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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 3F8D2C38A02 for ; Fri, 28 Oct 2022 13:12:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:Message-ID:In-Reply-To: Date:References:Subject:Cc:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=jXFpbCgmOVGyEfNSjaRZXqc+wFXlQ5TLQnjX3XuII6c=; b=mMkZoNzaqLI2l2 eY+3OECAgpIhnQysancE1zCKwaRgVM9J7jnMtdfaj1hkgPNPBSGy976BtHd1sa4ldXG+2m20/1+dq yG//VCTBA5/f+xvD/ajLQo36tPrOD6OGqxTUxqpHe+4g0mLL1g/AZmzuCpP5su0/SXgT2QXaiUSA1 2GTzGO0flyGQbDvdykm17AbNhjNwlXHzWxRLivGrUYdzZU17Acbhi/kRvKgzqurngziPTqTTn8YAF L5XlCLSDK+IsQwZNrgsLPkE8jsBtSBhIk9fntsE8EFFMW3AJ9EDBDBfVfy4JYEGkuEPmL11r+sRyM wfsIWTn0W9tFRQUE9JYQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1ooP9o-00HGZE-UM; Fri, 28 Oct 2022 13:12:20 +0000 Received: from mail-wr1-x42f.google.com ([2a00:1450:4864:20::42f]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1ooP9M-00HGML-Hc for linux-riscv@lists.infradead.org; Fri, 28 Oct 2022 13:11:54 +0000 Received: by mail-wr1-x42f.google.com with SMTP id z14so6534555wrn.7 for ; Fri, 28 Oct 2022 06:11:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20210112.gappssmtp.com; s=20210112; h=mime-version:user-agent:message-id:in-reply-to:date:references :subject:cc:to:from:from:to:cc:subject:date:message-id:reply-to; bh=+Aj7lCoa9R32lr+KR5EAOPwdoRP9ej39sPKRFvXXmKo=; b=EFIo+tctRNuBHWwWw1xOq1kEixfm3foZR690FRJu3AM3x8PYD0ZDLFys0bq0GHDw0q D+MTVPyEG1mTG0ZgdOgJq8+gjfvXKbovWD8hGjcbI7wWrksCjPBNiTntRvERjSr3G2+k Lu7JNnRQmZ6+8v+2wFsOY4k1EMCtFfmzGGyaZDJW+zI6dotPwQ2SHNssHmq5yH6XrLvw xSqtVUxuIWlv47NuYTEMe31KwKyXtoj47d/WfUsTDmeHSsavPPN1aNy232z2FiDj7IE2 kdVuMjIFXr8rqIXxZZe02eKvfiUGYKO5h8nAQjogNLBpf+5ZCJOnzUUb++YTPAQ3vG+E aVQg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=mime-version:user-agent:message-id:in-reply-to:date:references :subject:cc:to:from:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=+Aj7lCoa9R32lr+KR5EAOPwdoRP9ej39sPKRFvXXmKo=; b=qf+CpPt9u3MfmhRhSVQXraC3LWeysQJGCFlF5l3Fnv3+H/3f6GpKUwHULsT4/EOoe6 F9XXfV+063Wys0lQ5X7o3oxIuRs7KQ4D+YrxxjjmX0N8ZKoaRhbSIPb+7Ev+ZzTE5ycs 2io5Grig/B1Vaqsrj5TUmolzOUzZs53GNBnvp1p1J437R48y1yomWVnI5qk4P87vulOj /7ZhesqkZzjsLYH2Uged1HFCQVE4qd7WhDGT3gR6+GpQ6uUs6gElyjXpUd8sj4xNki8Y sKDaFGefv/C4xfbapSV2wc/kW/4ruRkPqIJAy+D5YfC+LxKNt1I6WDgrBwewHiBvZhHG ZEJg== X-Gm-Message-State: ACrzQf0aBVthOC5xE+A+f/P4UfWUOru1IuHYU6d+m+d11AY+zbarV3r7 y//8NvUVSsZ2hreWRuZ8qsODKw== X-Google-Smtp-Source: AMsMyM6YDLGx8tddVpugpJgNDAZlKMyecbRnjlokKyPGo/AAsO2SU74UqqxLLYtDEOG4bOxEAgjUZA== X-Received: by 2002:adf:df83:0:b0:236:6d5d:ff8b with SMTP id z3-20020adfdf83000000b002366d5dff8bmr18336437wrl.315.1666962704559; Fri, 28 Oct 2022 06:11:44 -0700 (PDT) Received: from localhost ([95.148.15.66]) by smtp.gmail.com with ESMTPSA id k21-20020a05600c1c9500b003bfaba19a8fsm4641180wms.35.2022.10.28.06.11.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 28 Oct 2022 06:11:43 -0700 (PDT) From: Punit Agrawal To: Yicong Yang Cc: Punit Agrawal , Barry Song <21cnbao@gmail.com>, , , , , , , , , , , , , , , , , , , , , , , , Barry Song , Nadav Amit , Mel Gorman , , , , Anshuman Khandual Subject: Re: [PATCH v4 2/2] arm64: support batched/deferred tlb shootdown during page reclamation 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> <87o7tx5oyx.fsf@stealth> Date: Fri, 28 Oct 2022 14:11:41 +0100 In-Reply-To: (Yicong Yang's message of "Fri, 28 Oct 2022 09:20:08 +0800") Message-ID: <87bkpw5bzm.fsf@stealth> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221028_061152_624211_33E048EA X-CRM114-Status: GOOD ( 22.83 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org Yicong Yang writes: > On 2022/10/27 22:19, Punit Agrawal wrote: >> >> [ Apologies for chiming in late in the conversation ] >> >> Anshuman Khandual writes: >> >>> On 9/28/22 05:53, Barry Song wrote: >>>> 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. >>> >>> No, sounds bit excessive. Kernel command line options should not be added >>> for every possible run time switch options. >>> >>>> >>>> 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. >>> >>> Alright, for now could we enable ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH selectively >>> with CONFIG_EXPERT and for num_online_cpus() > 8 ? >> >> When running the test program in the commit in a VM, I saw benefits from >> the patches at all sizes from 2, 4, 8, 32 vcpus. On the test machine, >> ptep_clear_flush() went from ~1% in the unpatched version to not showing >> up. >> > > Maybe you're booting VM on a server with more than 32 cores and Barry tested > on his 4 CPUs embedded platform. I guess a 4 CPU VM is not fully equivalent to > a 4 CPU real machine as the tbli and dsb in the VM may influence the host > as well. Yeah, I also wondered about this. I was able to test on a 6-core RK3399 based system - there the ptep_clear_flush() was only 0.10% of the overall execution time. The hardware seems to do a pretty good job of keeping the TLB flushing overhead low. [...] _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv