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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id D4283C54EE9 for ; Wed, 28 Sep 2022 00:24:04 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 285D58E0109; Tue, 27 Sep 2022 20:24:04 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 2357D8E00C1; Tue, 27 Sep 2022 20:24:04 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0D6C38E0109; Tue, 27 Sep 2022 20:24:04 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id F3CA98E00C1 for ; Tue, 27 Sep 2022 20:24:03 -0400 (EDT) Received: from smtpin09.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id C2FD5A10D0 for ; Wed, 28 Sep 2022 00:24:03 +0000 (UTC) X-FDA: 79959596766.09.1D0D102 Received: from mail-ej1-f43.google.com (mail-ej1-f43.google.com [209.85.218.43]) by imf24.hostedemail.com (Postfix) with ESMTP id 5D33418000B for ; Wed, 28 Sep 2022 00:24:03 +0000 (UTC) Received: by mail-ej1-f43.google.com with SMTP id sd10so23983579ejc.2 for ; Tue, 27 Sep 2022 17:24:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc:subject:date; bh=yrRvoMA2qzsQLaNGkBWV3qKU0u6GXYvGhupTkuY6VEY=; b=N4SqAspV6MMkhBYCFIyWw1zoLE0Rd7s2OcFI1DceVn/pHLgQQpIGuPVe/Y5xz2rq7u 4AwEph2NeuV3pICsTTUzwRekddH0yOeND7JGqULNGiEUieyWRG6v6tDzpLe64Ks46WYl +E7aPSySmJM5rrRbU/QTtIuWWnrypBa5Nee0vTcASR26Pbtt3a1rnWEXJiAhZ0LuaF3z G0Kpy5TJl/IDsRofANqT6QeQSyO+rxKfvYX1lEVX/uIl1opJ/g6T4wX2v3xFu9sWUBhf nxjbUpm/gkJf8RF8BM1xVL9NUSyaLL/yweBBM9Jtss7d1JdDL1D0xSUAW2CB9lb+daDC gCuA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date; bh=yrRvoMA2qzsQLaNGkBWV3qKU0u6GXYvGhupTkuY6VEY=; b=ip/hwzvZdlWUQkE54Q+Q7ggR0pMwhWJ7QDhXztlBlGVQ6VU+Mr7KdfiP8yaNFsWJX8 WuV9bVCabDtIrh1ARsuBuIhW6mfWuHbCGX190xRWnOyoro/zKNa0I+J9pPufJjznBkSS aMpD1cTlCNJm6sK/SojmSm4qm5A2pRZHtEkGiWlKt+q7NlMTVvhYPtremijWwwPZsc8L GSvGzISnsj8amhBYZI1nbLe759xwxXVJPyZjqqUz6/KILeK2XEqosaGa4Vgzt9pvOBb+ A1kK+A4kVz3I9GpQVZ0XTn91k7h0x1zeUBCffpGUiXU3e6T+zJzjfvmEuuC1FXfdGomo qhxw== X-Gm-Message-State: ACrzQf2rrRDx4fnWeStMq1LTCCWHNZFuRo1iE3N6iHEx0jLghKlMCZaC 6EJ9hdrzz9YuiK/BVKL2sJgceWOTaTSwU/vst7w= X-Google-Smtp-Source: AMsMyM7eMgPelqF9CjnEbxsTqqXy6pmBZpLW9pueVjK2kG6gmJQBXY3G4jO1eBrNDVmQMCspWLB2ar5LjeuRSz4OCpA= X-Received: by 2002:a17:907:7eaa:b0:782:3d2b:20b0 with SMTP id qb42-20020a1709077eaa00b007823d2b20b0mr25078507ejc.746.1664324641882; Tue, 27 Sep 2022 17:24:01 -0700 (PDT) MIME-Version: 1.0 References: <20220921084302.43631-1-yangyicong@huawei.com> <20220921084302.43631-3-yangyicong@huawei.com> <168eac93-a6ee-0b2e-12bb-4222eff24561@arm.com> <8e391962-4e3a-5a56-64b4-78e8637e3b8c@huawei.com> In-Reply-To: <8e391962-4e3a-5a56-64b4-78e8637e3b8c@huawei.com> From: Barry Song <21cnbao@gmail.com> Date: Wed, 28 Sep 2022 13:23:50 +1300 Message-ID: Subject: Re: [PATCH v4 2/2] arm64: support batched/deferred tlb shootdown during page reclamation To: Yicong Yang Cc: Anshuman Khandual , yangyicong@hisilicon.com, corbet@lwn.net, peterz@infradead.org, arnd@arndb.de, linux-kernel@vger.kernel.org, darren@os.amperecomputing.com, huzhanyuan@oppo.com, lipeifeng@oppo.com, zhangshiming@oppo.com, guojian@oppo.com, realmz6@gmail.com, linux-mips@vger.kernel.org, openrisc@lists.librecores.org, linux-mm@kvack.org, x86@kernel.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, akpm@linux-foundation.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, wangkefeng.wang@huawei.com, xhao@linux.alibaba.com, prime.zeng@hisilicon.com, Barry Song , Nadav Amit , Mel Gorman , catalin.marinas@arm.com, will@kernel.org, linux-doc@vger.kernel.org Content-Type: text/plain; charset="UTF-8" ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1664324643; a=rsa-sha256; cv=none; b=Lqh06R4ky3IoubJuAVBJ6u7v3k+gaJjZTFGABgJJNdCzSnKLeY3Fqcq9Aj+zt6A1wmWzvp ewDxEcAqH4jAHzYOD/BvaAd8cTJKdAR1Dxpxw7PwMC1NslOOP3g2UDkmcFyZZ+RCESelbh kP22H8107R9Z70eqVVIj17O0hLdqBFo= ARC-Authentication-Results: i=1; imf24.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=N4SqAspV; spf=pass (imf24.hostedemail.com: domain of 21cnbao@gmail.com designates 209.85.218.43 as permitted sender) smtp.mailfrom=21cnbao@gmail.com; dmarc=pass (policy=none) header.from=gmail.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1664324643; h=from:from:sender: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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=yrRvoMA2qzsQLaNGkBWV3qKU0u6GXYvGhupTkuY6VEY=; b=wWxYmYUswf+eNoC3CQFZjXlXu91G+cJjUOPlG7vhoeqBSk8N/ohq9P5gHkY8nL0H54yZmg HIroM5q91gnpdxU9XjRVdq7NnkkL2jvy12Dfyo679ns15ddBWrqpBxDxj+lEEYXOZ40+ll hDB/+9ap4TvjAmH5DpxHFxDCu7oc4N4= X-Rspamd-Server: rspam10 X-Rspam-User: Authentication-Results: imf24.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=N4SqAspV; spf=pass (imf24.hostedemail.com: domain of 21cnbao@gmail.com designates 209.85.218.43 as permitted sender) smtp.mailfrom=21cnbao@gmail.com; dmarc=pass (policy=none) header.from=gmail.com X-Stat-Signature: znsizmcc1441c6cqt4byynpp7fhd5e98 X-Rspamd-Queue-Id: 5D33418000B X-HE-Tag: 1664324643-586284 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Sep 27, 2022 at 10:15 PM Yicong Yang wrote: > > On 2022/9/27 14:16, Anshuman Khandual wrote: > > [...] > > > > On 9/21/22 14:13, Yicong Yang wrote: > >> +static inline bool arch_tlbbatch_should_defer(struct mm_struct *mm) > >> +{ > >> + /* for small systems with small number of CPUs, TLB shootdown is cheap */ > >> + if (num_online_cpus() <= 4) > > > > It would be great to have some more inputs from others, whether 4 (which should > > to be codified into a macro e.g ARM64_NR_CPU_DEFERRED_TLB, or something similar) > > is optimal for an wide range of arm64 platforms. > > I have tested it on a 4-cpus and 8-cpus machine. but i have no machine with 5,6,7 cores. I saw improvement on 8-cpus machines and I found 4-cpus machines don't need this patch. so it seems safe to have if (num_online_cpus() < 8) > > Do you prefer this macro to be static or make it configurable through kconfig then > different platforms can make choice based on their own situations? It maybe hard to > test on all the arm64 platforms. Maybe we can have this default enabled on machines with 8 and more cpus and provide a tlbflush_batched = on or off to allow users enable or disable it according to their hardware and products. Similar example: rodata=on or off. Hi Anshuman, Will, Catalin, Andrew, what do you think about this approach? BTW, haoxin mentioned another important user scenarios for tlb bach on arm64: https://lore.kernel.org/lkml/393d6318-aa38-01ed-6ad8-f9eac89bf0fc@linux.alibaba.com/ I do believe we need it based on the expensive cost of tlb shootdown in arm64 even by hardware broadcast. > > Thanks. > > >> + return false;> + > >> +#ifdef CONFIG_ARM64_WORKAROUND_REPEAT_TLBI > >> + if (unlikely(this_cpu_has_cap(ARM64_WORKAROUND_REPEAT_TLBI))) > >> + return false; > >> +#endif > >> + > >> + return true; > >> +} > >> + > > > > [...] > > > > . > > Thanks Barry