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 812B3EB64D9 for ; Thu, 15 Jun 2023 12:21:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240308AbjFOMVD (ORCPT ); Thu, 15 Jun 2023 08:21:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57984 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245029AbjFOMTn (ORCPT ); Thu, 15 Jun 2023 08:19:43 -0400 Received: from smtp-out2.suse.de (smtp-out2.suse.de [IPv6:2001:67c:2178:6::1d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5AEAA3C01 for ; Thu, 15 Jun 2023 05:17:55 -0700 (PDT) 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 A05051FE0D; Thu, 15 Jun 2023 12:16:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1686831411; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=86pO/5pX8I+6NSA3fZs+/KcyWC6lgb7caHW7+qPc8ko=; b=mTBdbL6oQEScJdyCDi72UHa9I2GLbRNJ5ZjBPYHndoipUG71Z4Xxu63EC27CX6SqH+vo9X FY6pdkkt8YRTcB27ib4YCNhwkeC/1pM5HqDnfft8LjxWV887AzC6Q1dGJNX59BghoFDaUU YdVK15054ieCTAdkL/LC09lbkfUFbLM= 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 8F73013A47; Thu, 15 Jun 2023 12:16:51 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id xmtlIjMBi2ScLQAAMHmgww (envelope-from ); Thu, 15 Jun 2023 12:16:51 +0000 Date: Thu, 15 Jun 2023 14:16:51 +0200 From: Michal Hocko To: =?utf-8?B?6LS65Lit5Z2k?= Cc: minchan@kernel.org, senozhatsky@chromium.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [External] Re: [RFC PATCH 1/3] zram: charge the compressed RAM to the page's memcgroup Message-ID: References: <20230615034830.1361853-1-hezhongkun.hzk@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu 15-06-23 19:58:37, 贺中坤 wrote: > Hi michal, glad to hear from you. > > > I am not really deeply familiar with zram implementation nor usage but > > how is the above allocation going to be charged without __GFP_ACCOUNT in > > the gfp mask? > > Yes，zs_malloc() did not charge compressed memory, even if we add this gfp. > so we need to implement this function in this patchset. But this flag should be > used to enable this feature. Let me check I understand. This patch on its own doesn't really do anything. You need the zs_malloc support implemented in patch 3 for this to have any effect. Even with that in place the zs_malloc doesn't follow the __GFP_ACCOUNT scheme we use for allocation tracking. Correct? > > Also what exactly is going to happen for the swap backed by the zram > > device? Your memcg might be hitting the hard limit and therefore > > swapping out. Wouldn't zs_malloc fail very likely under that condition > > making the swap effectively unusable? > > This is the key point, as i said above, zs_malloc() did not charge > compressed memory, > so zs_malloc will not fail under that condition. if the zram swap is > large enough, zs_malloc > never fails unless system OOM. so memory.max will be invalidated. I do not think this is answering my question. Or maybe I just misunderstand. Let me try again. Say you have a memcg under hard limit pressure so any further charge is going to fail. How can you reasonably implement zram back swapout if the memory is charged? -- Michal Hocko SUSE Labs