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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 92086C433EF for ; Fri, 8 Jul 2022 15:13:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238610AbiGHPNb (ORCPT ); Fri, 8 Jul 2022 11:13:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33962 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235427AbiGHPNa (ORCPT ); Fri, 8 Jul 2022 11:13:30 -0400 Received: from mga17.intel.com (mga17.intel.com [192.55.52.151]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 530E84F661 for ; Fri, 8 Jul 2022 08:13:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1657293205; x=1688829205; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=qigLlHz72omGc2V/B7goHZMXhuZ8SUNrG2eXAMYhtjo=; b=GgfIJ9xg4VvQo95BGQVKLb5AAuZ0dvjL2XHLdn/gd6ggUO7JwE4Mt6X5 c2fcZA8ZWyiBIYzNWMjmvoFsfo2VPYTDYu3K0pkndTXzYFB/zZv0QXJJ8 YZw1c7ZFzJRzHp/XWrVI/IV4RgwnTGYAlGuY+4trkA4QH0QzXQ4KfdfBh n3POnqwNtYDMpth+dlsboKby4SbaFs0JlXnc3BLXaGVNZIi81t8rv7edf W3MqUqqysBs0Z6fNyK76MqBAOehAfa0ZvoBXvSWhANkM+V1Pp3Pdc2XGQ aN4BkaLKgs17MDF4XKQo265qjqmywAQpPsbE5BqX/keU6wBtdaBAHxHJM g==; X-IronPort-AV: E=McAfee;i="6400,9594,10401"; a="264713688" X-IronPort-AV: E=Sophos;i="5.92,256,1650956400"; d="scan'208";a="264713688" Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 08 Jul 2022 08:13:24 -0700 X-IronPort-AV: E=Sophos;i="5.92,256,1650956400"; d="scan'208";a="626729479" Received: from yyan2-mobl2.amr.corp.intel.com (HELO [10.212.242.16]) ([10.212.242.16]) by orsmga001-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 08 Jul 2022 08:13:21 -0700 Message-ID: <283d7660-000a-81af-1d6b-4fdedcb6dfd8@intel.com> Date: Fri, 8 Jul 2022 08:13:13 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.9.1 Subject: Re: [PATCH] x86/mm/tlb: ignore f->new_tlb_gen when zero Content-Language: en-US To: David Hildenbrand , Nadav Amit , linux-kernel@vger.kernel.org, Hugh Dickins , Thomas Gleixner Cc: Ingo Molnar , Borislav Petkov , x86@kernel.org, Linux MM , Nadav Amit , Dave Hansen , Peter Zijlstra , Andy Lutomirski References: <20220708003053.158480-1-namit@vmware.com> From: Dave Hansen In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/8/22 04:40, David Hildenbrand wrote: >> diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c >> index d9314cc8b81f..d81b4084bb8a 100644 >> --- a/arch/x86/mm/tlb.c >> +++ b/arch/x86/mm/tlb.c >> @@ -771,14 +771,14 @@ static void flush_tlb_func(void *info) >> return; >> } >> >> - if (f->new_tlb_gen <= local_tlb_gen) { >> + if (unlikely(f->new_tlb_gen != 0 && f->new_tlb_gen <= local_tlb_gen)) { >> /* >> * The TLB is already up to date in respect to f->new_tlb_gen. >> * While the core might be still behind mm_tlb_gen, checking >> * mm_tlb_gen unnecessarily would have negative caching effects >> * so avoid it. >> */ >> - return; >> + goto done; > Does this affect the performance numbers from aa44284960d5 ("x86/mm/tlb: > Avoid reading mm_tlb_gen when possible")? It depends on how many batched flushes that workload had. From the looks of it, they're all one page: madvise(addr + i, pgsize, MADV_DONTNEED); so there shouldn't be *much* batching in play. But, it wouldn't hurt to re-run them in either case.