softirqs[group] |= (1 << i);
+			mask >>= j;
+		}
+	}
+}
+
 void __init softirq_init(void)
 {
 	int cpu;
 
 	setup_default_softirq_group(nr_softirq_groups++);
+	fill_group_to_softirq_maps();
 
 	for_each_possible_cpu(cpu) {
 		per_cpu(tasklet_vec, cpu).tail =
-- 
2.13.6