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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1D830C433FE for ; Wed, 30 Nov 2022 12:50:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235175AbiK3Muq (ORCPT ); Wed, 30 Nov 2022 07:50:46 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59786 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229613AbiK3Mum (ORCPT ); Wed, 30 Nov 2022 07:50:42 -0500 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9FD9B3D90E; Wed, 30 Nov 2022 04:50:41 -0800 (PST) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id 515121F8D4; Wed, 30 Nov 2022 12:50:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1669812640; h=from:from:reply-to: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=8ZGYbHjMMJD2KtxpoYl71o8+mthDszQIMORViCtN+H4=; b=TEYdT2ejsqxumwVeGAtrs/wb5t8Z7WykQ86E9LmitKLafwNZ3z4nIFifyvnAoyM2lSntZk 4ETEFoMHzkEz3lOxQ/oZ49G7lqHhgEx9C8HKAAVubxMqpZ9B4BG6KeTAM+reO31e5xywk0 aevyUeC9LoRpjosj/FGvwSFKdixPZHk= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 346E21331F; Wed, 30 Nov 2022 12:50:40 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id qHV9CqBRh2O3SgAAMHmgww (envelope-from ); Wed, 30 Nov 2022 12:50:40 +0000 Date: Wed, 30 Nov 2022 13:50:39 +0100 From: Michal Hocko To: Johannes Weiner Cc: Hugh Dickins , Andrew Morton , Linus Torvalds , Shakeel Butt , Stephen Rothwell , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: remove lock_page_memcg() from rmap Message-ID: References: <20221123181838.1373440-1-hannes@cmpxchg.org> <16dd09c-bb6c-6058-2b3-7559b5aefe9@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 29-11-22 14:08:34, Johannes Weiner wrote: [...] > Short of further restricting the pages that can be moved, I don't see > how we can get rid of the cgroup locks in rmap after all. :( :( > We can try limiting move candidates to present ptes. But maybe it's > indeed time to deprecate the legacy charge moving altogether, and get > rid of the entire complication. > > Hugh, Shakeel, Michal, what do you think? I do agree with Hugh that going part way will likely not solve the general maintenance burden. I am OK with dropping the functionality but we should at least add a big fat warning if anybody wants to enable memory.move_charge_at_immigrate. If there are any workload which absolutely depend on the feature (which would make them impossible to migrate to v2 btw) then we want to hear about that and address in some way. An incremental deprecation by limiting to present ptes sounds like this semantic change might get overlooked for an extended time. -- Michal Hocko SUSE Labs