The patch aims to fix a performance issue for the syscall
personality(PER_LINUX32).
On IA-64 box, the syscall personality (PER_LINUX32) has poor performance
because it failed to find the Linux/x86 execution domain. Then it tried
to load the kernel module however it failed always and it used the
default
execution domain PER_LINUX instead. Requesting kernel modules is very
expensive. It caused the performance issue. (see the
function lookup_exec_domain in kernel/exec_domain.c).
To resolve the issue, execution domain Linux/x86 is always registered in
initialization time for IA-64 architecture.
Signed-off-by: Xiaolan Huang <xiaolan.huang@xxxxxxxxx>
diff -uprN -X linux-2.6.26-rc1/Documentation/dontdiff
linux-2.6.26-rc1/arch/ia64/ia32/ia32_support.c
linux-2.6.26-fix/arch/ia64/ia32/ia32_support.c
--- linux-2.6.26-rc1/arch/ia64/ia32/ia32_support.c 2008-05-04
02:59:44.000000000 +0800
+++ linux-2.6.26-fix/arch/ia64/ia32/ia32_support.c 2008-05-15
00:48:46.000000000 +0800
@@ -15,7 +15,6 @@
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/mm.h>
-#include <linux/personality.h>
#include <linux/sched.h>
#include <asm/intrinsics.h>
@@ -29,7 +28,6 @@
extern int die_if_kernel (char *str, struct pt_regs *regs, long err);
-struct exec_domain ia32_exec_domain;
struct page *ia32_shared_page[NR_CPUS];
unsigned long *ia32_boot_gdt;
unsigned long *cpu_gdt_table[NR_CPUS];
@@ -240,14 +238,6 @@ ia32_cpu_init (void)
static int __init
ia32_init (void)
{
- ia32_exec_domain.name = "Linux/x86";
- ia32_exec_domain.handler = NULL;
- ia32_exec_domain.pers_low = PER_LINUX32;
- ia32_exec_domain.pers_high = PER_LINUX32;
- ia32_exec_domain.signal_map = default_exec_domain.signal_map;
- ia32_exec_domain.signal_invmap =
default_exec_domain.signal_invmap;
- register_exec_domain(&ia32_exec_domain);
-
#if PAGE_SHIFT > IA32_PAGE_SHIFT
{
extern struct kmem_cache *ia64_partial_page_cachep;
diff -uprN -X linux-2.6.26-rc1/Documentation/dontdiff
linux-2.6.26-rc1/arch/ia64/mm/init.c
linux-2.6.26-fix/arch/ia64/mm/init.c
--- linux-2.6.26-rc1/arch/ia64/mm/init.c 2008-05-04
02:59:44.000000000 +0800
+++ linux-2.6.26-fix/arch/ia64/mm/init.c 2008-05-15
00:49:23.000000000 +0800
@@ -719,3 +719,28 @@ out:
EXPORT_SYMBOL_GPL(remove_memory);
#endif /* CONFIG_MEMORY_HOTREMOVE */
#endif
+
+/*
+ * Even when CONFIG_IA32_SUPPORT is not enabled it is
+ * useful to have the Linux/x86 domain registered to
+ * avoid an attempted module load when emulators call
+ * personality(PER_LINUX32). This saves several milliseconds
+ * on each such call.
+ */
+static struct exec_domain ia32_exec_domain;
+
+static int __init
+per_linux32_init(void)
+{
+ ia32_exec_domain.name = "Linux/x86";
+ ia32_exec_domain.handler = NULL;
+ ia32_exec_domain.pers_low = PER_LINUX32;
+ ia32_exec_domain.pers_high = PER_LINUX32;
+ ia32_exec_domain.signal_map = default_exec_domain.signal_map;
+ ia32_exec_domain.signal_invmap =
default_exec_domain.signal_invmap;
+ register_exec_domain(&ia32_exec_domain);
+
+ return 0;
+}
+
+__initcall(per_linux32_init);
Thanks
Xiaolan
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