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SubjectLimited RAM - how to save it?
Hi!

I'm working on a 4MB linux system (for a customer) which has quite
limited resources at all:

- 4MB RAM
- 386 or 486 like processor (9..16 BogoMIPS)
- < 100MB HDD
- Quite a lot user space running:-(

For me, 4MB seems to be a problem. I've stripped diwn the applications
quite a lot, but 4MB behaves very slow and unresponsible. Adding only
one more MB solves any performance problem! I've made a small patch
practically removing printk() from kernel which helps a lot (patch
attached below). Basically, the running kernel is ~160KB smaller!
Are there further methods of saving space? I've already done some
other things, but these don't help that much:

- A maximum of 64 concurrent processes
- Only 32 PTYs

If you've got further ideas on getting the kernel a bit smaller,
would be nice to get a mail dropped...

MfG, JBG


diff -Nur linux-2.2.19/Documentation/Configure.help linux-CUSTOM-2.2.19/Documentation/Configure.help
--- linux-2.2.19/Documentation/Configure.help Sun Mar 25 18:37:29 2001
+++ linux-CUSTOM-2.2.19/Documentation/Configure.help Mon Nov 5 11:30:47 2001
@@ -4942,6 +4942,14 @@
important data. This is primarily of use to people trying to debug
the middle and upper layers of the SCSI subsystem. If unsure, say N.

+Smaller kernel by omitting most messages
+CONFIG_NO_PRINTK
+ Enabling this option will result in a smaller kernel by removing
+ most text strings. This is only useful for emdedded systems where
+ you've got to live with <= 4MB of RAM. I386-only for now...
+
+ If unsure, say no.
+
Fibre Channel support
CONFIG_FC4
This is an experimental support for storage arrays connected to
diff -Nur linux-2.2.19/arch/i386/config.in linux-CUSTOM-2.2.19/arch/i386/config.in
--- linux-2.2.19/arch/i386/config.in Sun Mar 25 18:37:29 2001
+++ linux-CUSTOM-2.2.19/arch/i386/config.in Mon Nov 5 11:01:28 2001
@@ -210,5 +221,6 @@

#bool 'Debug kmalloc/kfree' CONFIG_DEBUG_MALLOC
bool 'Magic SysRq key' CONFIG_MAGIC_SYSRQ
+bool 'Eleminate *most* printk()s' CONFIG_NO_PRINTK
endmenu

diff -Nur linux-2.2.19/arch/i386/kernel/head.S linux-CUSTOM-2.2.19/arch/i386/kernel/head.S
--- linux-2.2.19/arch/i386/kernel/head.S Sun Mar 25 18:31:45 2001
+++ linux-CUSTOM-2.2.19/arch/i386/kernel/head.S Fri Nov 2 11:21:42 2001
@@ -315,7 +315,7 @@
movl %ax,%ds
movl %ax,%es
pushl $int_msg
- call SYMBOL_NAME(printk)
+ call SYMBOL_NAME(real_printk)
popl %eax
popl %ds
popl %es
diff -Nur linux-2.2.19/arch/i386/kernel/traps.c linux-CUSTOM-2.2.19/arch/i386/kernel/traps.c
--- linux-2.2.19/arch/i386/kernel/traps.c Sun Mar 25 18:37:30 2001
+++ linux-CUSTOM-2.2.19/arch/i386/kernel/traps.c Fri Nov 2 11:53:32 2001
@@ -135,16 +135,16 @@
esp = regs->esp;
ss = regs->xss & 0xffff;
}
- printk("CPU: %d\nEIP: %04x:[<%08lx>]\nEFLAGS: %08lx\n",
+ oops_printk("CPU: %d\nEIP: %04x:[<%08lx>]\nEFLAGS: %08lx\n",
smp_processor_id(), 0xffff & regs->xcs, regs->eip, regs->eflags);
- printk("eax: %08lx ebx: %08lx ecx: %08lx edx: %08lx\n",
+ oops_printk("eax: %08lx ebx: %08lx ecx: %08lx edx: %08lx\n",
regs->eax, regs->ebx, regs->ecx, regs->edx);
- printk("esi: %08lx edi: %08lx ebp: %08lx esp: %08lx\n",
+ oops_printk("esi: %08lx edi: %08lx ebp: %08lx esp: %08lx\n",
regs->esi, regs->edi, regs->ebp, esp);
- printk("ds: %04x es: %04x ss: %04x\n",
+ oops_printk("ds: %04x es: %04x ss: %04x\n",
regs->xds & 0xffff, regs->xes & 0xffff, ss);
store_TR(i);
- printk("Process %s (pid: %d, process nr: %d, stackpage=%08lx)",
+ oops_printk("Process %s (pid: %d, process nr: %d, stackpage=%08lx)",
current->comm, current->pid, 0xffff & i, 4096+(unsigned long)current);

/*
@@ -152,18 +152,18 @@
* time of the fault..
*/
if (in_kernel) {
- printk("\nStack: ");
+ oops_printk("\nStack: ");
stack = (unsigned long *) esp;
for(i=0; i < kstack_depth_to_print; i++) {
if (((long) stack & 8191) == 0)
break;
if (i && ((i % 8) == 0))
- printk("\n ");
- printk("%08lx ", *stack++);
+ oops_printk("\n ");
+ oops_printk("%08lx ", *stack++);
}
- printk("\nCall Trace: ");
+ oops_printk("\nCall Trace: ");
if (!esp || (esp & 3))
- printk("Bad ESP value.");
+ oops_printk("Bad ESP value.");
else {
stack = (unsigned long *) esp;
i = 1;
@@ -184,21 +184,21 @@
(addr <= (unsigned long) &_etext)) ||
((addr >= module_start) && (addr <= module_end))) {
if (i && ((i % 8) == 0))
- printk("\n ");
- printk("[<%08lx>] ", addr);
+ oops_printk("\n ");
+ oops_printk("[<%08lx>] ", addr);
i++;
}
}
}
- printk("\nCode: ");
+ oops_printk("\nCode: ");
if (!regs->eip || regs->eip==-1)
- printk("Bad EIP value.");
+ oops_printk("Bad EIP value.");
else {
for(i=0;i<20;i++)
- printk("%02x ", ((unsigned char *)regs->eip)[i]);
+ oops_printk("%02x ", ((unsigned char *)regs->eip)[i]);
}
}
- printk("\n");
+ oops_printk("\n");
}

spinlock_t die_lock;
@@ -207,7 +207,7 @@
{
console_verbose();
spin_lock_irq(&die_lock);
- printk("%s: %04lx\n", str, err & 0xffff);
+ oops_printk("%s: %04lx\n", str, err & 0xffff);
show_registers(regs);
spin_unlock_irq(&die_lock);
do_exit(SIGSEGV);
diff -Nur linux-2.2.19/include/linux/kernel.h linux-CUSTOM-2.2.19/include/linux/kernel.h
--- linux-2.2.19/include/linux/kernel.h Sun Mar 25 18:31:03 2001
+++ linux-CUSTOM-2.2.19/include/linux/kernel.h Mon Nov 5 12:19:04 2001
@@ -9,6 +9,7 @@

#include <stdarg.h>
#include <linux/linkage.h>
+#include <linux/config.h>

/* Optimization barrier */
/* The "volatile" is due to gcc bugs */
@@ -54,8 +55,16 @@

extern int session_of_pgrp(int pgrp);

-asmlinkage int printk(const char * fmt, ...)
+asmlinkage int real_printk(const char * fmt, ...)
__attribute__ ((format (printf, 1, 2)));
+
+#ifdef CONFIG_NO_PRINTK
+# define printk(format, arg...) do {} while(0)
+#else
+# define printk(format, arg...) real_printk(format, ## arg)
+#endif /* CONFIG_NO_PRINTK */
+
+#define oops_printk(format, arg...) real_printk(format, ## arg)

#if DEBUG
#define pr_debug(fmt,arg...) \
diff -Nur linux-2.2.19/kernel/ksyms.c linux-CUSTOM-2.2.19/kernel/ksyms.c
--- linux-2.2.19/kernel/ksyms.c Sun Mar 25 18:31:02 2001
+++ linux-CUSTOM-2.2.19/kernel/ksyms.c Fri Nov 2 11:07:04 2001
@@ -357,7 +357,7 @@

/* misc */
EXPORT_SYMBOL(panic);
-EXPORT_SYMBOL(printk);
+EXPORT_SYMBOL(real_printk);
EXPORT_SYMBOL(sprintf);
EXPORT_SYMBOL(vsprintf);
EXPORT_SYMBOL(kdevname);
diff -Nur linux-2.2.19/kernel/printk.c linux-CUSTOM-2.2.19/kernel/printk.c
--- linux-2.2.19/kernel/printk.c Sun Mar 25 18:31:02 2001
+++ linux-CUSTOM-2.2.19/kernel/printk.c Fri Nov 2 11:01:21 2001
@@ -249,7 +249,7 @@
return do_syslog(type, buf, len);
}

-asmlinkage int printk(const char *fmt, ...)
+asmlinkage int real_printk(const char *fmt, ...)
{
va_list args;
int i;
-
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