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 X-Spam-Level: X-Spam-Status: No, score=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_MUTT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2E08AC46470 for ; Tue, 21 May 2019 06:43:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F017721773 for ; Tue, 21 May 2019 06:43:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1558421028; bh=RnXLYhfY6lh0LSaoZsZoiyKf5U+jGs1qWIeePKBc4oc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=vcQR7KK7mzrzKc1Sa1NchS1SEFJ375kmaIRxxO8MXGC8vxF0ywdYHApNGe/FLpzoQ 8Tquv45ZucZ8X5RzD+4k/1StpNxb6tmEpO3A5bZiFSXPg+mP3eWDAvq1M2nLi+zOsY 7BwbKrYMGbct10iGjMhDNm+dRa5+5XcjXwAecC8w= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726738AbfEUGnr (ORCPT ); Tue, 21 May 2019 02:43:47 -0400 Received: from mx2.suse.de ([195.135.220.15]:55498 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726247AbfEUGnq (ORCPT ); Tue, 21 May 2019 02:43:46 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 7F1A5AD12; Tue, 21 May 2019 06:24:22 +0000 (UTC) Date: Tue, 21 May 2019 08:24:21 +0200 From: Michal Hocko To: Minchan Kim Cc: Andrew Morton , LKML , linux-mm , Johannes Weiner , Tim Murray , Joel Fernandes , Suren Baghdasaryan , Daniel Colascione , Shakeel Butt , Sonny Rao , Brian Geffon , linux-api@vger.kernel.org Subject: Re: [RFC 6/7] mm: extend process_madvise syscall to support vector arrary Message-ID: <20190521062421.GD32329@dhcp22.suse.cz> References: <20190520035254.57579-1-minchan@kernel.org> <20190520035254.57579-7-minchan@kernel.org> <20190520092258.GZ6836@dhcp22.suse.cz> <20190521024820.GG10039@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190521024820.GG10039@google.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 21-05-19 11:48:20, Minchan Kim wrote: > On Mon, May 20, 2019 at 11:22:58AM +0200, Michal Hocko wrote: > > [Cc linux-api] > > > > On Mon 20-05-19 12:52:53, Minchan Kim wrote: > > > Currently, process_madvise syscall works for only one address range > > > so user should call the syscall several times to give hints to > > > multiple address range. > > > > Is that a problem? How big of a problem? Any numbers? > > We easily have 2000+ vma so it's not trivial overhead. I will come up > with number in the description at respin. Does this really have to be a fast operation? I would expect the monitor is by no means a fast path. The system call overhead is not what it used to be, sigh, but still for something that is not a hot path it should be tolerable, especially when the whole operation is quite expensive on its own (wrt. the syscall entry/exit). I am not saying we do not need a multiplexing API, I am just not sure we need it right away. Btw. there was some demand for other MM syscalls to provide a multiplexing API (e.g. mprotect), maybe it would be better to handle those in one go? -- Michal Hocko SUSE Labs