From mboxrd@z Thu Jan 1 00:00:00 1970 From: Leonardo Bras Date: Thu, 06 Feb 2020 03:09:00 +0000 Subject: [PATCH v6 11/11] powerpc/mm/book3s64/pgtable: Uses counting method to skip serializing Message-Id: <20200206030900.147032-12-leonardo@linux.ibm.com> List-Id: References: <20200206030900.147032-1-leonardo@linux.ibm.com> In-Reply-To: <20200206030900.147032-1-leonardo@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , Arnd Bergmann , Andrew Morton , "Aneesh Kumar K.V" , Nicholas Piggin , Christophe Leroy , Steven Price , Robin Murphy , Leonardo Bras , Mahesh Salgaonkar , Balbir Singh , Reza Arbab , Thomas Gleixner , Allison Randal , Greg Kroah-Hartman , Mike Rapoport , Michal Suchanek Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, kvm-ppc@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org For each cpu in cpumask, checks if it's running a lockless pagetable walk. Then, run serialize_against_pte_lookup() only on these cpus. serialize_agains_pte_lookup() can take a long while when there are a lot of cpus in cpumask. This method is intended to reduce this waiting, while not impacting too much on the lockless pagetable walk. Signed-off-by: Leonardo Bras --- arch/powerpc/mm/book3s64/pgtable.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/mm/book3s64/pgtable.c b/arch/powerpc/mm/book3s64/pgtable.c index bb138b628f86..4822ff1aac4b 100644 --- a/arch/powerpc/mm/book3s64/pgtable.c +++ b/arch/powerpc/mm/book3s64/pgtable.c @@ -96,8 +96,22 @@ static DEFINE_PER_CPU(int, lockless_pgtbl_walk_counter); */ void serialize_against_pte_lookup(struct mm_struct *mm) { + int cpu; + struct cpumask cm; + smp_mb(); - smp_call_function_many(mm_cpumask(mm), do_nothing, NULL, 1); + + /* + * Fills a new cpumask only with cpus that are currently doing a + * lockless pagetable walk. This reduces time spent in this function. + */ + cpumask_clear(&cm); + for_each_cpu(cpu, mm_cpumask((mm))) { + if (per_cpu(lockless_pgtbl_walk_counter, cpu) > 0) + cpumask_set_cpu(cpu, &cm); + } + + smp_call_function_many(&cm, do_nothing, NULL, 1); } /* begin_lockless_pgtbl_walk: Must be inserted before a function call that does -- 2.24.1