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 6ABDFC61D9B for ; Wed, 22 Nov 2023 11:36:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343689AbjKVLgP (ORCPT ); Wed, 22 Nov 2023 06:36:15 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43758 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1343665AbjKVLgM (ORCPT ); Wed, 22 Nov 2023 06:36:12 -0500 Received: from out-173.mta0.migadu.com (out-173.mta0.migadu.com [IPv6:2001:41d0:1004:224b::ad]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0E92C197 for ; Wed, 22 Nov 2023 03:36:06 -0800 (PST) Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1700652964; 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=A+u2pUc5K7L9escf+xjmfFFM1fdziTV6mQ+Rd8WwzS0=; b=fDn25h0qKBHq/fMrjbngwj79njZzsgyV1I4eAKKfA7fRDxCt+V5FniRnClzSsWqG0sBNDa 3pOVW9X8p35Gpucxvwtf2hlLbVprHTxvgO/jVDWYfZnvz34Gj3b3MY4816lmp2Ly6qbKyn SPj7UamJrW+hq9MQ96eyOR2IIyu07/Q= Date: Wed, 22 Nov 2023 19:35:56 +0800 MIME-Version: 1.0 Subject: Re: [PATCH v5 6/9] slub: Delay freezing of partial slabs Content-Language: en-US To: Vlastimil Babka , Mark Brown Cc: cl@linux.com, 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 , Matthew Wilcox References: <20231102032330.1036151-1-chengming.zhou@linux.dev> <20231102032330.1036151-7-chengming.zhou@linux.dev> <4f3bc1bd-ea87-465d-b58a-0ed57b15187b@sirena.org.uk> <83ff4b9e-94f1-8b35-1233-3dd414ea4dfe@suse.cz> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Chengming Zhou In-Reply-To: <83ff4b9e-94f1-8b35-1233-3dd414ea4dfe@suse.cz> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023/11/22 17:37, Vlastimil Babka wrote: > On 11/20/23 19:49, Mark Brown wrote: >> On Thu, Nov 02, 2023 at 03:23:27AM +0000, chengming.zhou@linux.dev wrote: >>> From: Chengming Zhou >>> >>> Now we will freeze slabs when moving them out of node partial list to >>> cpu partial list, this method needs two cmpxchg_double operations: >>> >>> 1. freeze slab (acquire_slab()) under the node list_lock >>> 2. get_freelist() when pick used in ___slab_alloc() >> >> Recently -next has been failing to boot on a Raspberry Pi 3 with an arm >> multi_v7_defconfig and a NFS rootfs, a bisect appears to point to this >> patch (in -next as c8d312e039030edab25836a326bcaeb2a3d4db14) as having >> introduced the issue. I've included the full bisect log below. >> >> When we see problems we see RCU stalls while logging in, for example: > > Can you try this, please? > Great! I manually disabled __CMPXCHG_DOUBLE to reproduce the problem, and this patch can solve the machine hang problem. BTW, I also did the performance testcase on the machine with 128 CPUs. stress-ng --rawpkt 128 --rawpkt-ops 100000000 base patched 2.22s 2.35s 2.21s 3.14s 2.19s 4.75s Found this atomic version performance numbers are not stable. Should I change back to reuse the slab->__unused (mapcount) field? Or should we check "s->flags & __CMPXCHG_DOUBLE" in slab_set/clear_node_partial() to avoid using the atomic version? Thanks! > ----8<---- > From 000030c1ff055ef6a2ca624d0142f08f3ef19d51 Mon Sep 17 00:00:00 2001 > From: Vlastimil Babka > Date: Wed, 22 Nov 2023 10:32:41 +0100 > Subject: [PATCH] mm/slub: try to fix hangs without cmpxchg64/128 > > If we don't have cmpxchg64/128 and resort to slab_lock()/slab_unlock() > which uses PG_locked, we can get RMW with the newly introduced > slab_set/clear_node_partial() operation that modify PG_workingset so all > the operations have to be atomic now. > > Signed-off-by: Vlastimil Babka > --- > mm/slub.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/mm/slub.c b/mm/slub.c > index bcb5b2c4e213..f2cdb81ab02e 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -522,7 +522,7 @@ static __always_inline void slab_unlock(struct slab *slab) > struct page *page = slab_page(slab); > > VM_BUG_ON_PAGE(PageTail(page), page); > - __bit_spin_unlock(PG_locked, &page->flags); > + bit_spin_unlock(PG_locked, &page->flags); > } > > static inline bool > @@ -2127,12 +2127,12 @@ static inline bool slab_test_node_partial(const struct slab *slab) > > static inline void slab_set_node_partial(struct slab *slab) > { > - __set_bit(PG_workingset, folio_flags(slab_folio(slab), 0)); > + set_bit(PG_workingset, folio_flags(slab_folio(slab), 0)); > } > > static inline void slab_clear_node_partial(struct slab *slab) > { > - __clear_bit(PG_workingset, folio_flags(slab_folio(slab), 0)); > + clear_bit(PG_workingset, folio_flags(slab_folio(slab), 0)); > } > > /*