From: Mikael Pettersson <mikpe@csd.uu.se>
To: torvalds@transmeta.com
Cc: linux-kernel@vger.kernel.org
Subject: [PATCH] shrink check_nmi_watchdog stack frame
Date: Thu, 25 Jul 2002 18:06:55 +0200 (MET DST) [thread overview]
Message-ID: <200207251606.SAA19671@harpo.it.uu.se> (raw)
This patch for 2.5.28 reduces the stack frame size of
arch/i386/kernel/nmi.c:check_nmi_watchdog() from 4096 bytes
in the worst case to 128 bytes. Linus, please apply.
The problem with the current code is that it copies the entire
irq_stat[] array, when only a single field (__nmi_count) is of
interest. The irq_stat_t element type is only 28 bytes, but it
is also ____cacheline_aligned, and that blows the array up to
4096 bytes on SMP P4 Xeons, 2048 bytes on SMP K7s, and 1024 bytes
on SMP P5/P6s. The patch reduces this to NR_CPUS*4==128 bytes.
/Mikael
diff -ruN linux-2.5.28/arch/i386/kernel/nmi.c linux-2.5.28.check-nmi/arch/i386/kernel/nmi.c
--- linux-2.5.28/arch/i386/kernel/nmi.c Thu Jul 25 01:27:29 2002
+++ linux-2.5.28.check-nmi/arch/i386/kernel/nmi.c Thu Jul 25 01:31:55 2002
@@ -72,19 +72,20 @@
int __init check_nmi_watchdog (void)
{
- irq_cpustat_t tmp[NR_CPUS];
+ unsigned int prev_nmi_count[NR_CPUS];
int cpu;
printk(KERN_INFO "testing NMI watchdog ... ");
- memcpy(tmp, irq_stat, sizeof(tmp));
+ for (cpu = 0; cpu < NR_CPUS; cpu++)
+ prev_nmi_count[cpu] = irq_stat[cpu].__nmi_count;
local_irq_enable();
mdelay((10*1000)/nmi_hz); // wait 10 ticks
for (cpu = 0; cpu < NR_CPUS; cpu++) {
if (!cpu_online(cpu))
continue;
- if (nmi_count(cpu) - tmp[cpu].__nmi_count <= 5) {
+ if (nmi_count(cpu) - prev_nmi_count[cpu] <= 5) {
printk("CPU#%d: NMI appears to be stuck!\n", cpu);
return -1;
}
next reply other threads:[~2002-07-25 16:03 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-07-25 16:06 Mikael Pettersson [this message]
-- strict thread matches above, loose matches on Subject: below --
2002-06-16 11:41 [PATCH] shrink check_nmi_watchdog stack frame Mikael Pettersson
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