From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michal Hocko Subject: Re: [RFC 0/7] introduce memory hinting API for external process Date: Tue, 21 May 2019 08:34:21 +0200 Message-ID: <20190521063421.GG32329@dhcp22.suse.cz> References: <20190520035254.57579-1-minchan@kernel.org> <20190521014452.GA6738@bombadil.infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20190521014452.GA6738@bombadil.infradead.org> Sender: linux-kernel-owner@vger.kernel.org To: Matthew Wilcox Cc: Minchan Kim , 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 List-Id: linux-api@vger.kernel.org [linux-api] On Mon 20-05-19 18:44:52, Matthew Wilcox wrote: > On Mon, May 20, 2019 at 12:52:47PM +0900, Minchan Kim wrote: > > IMHO we should spell it out that this patchset complements MADV_WONTNEED > > and MADV_FREE by adding non-destructive ways to gain some free memory > > space. MADV_COLD is similar to MADV_WONTNEED in a way that it hints the > > kernel that memory region is not currently needed and should be reclaimed > > immediately; MADV_COOL is similar to MADV_FREE in a way that it hints the > > kernel that memory region is not currently needed and should be reclaimed > > when memory pressure rises. > > Do we tear down page tables for these ranges? That seems like a good > way of reclaiming potentially a substantial amount of memory. I do not think we can in general because this is a non-destructive operation. So at least we cannot tear down anonymous ptes (they will turn into swap entries). -- Michal Hocko SUSE Labs