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Commit c7a3589e authored by Mike Travis's avatar Mike Travis Committed by Ingo Molnar
Browse files

Xen: reduce memory required for cpu_evtchn_mask 



Impact: reduce memory usage.

Reduce this significant gain in the amount of memory used
when NR_CPUS bumped from 128 to 4096 by allocating the
array based on nr_cpu_ids:

    65536  +2031616   2097152 +3100%  cpu_evtchn_mask(.bss)

Signed-off-by: default avatarMike Travis <travis@sgi.com>
Cc: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Chris Wright <chrisw@sous-sol.org>
Cc: virtualization@lists.osdl.org
Cc: xen-devel@lists.xensource.com
parent d38b223c

drivers/xen/events.c

+16 −5
Original line number Diff line number Diff line
@@ -75,7 +75,14 @@ enum { 
static int evtchn_to_irq[NR_EVENT_CHANNELS] = {

	[0 ... NR_EVENT_CHANNELS-1] = -1

};

static unsigned long cpu_evtchn_mask[NR_CPUS][NR_EVENT_CHANNELS/BITS_PER_LONG];

struct cpu_evtchn_s {

	unsigned long bits[NR_EVENT_CHANNELS/BITS_PER_LONG];

};

static struct cpu_evtchn_s *cpu_evtchn_mask_p;

static inline unsigned long *cpu_evtchn_mask(int cpu)

{

	return cpu_evtchn_mask_p[cpu].bits;

}

static u8 cpu_evtchn[NR_EVENT_CHANNELS];



/* Reference counts for bindings to IRQs. */
@@ -115,7 +122,7 @@ static inline unsigned long active_evtchns(unsigned int cpu, 
					   unsigned int idx)

{

	return (sh->evtchn_pending[idx] &

		cpu_evtchn_mask[cpu][idx] &

		cpu_evtchn_mask(cpu)[idx] &

		~sh->evtchn_mask[idx]);

}
@@ -128,8 +135,8 @@ static void bind_evtchn_to_cpu(unsigned int chn, unsigned int cpu) 
	cpumask_copy(irq_to_desc(irq)->affinity, cpumask_of(cpu));

#endif



	__clear_bit(chn, cpu_evtchn_mask[cpu_evtchn[chn]]);

	__set_bit(chn, cpu_evtchn_mask[cpu]);

	__clear_bit(chn, cpu_evtchn_mask(cpu_evtchn[chn]));

	__set_bit(chn, cpu_evtchn_mask(cpu));



	cpu_evtchn[chn] = cpu;

}
@@ -147,7 +154,7 @@ static void init_evtchn_cpu_bindings(void) 
#endif



	memset(cpu_evtchn, 0, sizeof(cpu_evtchn));

	memset(cpu_evtchn_mask[0], ~0, sizeof(cpu_evtchn_mask[0]));

	memset(cpu_evtchn_mask(0), ~0, sizeof(cpu_evtchn_mask(0)));

}



static inline unsigned int cpu_from_evtchn(unsigned int evtchn)
@@ -822,6 +829,10 @@ static struct irq_chip xen_dynamic_chip __read_mostly = { 
void __init xen_init_IRQ(void)

{

	int i;

	size_t size = nr_cpu_ids * sizeof(struct cpu_evtchn_s);



	cpu_evtchn_mask_p = kmalloc(size, GFP_KERNEL);

	BUG_ON(cpu_evtchn_mask == NULL);



	init_evtchn_cpu_bindings();