On Sat, 20 May 2000, Christopher Thompson wrote:
> I have now completed and tested my second TSC patch. It is available at:
> http://hypocrite.org/linux/tsc.patch.new.tar.gz
>
> This works with 2.3.99-pre8 at least, probably most others. This one disables
> use of the TSC by an option in the configuration (i.e. make config, make
> menuconfig, whatever) and therefore has NO performance impact on TSC-enabled
> kernels. The disadvantage is that this is another option to set in your
> configuration.
Hmm, a while ago I prepared a patch to disable TSC via a "notsc" kernel
command line option. I needed it to test SMP support for TSC-less
systems. While it makes the kernel larger by a few instructions, all of
them are located in the init section and are discarded after a bootup.
There is no runtime impact on the patch.
I believe this one might be useful for someone. It applies cleanly to
2.3.99-pre8.
--
+ Maciej W. Rozycki, Technical University of Gdansk, Poland +
+--------------------------------------------------------------+
+ e-mail: [EMAIL PROTECTED], PGP key available +
diff -u --recursive --new-file linux-2.3.99-pre6-2.macro/arch/i386/kernel/setup.c
linux-2.3.99-pre6-2/arch/i386/kernel/setup.c
--- linux-2.3.99-pre6-2.macro/arch/i386/kernel/setup.c Fri Apr 14 19:40:25 2000
+++ linux-2.3.99-pre6-2/arch/i386/kernel/setup.c Tue Apr 18 22:10:16 2000
@@ -1535,6 +1535,18 @@
return p - buffer;
}
+#ifndef CONFIG_X86_TSC
+static int tsc_disable = 0;
+
+static int __init tsc_setup(char *str)
+{
+ tsc_disable = 1;
+ return 1;
+}
+
+__setup("notsc", tsc_setup);
+#endif
+
int cpus_initialized = 0;
unsigned long cpu_initialized = 0;
@@ -1558,6 +1570,13 @@
if (cpu_has_vme || cpu_has_tsc || cpu_has_de)
clear_in_cr4(X86_CR4_VME|X86_CR4_PVI|X86_CR4_TSD|X86_CR4_DE);
+#ifndef CONFIG_X86_TSC
+ if (tsc_disable && cpu_has_tsc) {
+ printk("Disabling TSC...\n");
+ boot_cpu_data.x86_capability &= ~X86_FEATURE_TSC;
+ set_in_cr4(X86_CR4_TSD);
+ }
+#endif
__asm__ __volatile__("lgdt %0": "=m" (gdt_descr));
__asm__ __volatile__("lidt %0": "=m" (idt_descr));
diff -u --recursive --new-file linux-2.3.99-pre6-2.macro/init/main.c
linux-2.3.99-pre6-2/init/main.c
--- linux-2.3.99-pre6-2.macro/init/main.c Fri Apr 14 19:40:33 2000
+++ linux-2.3.99-pre6-2/init/main.c Tue Apr 18 09:01:58 2000
@@ -481,12 +481,12 @@
lock_kernel();
printk(linux_banner);
setup_arch(&command_line);
+ parse_options(command_line);
trap_init();
init_IRQ();
sched_init();
time_init();
softirq_init();
- parse_options(command_line);
/*
* HACK ALERT! This is early. We're enabling the console before
-
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