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 4CE3EC4332F for ; Tue, 31 Oct 2023 02:51:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234818AbjJaCvL (ORCPT ); Mon, 30 Oct 2023 22:51:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59936 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233213AbjJaCvJ (ORCPT ); Mon, 30 Oct 2023 22:51:09 -0400 Received: from out-173.mta1.migadu.com (out-173.mta1.migadu.com [95.215.58.173]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 89D21ED for ; Mon, 30 Oct 2023 19:51:05 -0700 (PDT) Message-ID: <1dcc9969-da5b-4384-96d8-d03c835f198e@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1698720663; h=from:from:reply-to:subject:subject: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=sJGocIrvJOpdyaBLIvTHhgCm+KI16lXmHvQhyhxns3g=; b=DaUqksiPCxsm2P165op2FK7Z8jYJPEvUwhHu13OegGDh0aU+2Tiwtn57XudzehhMgoy8UP U8AQyOlzpM2iuBqadciwZOGw1uL+zJ+Ff+tWhoRJkd9utrVWeNs0dpamyA6/eApsWZlxwe Lbsc9oPhgDPuaSRlZzVNAb6sVtZuBZY= Date: Tue, 31 Oct 2023 10:50:33 +0800 MIME-Version: 1.0 Subject: Re: [RFC PATCH v3 0/7] slub: Delay freezing of CPU partial slabs Content-Language: en-US To: Christoph Lameter , vbabka@suse.cz Cc: penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org, roman.gushchin@linux.dev, 42.hyeyoo@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Chengming Zhou References: <20231024093345.3676493-1-chengming.zhou@linux.dev> <1199315b-63ce-4be4-8cde-b8b2fd29f91a@linux.dev> <7f70d130-c05a-3cb7-9509-41c21c3014fb@linux.com> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Chengming Zhou In-Reply-To: <7f70d130-c05a-3cb7-9509-41c21c3014fb@linux.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023/10/31 03:25, Christoph Lameter wrote: > On Sat, 28 Oct 2023, Chengming Zhou wrote: > >> 2. But for full slab (slab->freelist == NULL), PG_workingset is not much useful, we don't >>   safely know whether it's used as the cpu slab or not just from this flag. So __slab_free() >>   still rely on the "frozen" bit to know it. >> >> 3. And the maintaining of "frozen" has no extra cost now, since it's changed together with "freelist" >>   and other counter using cmpxchg, we already have the cmpxchg when start to use a slab as the cpu slab. >> >> Maybe I missed something, I don't know how to drop the frozen flag. > > > Maybe frozen is now = PG_Workingset | cmpxchg-frozen? > > The current scheme (which this series implemented) is: - node partial slabs: PG_Workingset (set or clear with per-node list_lock protection) - cpu partial slabs: !PG_Workingset - cpu slabs: !PG_Workingset && frozen (set or clear using cmpxchg together with freelist) - full slabs: !PG_Workingset As Vlastimil noted, it's possible to drop "frozen" bit for cpu slabs, but we keep it for performance, since we don't need to grab node list_lock to check whether PG_Workingset is set or not if the "frozen" bit is set. Thanks!