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 23CF0C61DA4 for ; Mon, 6 Feb 2023 09:42:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229808AbjBFJmz (ORCPT ); Mon, 6 Feb 2023 04:42:55 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41892 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229448AbjBFJmx (ORCPT ); Mon, 6 Feb 2023 04:42:53 -0500 Received: from gentwo.de (gentwo.de [161.97.139.209]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id ABF9B76AF for ; Mon, 6 Feb 2023 01:42:50 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gentwo.de; s=default; t=1675676566; bh=HZzQ2iIvouqD7dUVVUrUzA9tkZZK0Oxxi7YTpggp7Uc=; h=Date:From:To:cc:Subject:In-Reply-To:References:From; b=jWr3N/DCjBdsWN/UIiQpuOGxzTsU2kBYG8UYdvSRK+v+bDUAwRsq/I0KDRhuD1wvY QaS5265+QjBwrrrWLCpK5LDwNWCNvr5tCcjsz83PqlnZ+31/P73Py6CwTBTT5LdsT7 bmB78f6c9DMHWYVvqU4Y6g+AvnJvHqeoHIGhs4LpBWi02NmA3zyGqLf1nCmnxSIng4 4kpgAHKBaI9mTZR8xnHiMgROEi+Yxv96BeXRZvmhmp+/1TRhwyz5IpMurqSYSwf5bk 0l+ThQodj26bTgl/Tc3CgEOgX0Fg+MbKPhol8d19B0zqj0RMq/4T+WJVexiTSANjIE 31Yx45FnxyIUQ== Received: by gentwo.de (Postfix, from userid 1001) id 16173B00159; Mon, 6 Feb 2023 10:42:46 +0100 (CET) Received: from localhost (localhost [127.0.0.1]) by gentwo.de (Postfix) with ESMTP id 14D5DB00100; Mon, 6 Feb 2023 10:42:46 +0100 (CET) Date: Mon, 6 Feb 2023 10:42:46 +0100 (CET) From: Christoph Lameter To: Marcelo Tosatti cc: Aaron Tomlin , Frederic Weisbecker , Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 3/5] mm/vmstat: use cmpxchg loop in cpu_vm_stats_fold In-Reply-To: Message-ID: <47a289f0-ae96-e0e6-c579-70ec61fff384@gentwo.de> References: <20230201195013.881721887@redhat.com> <20230201195104.460373427@redhat.com> <5615572-974e-74cc-6c34-1de618b777cf@gentwo.de> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 3 Feb 2023, Marcelo Tosatti wrote: > > Isnt there some lock/serializtion to stall the kernel until you are done? > > Not that i know of. Anyway, an additional datapoint is: > > "Software defined PLC" > (https://www.redhat.com/en/blog/software-defined-programmable-logic-controller-introduction), > applications > can perform system calls in their time sensitive loop. > > One example of an opensource software is OpenPLC. > > One would like to avoid interruptions for those cases as well. Well allowing sytem calls during "time sensitiveness" implies it is not that sensitive to vmstat updates which have a smaller impact than system calls. Unless we are talking about virtual system calls like gettimeofday or clock_gettime. These do not enter the kernel if configured correctly.