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 4DC7EC6FD18 for ; Wed, 19 Apr 2023 11:19:54 +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:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=bttBFHvmtg7MDzK7IjI2CJ/Mfuzh4V0LHG1T8d3FMLs=; b=YSmNi+B/SkGj2h x4hYxiCWLXBJMA82/3caeI+kU2gOU2Kmpd4ra+/cCgsn5xlDokqqWjYADGMQPcouDpnbYTP8Eyndh lfad6gctsfEY5iNX3eL22HZGxZ66x1d5VWpxrSDhoto5JzvCtiRrhcml+583K9KGhN9708ZNz3d5R tdDCnxPEDeYWAPfq9wx6tjkRRWCMpkm1wU4OO/Co1yg0Baku/ofEPG04WaxBcbw9DgWeVPmhlk1k0 cpyCOxyZ/jXQzirGTYiECmXNgKYXbMUPhcBGxwMc/iChvkIzzU4ZKbQEtoS7NtzCnt6rf/99A/IX4 JzsYFGtBGaNhxeY4D6jQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1pp5pz-0059y2-0D; Wed, 19 Apr 2023 11:18:59 +0000 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1pp5pw-0059w8-1q for linux-arm-kernel@lists.infradead.org; Wed, 19 Apr 2023 11:18:57 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1681903134; 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: in-reply-to:in-reply-to:references:references; bh=yk2MXIcMGsqVm4bpeyyiPIAlxJgEs4vB5F4slfGpqbs=; b=bnuGJcsLdXXl+pGkEdCAUMQRs0WiTDv0xAXOggGpVKFX0XEAvxgd3QSU80uHbAtgoLhPUK ROnfc1YQjTrvZ6EhiBpiMzO6eFGwv775+bnk5rzgDMzxypl3rn7kF4bRz4AobLDeIg3wgv GecKYANSClbhYpX48NkT/7/sPYIxsZY= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-169-jmHSCGkANleXDaHYHeFrNA-1; Wed, 19 Apr 2023 07:18:51 -0400 X-MC-Unique: jmHSCGkANleXDaHYHeFrNA-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 59BDC101A54F; Wed, 19 Apr 2023 11:18:49 +0000 (UTC) Received: from tpad.localdomain (ovpn-112-2.gru2.redhat.com [10.97.112.2]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 75C83492B05; Wed, 19 Apr 2023 11:18:48 +0000 (UTC) Received: by tpad.localdomain (Postfix, from userid 1000) id C0514401344A1; Wed, 19 Apr 2023 08:01:41 -0300 (-03) Date: Wed, 19 Apr 2023 08:01:41 -0300 From: Marcelo Tosatti To: Peter Zijlstra Cc: Frederic Weisbecker , Yair Podemsky , linux@armlinux.org.uk, mpe@ellerman.id.au, npiggin@gmail.com, christophe.leroy@csgroup.eu, hca@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com, borntraeger@linux.ibm.com, svens@linux.ibm.com, davem@davemloft.net, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, will@kernel.org, aneesh.kumar@linux.ibm.com, akpm@linux-foundation.org, arnd@arndb.de, keescook@chromium.org, paulmck@kernel.org, jpoimboe@kernel.org, samitolvanen@google.com, ardb@kernel.org, juerg.haefliger@canonical.com, rmk+kernel@armlinux.org.uk, geert+renesas@glider.be, tony@atomide.com, linus.walleij@linaro.org, sebastian.reichel@collabora.com, nick.hawkins@hpe.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, sparclinux@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, vschneid@redhat.com, dhildenb@redhat.com, alougovs@redhat.com Subject: Re: [PATCH 3/3] mm/mmu_gather: send tlb_remove_table_smp_sync IPI only to CPUs in kernel mode Message-ID: References: <20230404134224.137038-1-ypodemsk@redhat.com> <20230404134224.137038-4-ypodemsk@redhat.com> <20230405195457.GC365912@hirez.programming.kicks-ass.net> <20230406133206.GN386572@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20230406133206.GN386572@hirez.programming.kicks-ass.net> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.9 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230419_041856_702305_CD3C167D X-CRM114-Status: GOOD ( 26.43 ) X-BeenThere: linux-arm-kernel@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-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Apr 06, 2023 at 03:32:06PM +0200, Peter Zijlstra wrote: > On Thu, Apr 06, 2023 at 09:49:22AM -0300, Marcelo Tosatti wrote: > > > > > 2) Depends on the application and the definition of "occasional". > > > > > > > > For certain types of applications (for example PLC software or > > > > RAN processing), upon occurrence of an event, it is necessary to > > > > complete a certain task in a maximum amount of time (deadline). > > > > > > If the application is properly NOHZ_FULL and never does a kernel entry, > > > it will never get that IPI. If it is a pile of shit and does kernel > > > entries while it pretends to be NOHZ_FULL it gets to keep the pieces and > > > no amount of crying will get me to care. > > > > I suppose its common practice to use certain system calls in latency > > sensitive applications, for example nanosleep. Some examples: > > > > 1) cyclictest (nanosleep) > > cyclictest is not a NOHZ_FULL application, if you tihnk it is, you're > deluded. On the field (what end-users do on production): cyclictest runs on NOHZ_FULL cores. PLC type programs run on NOHZ_FULL cores. So accordingly to physical reality i observe, i am not deluded. > > 2) PLC programs (nanosleep) > > What's a PLC? Programmable Logic Circuit? Programmable logic controller. > > A system call does not necessarily have to take locks, does it ? > > This all is unrelated to locks OK. > > Or even if application does system calls, but runs under a VM, > > then you are requiring it to never VM-exit. > > That seems to be a goal for performance anyway. Not sure what you mean. > > This reduces the flexibility of developing such applications. > > Yeah, that's the cards you're dealt, deal with it. This is not what happens on the field. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel