Right now we allocate a cacheline sized NR_CPUS array for xics IPI
communication. Use DECLARE_PER_CPU_SHARED_ALIGNED to put it in percpu
data in its own cacheline since it is written to by other cpus.
On a kernel with NR_CPUS=1024, this saves quite a lot of memory:
text data bss dec hex filename
8767779 2944260 1505724 13217763 c9afe3 vmlinux.irq_cpustat
8767555 2813444 1505724 13086723 c7b003 vmlinux.xics
A saving of around 128kB.
Signed-off-by: Anton Blanchard <an...@samba.org>
---
Index: linux-cpumask/arch/powerpc/platforms/pseries/xics.c
===================================================================
--- linux-cpumask.orig/arch/powerpc/platforms/pseries/xics.c 2010-02-01
17:28:56.980961887 +1100
+++ linux-cpumask/arch/powerpc/platforms/pseries/xics.c 2010-02-01
17:29:00.980963118 +1100
@@ -514,15 +514,13 @@ static void __init xics_init_host(void)
/*
* XICS only has a single IPI, so encode the messages per CPU
*/
-struct xics_ipi_struct {
- unsigned long value;
- } ____cacheline_aligned;
-
-static struct xics_ipi_struct xics_ipi_message[NR_CPUS] __cacheline_aligned;
+static DEFINE_PER_CPU_SHARED_ALIGNED(unsigned long, xics_ipi_message);
static inline void smp_xics_do_message(int cpu, int msg)
{
- set_bit(msg, &xics_ipi_message[cpu].value);
+ unsigned long *tgt = &per_cpu(xics_ipi_message, cpu);
+
+ set_bit(msg, tgt);
mb();
if (firmware_has_feature(FW_FEATURE_LPAR))
lpar_qirr_info(cpu, IPI_PRIORITY);
@@ -548,25 +546,23 @@ void smp_xics_message_pass(int target, i
static irqreturn_t xics_ipi_dispatch(int cpu)
{
+ unsigned long *tgt = &per_cpu(xics_ipi_message, cpu);
+
WARN_ON(cpu_is_offline(cpu));
mb(); /* order mmio clearing qirr */
- while (xics_ipi_message[cpu].value) {
- if (test_and_clear_bit(PPC_MSG_CALL_FUNCTION,
- &xics_ipi_message[cpu].value)) {
+ while (*tgt) {
+ if (test_and_clear_bit(PPC_MSG_CALL_FUNCTION, tgt)) {
smp_message_recv(PPC_MSG_CALL_FUNCTION);
}
- if (test_and_clear_bit(PPC_MSG_RESCHEDULE,
- &xics_ipi_message[cpu].value)) {
+ if (test_and_clear_bit(PPC_MSG_RESCHEDULE, tgt)) {
smp_message_recv(PPC_MSG_RESCHEDULE);
}
- if (test_and_clear_bit(PPC_MSG_CALL_FUNC_SINGLE,
- &xics_ipi_message[cpu].value)) {
+ if (test_and_clear_bit(PPC_MSG_CALL_FUNC_SINGLE, tgt)) {
smp_message_recv(PPC_MSG_CALL_FUNC_SINGLE);
}
#if defined(CONFIG_DEBUGGER) || defined(CONFIG_KEXEC)
- if (test_and_clear_bit(PPC_MSG_DEBUGGER_BREAK,
- &xics_ipi_message[cpu].value)) {
+ if (test_and_clear_bit(PPC_MSG_DEBUGGER_BREAK, tgt)) {
smp_message_recv(PPC_MSG_DEBUGGER_BREAK);
}
#endif
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