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 X-Spam-Level: X-Spam-Status: No, score=-17.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2B1FEC433B4 for ; Wed, 5 May 2021 01:56:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EBE3D61182 for ; Wed, 5 May 2021 01:56:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232222AbhEEB5C (ORCPT ); Tue, 4 May 2021 21:57:02 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:57296 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230474AbhEEB5A (ORCPT ); Tue, 4 May 2021 21:57:00 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1620179764; 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=XcTx3FgEa0ZtpV+h7gNoIIwMYnfs3k07HI6rrP4pOSc=; b=COprRlNYztG4D6fmRj4XbVBo1xqIMaa1V9HNtVvh+2S3W+3Se1SaTqz2MNpDHWpsW/PURo fjurJRG2+45Db0PlsrJjkas7LBdyteR3a2Ovpd0OSiTd/2+eMwTQeLaOwl7A1mhilHaNo6 eAzGUlHmFgxBGRz5L6MaEZ7qgkNNUOg= Received: from mail-qk1-f199.google.com (mail-qk1-f199.google.com [209.85.222.199]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-223-0HnL2xUGN0S7S2pewu66kw-1; Tue, 04 May 2021 21:56:02 -0400 X-MC-Unique: 0HnL2xUGN0S7S2pewu66kw-1 Received: by mail-qk1-f199.google.com with SMTP id i141-20020a379f930000b02902e94f6d938dso147624qke.5 for ; Tue, 04 May 2021 18:56:02 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:subject:to:cc:references:message-id:date :user-agent:mime-version:in-reply-to:content-transfer-encoding :content-language; bh=XcTx3FgEa0ZtpV+h7gNoIIwMYnfs3k07HI6rrP4pOSc=; b=cVdrSc+Xj0X2rrwkWnDQvPpcoOqiKwgebJ0PP9klEYFP9tEWy5B6D3mtqhZYBkia3N i5B6M+AMqggT0XODZiNbhU+RnMWkfn1UZlWpIgy99OqIYhlfSN1MUOC+aTa7xWRO5OyS uWmor9KaL4Pt+1GoqPPCLKi2GQyZo6hPYFWRK7e1qQqQrtq5CmI39ehp8ryjE0udiINn X/f7SQRM39LtsPKKQPY9RRzYyULfjoVW8IEueBJjxmQbjf7ZL0PRUyxtHNwavbqtgdl5 KE/Hbb8nPVZi78fPPXXsu9BRFQ0sK3CDZ9lVHgwTLW6s9et8titiLOpH9x3Vrv1qEROn Y9Zg== X-Gm-Message-State: AOAM5300FR1RTp9UccbBgDe5g2ghsPBH9ropEGWohvw5rQ1NiQq2/crR gupR2YIFQEFt5swO0ffCt62+riiuuNq75QDLj5DWNwSKV9GglsJPbO+j8xh+nxdwgeKCa1AEl3Q oIJ+41j1mGpNnGE00Q297s8yp X-Received: by 2002:a37:e50e:: with SMTP id e14mr27252305qkg.117.1620179762284; Tue, 04 May 2021 18:56:02 -0700 (PDT) X-Google-Smtp-Source: ABdhPJx8nWHVpb0cB/gzpuUMahqkiBpXMCaKBzc/pJJj7x33T7XaCXGRPc33nYRKs0lPFew7O9UEJw== X-Received: by 2002:a37:e50e:: with SMTP id e14mr27252286qkg.117.1620179762020; Tue, 04 May 2021 18:56:02 -0700 (PDT) Received: from llong.remote.csb ([2601:191:8500:76c0::cdbc]) by smtp.gmail.com with ESMTPSA id o189sm12603642qkd.60.2021.05.04.18.56.00 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 04 May 2021 18:56:01 -0700 (PDT) From: Waiman Long X-Google-Original-From: Waiman Long Subject: Re: [PATCH v2 2/2] mm: memcg/slab: Create a new set of kmalloc-cg- caches To: Vlastimil Babka , Johannes Weiner , Michal Hocko , Vladimir Davydov , Andrew Morton , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Roman Gushchin , Shakeel Butt Cc: linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org References: <20210504132350.4693-1-longman@redhat.com> <20210504132350.4693-3-longman@redhat.com> <3c952b24-94e4-3c54-b668-cac778ff5a77@suse.cz> Message-ID: <26ef8e5d-3a72-324f-4ef9-ead8c6251e70@redhat.com> Date: Tue, 4 May 2021 21:55:59 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.9.0 MIME-Version: 1.0 In-Reply-To: <3c952b24-94e4-3c54-b668-cac778ff5a77@suse.cz> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/4/21 12:01 PM, Vlastimil Babka wrote: > On 5/4/21 3:23 PM, Waiman Long wrote: >> There are currently two problems in the way the objcg pointer array >> (memcg_data) in the page structure is being allocated and freed. >> >> On its allocation, it is possible that the allocated objcg pointer >> array comes from the same slab that requires memory accounting. If this >> happens, the slab will never become empty again as there is at least >> one object left (the obj_cgroup array) in the slab. >> >> When it is freed, the objcg pointer array object may be the last one >> in its slab and hence causes kfree() to be called again. With the >> right workload, the slab cache may be set up in a way that allows the >> recursive kfree() calling loop to nest deep enough to cause a kernel >> stack overflow and panic the system. >> >> One way to solve this problem is to split the kmalloc- caches >> (KMALLOC_NORMAL) into two separate sets - a new set of kmalloc- >> (KMALLOC_NORMAL) caches for non-accounted objects only and a new set of >> kmalloc-cg- (KMALLOC_CGROUP) caches for accounted objects only. All >> the other caches can allow a mix of accounted and non-accounted objects. >> >> With this change, all the objcg pointer array objects will come from >> KMALLOC_NORMAL caches which won't have their objcg pointer arrays. So >> both the recursive kfree() problem and non-freeable slab problem >> are gone. >> >> The new KMALLOC_CGROUP is added between KMALLOC_NORMAL and >> KMALLOC_RECLAIM so that the first for loop in create_kmalloc_caches() >> will include the newly added caches without change. > Great, thanks I hope there would be also benefits to objcg arrays not > created for all the normal caches anymore (possibly poorly used due to > mix of accounted and non-accounted objects in the same cache) and perhaps > it's possible for you to quantify the reduction of those? Right, I will update the commit log to mention that as well. Thanks! >> Suggested-by: Vlastimil Babka >> Signed-off-by: Waiman Long > ... > >> @@ -321,6 +328,14 @@ kmalloc_caches[NR_KMALLOC_TYPES][KMALLOC_SHIFT_HIGH + 1]; >> >> static __always_inline enum kmalloc_cache_type kmalloc_type(gfp_t flags) >> { >> +#ifdef CONFIG_MEMCG_KMEM >> + /* >> + * KMALLOC_CGROUP for non-reclaimable and non-DMA object with >> + * accounting enabled. >> + */ >> + if ((flags & (__GFP_DMA | __GFP_RECLAIMABLE | __GFP_ACCOUNT)) == __GFP_ACCOUNT) >> + return KMALLOC_CGROUP; >> +#endif > This function was designed so that KMALLOC_NORMAL would be the first tested and > returned possibility, as it's expected to be the most common. What about the > following on top? > > ----8<---- > diff --git a/include/linux/slab.h b/include/linux/slab.h > index fca03c22ea7c..418c5df0305b 100644 > --- a/include/linux/slab.h > +++ b/include/linux/slab.h > @@ -328,30 +328,40 @@ kmalloc_caches[NR_KMALLOC_TYPES][KMALLOC_SHIFT_HIGH + 1]; > > static __always_inline enum kmalloc_cache_type kmalloc_type(gfp_t flags) > { > -#ifdef CONFIG_MEMCG_KMEM > /* > - * KMALLOC_CGROUP for non-reclaimable and non-DMA object with > - * accounting enabled. > + * The most common case is KMALLOC_NORMAL, so test for it > + * with a single branch for all flags that might affect it > */ > - if ((flags & (__GFP_DMA | __GFP_RECLAIMABLE | __GFP_ACCOUNT)) == __GFP_ACCOUNT) > - return KMALLOC_CGROUP; > + if (likely((flags & (__GFP_RECLAIMABLE > +#ifdef CONFIG_MEMCG_KMEM > + | __GFP_ACCOUNT > #endif > #ifdef CONFIG_ZONE_DMA > - /* > - * The most common case is KMALLOC_NORMAL, so test for it > - * with a single branch for both flags. > - */ > - if (likely((flags & (__GFP_DMA | __GFP_RECLAIMABLE)) == 0)) > + | __GFP_DMA > +#endif > + )) == 0)) > return KMALLOC_NORMAL; > > +#ifdef CONFIG_MEMCG_KMEM > /* > - * At least one of the flags has to be set. If both are, __GFP_DMA > - * is more important. > + * KMALLOC_CGROUP for non-reclaimable and non-DMA object with > + * accounting enabled. > */ > - return flags & __GFP_DMA ? KMALLOC_DMA : KMALLOC_RECLAIM; > -#else > - return flags & __GFP_RECLAIMABLE ? KMALLOC_RECLAIM : KMALLOC_NORMAL; > + if ((flags & (__GFP_ACCOUNT | __GFP_RECLAIMABLE > +#ifdef CONFIG_ZONE_DMApropose this to the customer as proposing this will create a lot of confusion > + | __GFP_DMA > +#endif > + )) == __GFP_ACCOUNT) > + return KMALLOC_CGROUP; > #endif > + > +#ifdef CONFIG_ZONE_DMA > + if (flags & __GFP_DMA) > + return KMALLOC_DMA; > +#endif > + > + /* if we got here, it has to be __GFP_RECLAIMABLE */ > + return KMALLOC_RECLAIM; > } > > /* > OK, I will make KMALLOC_NORMAL the first in the test. However the proposed change is a bit hard to read, so I will probably change it a bit. Thanks, Longman