From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 38A3BC43142 for ; Fri, 22 Jun 2018 17:23:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EC5CB23D08 for ; Fri, 22 Jun 2018 17:23:42 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EC5CB23D08 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934192AbeFVRXk (ORCPT ); Fri, 22 Jun 2018 13:23:40 -0400 Received: from mga01.intel.com ([192.55.52.88]:32270 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932721AbeFVRXg (ORCPT ); Fri, 22 Jun 2018 13:23:36 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga101.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 22 Jun 2018 10:23:35 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.51,258,1526367600"; d="scan'208";a="66857334" Received: from asotoma-mobl1.amr.corp.intel.com (HELO [10.7.201.147]) ([10.7.201.147]) by orsmga001.jf.intel.com with ESMTP; 22 Jun 2018 10:23:26 -0700 Subject: Re: [PATCH 5/7] x86,tlb: only send page table free TLB flush to lazy TLB CPUs To: Rik van Riel , linux-kernel@vger.kernel.org References: <20180620195652.27251-1-riel@surriel.com> <20180620195652.27251-6-riel@surriel.com> Cc: 86@vger.kernel.org, luto@kernel.org, mingo@kernel.org, tglx@linutronix.de, efault@gmx.de, songliubraving@fb.com, kernel-team@fb.com From: Dave Hansen Openpgp: preference=signencrypt Autocrypt: addr=dave.hansen@linux.intel.com; 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Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 MIME-Version: 1.0 In-Reply-To: <20180620195652.27251-6-riel@surriel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/20/2018 12:56 PM, Rik van Riel wrote: > CPUs in TLBSTATE_OK have either received TLB flush IPIs earlier on during > the munmap (when the user memory was unmapped), or have context switched > and reloaded during that stage of the munmap. > > Page table free TLB flushes only need to be sent to CPUs in lazy TLB > mode, which TLB contents might not yet be up to date yet. > > Signed-off-by: Rik van Riel > Tested-by: Song Liu > --- > arch/x86/mm/tlb.c | 26 +++++++++++++++++++++++--- > 1 file changed, 23 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c > index 4b27d8469848..40b00055c883 100644 > --- a/arch/x86/mm/tlb.c > +++ b/arch/x86/mm/tlb.c > @@ -752,11 +752,31 @@ void tlb_flush_remove_tables_local(void *arg) > void tlb_flush_remove_tables(struct mm_struct *mm) > { > int cpu = get_cpu(); > + cpumask_var_t varmask; > + > + if (cpumask_any_but(mm_cpumask(mm), cpu) >= nr_cpu_ids) > + return; Oh, man, we need a wrapper for that little nugget. I was really scratching my head about what this was doing until I saw the cpumask_any_but() comment: * Returns >= nr_cpu_ids if no cpus set. > + if (!zalloc_cpumask_var(&varmask, GFP_ATOMIC)) { > + /* Flush the TLB on all CPUs that have this mm loaded. */ > + smp_call_function_many(mm_cpumask(mm), tlb_flush_remove_tables_local, (void *)mm, 1); > + } Maybe: /* * If the cpumask allocation fails, do a brute-force * flush on all CPUs that have this mm loaded. */ Also, don't you need a return inside the if(){} block here? > /* > - * XXX: this really only needs to be called for CPUs in lazy TLB mode. > + * CPUs in TLBSTATE_OK either received a TLB flush IPI while the user > + * pages in this address range were unmapped, or have context switched > + * and reloaded %CR3 since then. > + * > + * Shootdown IPIs at page table freeing time only need to be sent to > + * CPUs that may have out of date TLB contents. > */ > - if (cpumask_any_but(mm_cpumask(mm), cpu) < nr_cpu_ids) > - smp_call_function_many(mm_cpumask(mm), tlb_flush_remove_tables_local, (void *)mm, 1); > + for_each_cpu(cpu, mm_cpumask(mm)) { > + if (per_cpu(cpu_tlbstate.state, cpu) != TLBSTATE_OK) > + cpumask_set_cpu(cpu, varmask); > + } > + > + smp_call_function_many(varmask, tlb_flush_remove_tables_local, (void *)mm, 1); > + free_cpumask_var(varmask); > } Would this look any better if you wrapped the mask manipulation in a: void mm_fill_lazy_tlb_cpu_mask(struct mm_struct *mm, cpumask_var_t *varmask) helper, including the explanation comments? cpumask_var_t lazy_cpus; ... cpumask allocation/fallback here mm_fill_lazy_tlb_cpu_mask(mm, &lazy_cpus); smp_call_function_many(lazy_cpus, tlb_flush_remove_...