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powerpc: Reduce footprint of xics_ipi_struct

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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 <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Anton Blanchard 2010-01-31 20:32:51 +00:00 committed by Benjamin Herrenschmidt
parent 8c007bfdf1
commit fda9d86100
1 changed files with 11 additions and 15 deletions
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26
arch/powerpc/platforms/pseries/xics.c
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@ -510,15 +510,13 @@ 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);
@ -544,25 +542,23 @@ void smp_xics_message_pass(int target, int msg)
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