Commit 7064d865 authored by Shaohua Li's avatar Shaohua Li Committed by Ingo Molnar

x86: Avoid tlbstate lock if not enough cpus

This one isn't related to previous patch. If online cpus are
below NUM_INVALIDATE_TLB_VECTORS, we don't need the lock. The
comments in the code declares we don't need the check, but a hot
lock still needs an atomic operation and expensive, so add the
check here.

Uses nr_cpu_ids here as suggested by Eric Dumazet.
Signed-off-by: default avatarShaohua Li <shaohua.li@intel.com>
Acked-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
Cc: Andi Kleen <andi@firstfloor.org>
LKML-Reference: <1295232730.1949.710.camel@sli10-conroe>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 70e4a369
......@@ -179,11 +179,7 @@ static void flush_tlb_others_ipi(const struct cpumask *cpumask,
sender = this_cpu_read(tlb_vector_offset);
f = &flush_state[sender];
/*
* Could avoid this lock when
* num_online_cpus() <= NUM_INVALIDATE_TLB_VECTORS, but it is
* probably not worth checking this for a cache-hot lock.
*/
if (nr_cpu_ids > NUM_INVALIDATE_TLB_VECTORS)
raw_spin_lock(&f->tlbstate_lock);
f->flush_mm = mm;
......@@ -202,6 +198,7 @@ static void flush_tlb_others_ipi(const struct cpumask *cpumask,
f->flush_mm = NULL;
f->flush_va = 0;
if (nr_cpu_ids > NUM_INVALIDATE_TLB_VECTORS)
raw_spin_unlock(&f->tlbstate_lock);
}
......
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