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xen/multicall: special-case singleton hypercalls 

Singleton calls seem to end up being pretty common, so just
directly call the hypercall rather than going via multicall.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
This commit is contained in:
Jeremy Fitzhardinge 2010-12-17 17:32:28 -08:00
parent 4a7b005dbf
commit eac303bf2e
1 changed files with 22 additions and 5 deletions
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27
arch/x86/xen/multicalls.c
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@ -55,6 +55,7 @@ DEFINE_PER_CPU(unsigned long, xen_mc_irq_flags);
void xen_mc_flush(void)
{
struct mc_buffer *b = &__get_cpu_var(mc_buffer);
struct multicall_entry *mc;
int ret = 0;
unsigned long flags;
int i;
@ -67,7 +68,24 @@ void xen_mc_flush(void)
trace_xen_mc_flush(b->mcidx, b->argidx, b->cbidx);
if (b->mcidx) {
switch (b->mcidx) {
case 0:
/* no-op */
BUG_ON(b->argidx != 0);
break;
case 1:
/* Singleton multicall - bypass multicall machinery
and just do the call directly. */
mc = &b->entries[0];
mc->result = privcmd_call(mc->op,
mc->args[0], mc->args[1], mc->args[2],
mc->args[3], mc->args[4]);
ret = mc->result < 0;
break;
default:
#if MC_DEBUG
memcpy(b->debug, b->entries,
b->mcidx * sizeof(struct multicall_entry));
@ -94,11 +112,10 @@ void xen_mc_flush(void)
}
}
#endif
}
b->mcidx = 0;
b->argidx = 0;
} else
BUG_ON(b->argidx != 0);
b->mcidx = 0;
b->argidx = 0;
for (i = 0; i < b->cbidx; i++) {
struct callback *cb = &b->callbacks[i];