Commit-ID: 7064d865af804b9b841e7b9a3e9b653e40c3e5ca Gitweb: http://git.kernel.org/tip/7064d865af804b9b841e7b9a3e9b653e40c3e5ca Author: Shaohua Li <shaohua.li@xxxxxxxxx> AuthorDate: Mon, 17 Jan 2011 10:52:10 +0800 Committer: Ingo Molnar <mingo@xxxxxxx> CommitDate: Mon, 14 Feb 2011 13:03:08 +0100 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: Shaohua Li <shaohua.li@xxxxxxxxx> Acked-by: Eric Dumazet <eric.dumazet@xxxxxxxxx> Cc: Andi Kleen <andi@xxxxxxxxxxxxxx> LKML-Reference: <1295232730.1949.710.camel@sli10-conroe> Signed-off-by: Ingo Molnar <mingo@xxxxxxx> --- arch/x86/mm/tlb.c | 11 ++++------- 1 files changed, 4 insertions(+), 7 deletions(-) diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c index 6acc724..55272d7 100644 --- a/arch/x86/mm/tlb.c +++ b/arch/x86/mm/tlb.c @@ -179,12 +179,8 @@ 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. - */ - raw_spin_lock(&f->tlbstate_lock); + if (nr_cpu_ids > NUM_INVALIDATE_TLB_VECTORS) + raw_spin_lock(&f->tlbstate_lock); f->flush_mm = mm; f->flush_va = va; @@ -202,7 +198,8 @@ static void flush_tlb_others_ipi(const struct cpumask *cpumask, f->flush_mm = NULL; f->flush_va = 0; - raw_spin_unlock(&f->tlbstate_lock); + if (nr_cpu_ids > NUM_INVALIDATE_TLB_VECTORS) + raw_spin_unlock(&f->tlbstate_lock); } void native_flush_tlb_others(const struct cpumask *cpumask, -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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