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 998B7C43334 for ; Fri, 8 Jul 2022 11:40:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237907AbiGHLkm (ORCPT ); Fri, 8 Jul 2022 07:40:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37232 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237509AbiGHLki (ORCPT ); Fri, 8 Jul 2022 07:40:38 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 7307B24F14 for ; Fri, 8 Jul 2022 04:40:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1657280436; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=wXQSLj7N0OPVrbql97FSOxJxi1gzgZ5rqCr//cm7fcI=; b=ctTYfaJZENyaLzHZGGSUnTypAT5BM65S/TWKanlgrszc+buYAt6BNk8I+2mRKBlKeV7lZS eZGUhXqedatkcAkp+e1roOUK+JbDbxgIsb0ksbVXR+2E4K+uD01hyZfWWAIyaMuX5r9hdb znOLEN4KdmBiYWQ1c0HBeLqK4kGgbps= Received: from mail-wm1-f69.google.com (mail-wm1-f69.google.com [209.85.128.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-294-R8C7gWqeOZq481-V6QcY9A-1; Fri, 08 Jul 2022 07:40:35 -0400 X-MC-Unique: R8C7gWqeOZq481-V6QcY9A-1 Received: by mail-wm1-f69.google.com with SMTP id v67-20020a1cac46000000b003a2be9fa09cso3884607wme.3 for ; Fri, 08 Jul 2022 04:40:35 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:message-id:date:mime-version:user-agent:subject :content-language:to:cc:references:from:organization:in-reply-to :content-transfer-encoding; bh=wXQSLj7N0OPVrbql97FSOxJxi1gzgZ5rqCr//cm7fcI=; b=h2k1JNd6ioN5AE3E9JRxu+jr2SUHm9JBzkWIzH2QIJ6+nQ+9D4bApPIxxu/q0vyWBM Chele8pndweiX06BuOYz0SLLY6q4c5DvBngNMrqptLQQATOV2uAp4xf8rEKvDnhNeTdX BcIhmrvo7rmQKszlO8RYp7LOgztkdK/2C3zARl3MgCDk9ADBsbpTKTES3IQtpDSLgAPT e134ZffHV8K/sYSp78rwik5PoG8oMvM640+h6icbeUd+b6yit+62fdiWZNlK2iLrR0IV XzGyyyYfbit6m3dQVPB0XhxN/vzTMkdxJ4Y5W0c1ZUGOvmlfpgalwFJgu06nsRSubYy4 en6w== X-Gm-Message-State: AJIora/dJoqEMqyPqj2p7U+OVEVIVJmcpfD2F9JnUloczT+ebZpSiYub MHO9486Ljxzd0/awtNwltg8wRj904RzB/8jKl/ZQPxvn/5BL4ODcBb+uq9TIPIqWRAoKstrUe5P UnOO9suvGHPv8nYtfZo3uVn+v X-Received: by 2002:a05:600c:3594:b0:3a2:b918:fc99 with SMTP id p20-20020a05600c359400b003a2b918fc99mr10447689wmq.46.1657280434239; Fri, 08 Jul 2022 04:40:34 -0700 (PDT) X-Google-Smtp-Source: AGRyM1sleJHiOa+wExrCN0/v8cRomeDekDTZvjWj0FUXinjSVbAalf0ycjKaPNjpP8yzp8DxqMxtlA== X-Received: by 2002:a05:600c:3594:b0:3a2:b918:fc99 with SMTP id p20-20020a05600c359400b003a2b918fc99mr10447657wmq.46.1657280434013; Fri, 08 Jul 2022 04:40:34 -0700 (PDT) Received: from ?IPV6:2003:cb:c702:6300:c44f:789a:59b5:91e9? (p200300cbc7026300c44f789a59b591e9.dip0.t-ipconnect.de. [2003:cb:c702:6300:c44f:789a:59b5:91e9]) by smtp.gmail.com with ESMTPSA id bh21-20020a05600c3d1500b003a2d6c623f3sm1954808wmb.19.2022.07.08.04.40.33 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 08 Jul 2022 04:40:33 -0700 (PDT) Message-ID: Date: Fri, 8 Jul 2022 13:40:32 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Subject: Re: [PATCH] x86/mm/tlb: ignore f->new_tlb_gen when zero Content-Language: en-US To: 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: David Hildenbrand Organization: Red Hat In-Reply-To: <20220708003053.158480-1-namit@vmware.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08.07.22 02:30, Nadav Amit wrote: > From: Nadav Amit > > Commit aa44284960d5 ("x86/mm/tlb: Avoid reading mm_tlb_gen when > possible") introduced an optimization of skipping the flush if the TLB > generation that is flushed (as provided in flush_tlb_info) was already > flushed. > > However, arch_tlbbatch_flush() does not provide any generation in > flush_tlb_info. As a result, try_to_unmap_one() would not perform any > TLB flushes. > > Fix it by checking whether f->new_tlb_gen is nonzero. Zero value is > anyhow is an invalid generation value. > > In addition, add the missing unlikely() and jump to get tracing right. > > Fixes: aa44284960d5 ("x86/mm/tlb: Avoid reading mm_tlb_gen when possible") > Reported-by: Hugh Dickins > Cc: Dave Hansen > Cc: Peter Zijlstra (Intel) > Cc: Andy Lutomirski > Signed-off-by: Nadav Amit > --- > arch/x86/mm/tlb.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > 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")? -- Thanks, David / dhildenb