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Commit fda9d861 authored by Anton Blanchard's avatar Anton Blanchard Committed by Benjamin Herrenschmidt
Browse files

powerpc: Reduce footprint of xics_ipi_struct 



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: default avatarAnton Blanchard <anton@samba.org>
Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
parent 8c007bfd

arch/powerpc/platforms/pseries/xics.c

+11 −15
Original line number Diff line number Diff line
@@ -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