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Wed, 16 Nov 2022 06:32:08 -0500 X-MC-Unique: 3SyP_G89O7uezsxfdM67-w-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 19DEA1C075B2; Wed, 16 Nov 2022 11:32:08 +0000 (UTC) Received: from localhost (ovpn-12-255.pek2.redhat.com [10.72.12.255]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 444E618EB4; Wed, 16 Nov 2022 11:32:06 +0000 (UTC) Date: Wed, 16 Nov 2022 19:32:03 +0800 From: Baoquan He To: Dennis Zhou Cc: Vlastimil Babka , kernel test robot , oe-kbuild-all@lists.linux.dev, Linux Memory Management List , 42.hyeyoo@gmail.com Subject: Re: [linux-next:master 5002/7443] include/linux/compiler_types.h:357:45: error: call to '__compiletime_assert_474' declared with attribute error: BUILD_BUG_ON failed: PERCPU_DYNAMIC_EARLY_SIZE < NR_KMALLOC_TYPES * KMALLOC_SHIFT_HIGH * sizeof(struct kmem_cache_cpu) Message-ID: References: <202211120436.HzD1i2yQ-lkp@intel.com> MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 3.1 on 10.11.54.5 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1668598334; a=rsa-sha256; cv=none; b=IM9L3QA+tcL4BGnvuQF4zV12rP2GUy3KJoAqsCIycAA0ydapPoRqZmFFqroZqjMix+TmI2 YCn2zFPc9NFLdUX11+TzV70IfqxmxiM2bqFU8sHI5QQjJ/qyo2nAZJT6aVr047Jw1mD9SN Memi20G0NCh7wyQ7YgDEdYHM+/Q+kNY= ARC-Authentication-Results: i=1; imf13.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=AHMaTUxu; spf=pass (imf13.hostedemail.com: domain of bhe@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=bhe@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1668598334; h=from:from:sender: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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=mVa3twZHE2UNisP2DdAwo7HXdl8QxAKPJ4XG4vak3xs=; b=7XdeTTL8jXGD8uUti73bdjIgNhhUoR0CljWCJF8Y8U5g5NsJlcnoiHx4A2aVod2ocYEsMC 1Ta7AeFVRco4XSjX/7CHFPuctaA+n/HoeCHBumrVv7AKGiHdBvGqp1mDc8MzNZw/EgG5dk o5jLxW/adNvVVmj27Qnq+vx49XSDmW0= X-Rspam-User: X-Stat-Signature: jkrreh4j5kgu8r55oduu9oxw9so54rou X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: AFADA20008 Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=AHMaTUxu; spf=pass (imf13.hostedemail.com: domain of bhe@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=bhe@redhat.com; dmarc=pass (policy=none) header.from=redhat.com X-HE-Tag: 1668598334-181942 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 11/15/22 at 12:00pm, Dennis Zhou wrote: > On Tue, Nov 15, 2022 at 05:08:52PM +0800, Baoquan He wrote: > > Hi Dennis, > > > > On 11/14/22 at 08:13pm, Dennis Zhou wrote: > > > Hi Vlastimil & Baoquan, > > > > > > On Mon, Nov 14, 2022 at 06:58:13PM +0100, Vlastimil Babka wrote: > > > > On 11/14/22 08:44, Baoquan He wrote: > > > > > Hi, > > > > > > > > > > I reproduced the build failure according to lkp report and made a patch > > > > > as below to fix it. > > > > > > > > > > From dae7dd9705015ce36db757e88c78802584f949b1 Mon Sep 17 00:00:00 2001 > > > > > From: Baoquan He > > > > > Date: Sun, 13 Nov 2022 18:08:27 +0800 > > > > > Subject: [PATCH] percpu: adjust the value of PERCPU_DYNAMIC_EARLY_SIZE > > > > > Content-type: text/plain > > > > > > > > > > LKP reported a build failure as below on the patch "mm/slub, percpu: > > > > > correct the calculation of early percpu allocation size" > > > > > > > > Since I have that patch in slab.git exposed to -next, should I take this fix > > > > too, to make things simpler? Dennis? > > > > > > > > > > I don't have any problems with you running a fix, but I'm not quite sure > > > this is the right fix. Though this might cause a trivial merge conflict > > > with: d667c94962c1 ("mm/percpu: remove unused PERCPU_DYNAMIC_EARLY_SLOTS") > > > in my percpu#for-6.2 branch. > > > > > > If I'm understanding this correctly, slub requires additional percpu > > > memory due to the use of 64k pages. By increasing > > > PERCPU_DYNAMIC_EARLY_SIZE, we solve the problem for 64k page users, but > > > require a few unnecessary pages that can bloat the size of subsequent > > > percpu chunks. Though, I'm not sure if that's an issue today for > > > embedded devices. > > > > Thanks for looking into this. > > > > I guess you are talking about PERCPU_DYNAMIC_EARLY_SIZE will impact the > > first dynamic chunk size of page first chunk, because the embed first > > chunk will take PERCPU_DYNAMIC_RESERVE. And the impact is done in below > > max() invacation. > > > > static struct pcpu_alloc_info * __init __flatten pcpu_build_alloc_info( > > size_t reserved_size, size_t dyn_size, > > size_t atom_size, > > pcpu_fc_cpu_distance_fn_t cpu_distance_fn) > > { > > ...... > > /* calculate size_sum and ensure dyn_size is enough for early alloc */ > > size_sum = PFN_ALIGN(static_size + reserved_size + > > max_t(size_t, dyn_size, PERCPU_DYNAMIC_EARLY_SIZE)); > > ...... > > } > > > > > > > > I think adding parity to PERCPU_DYNAMIC_EARLY_SIZE with > > > PERCPU_DYNAMIC_RESERVE is defined by BITS_PER_LONG is a safer option > > > here. A small TODO item would be to make PERCPU_DYNAMIC_RESERVE be a + > > > value instead of a max() with PERCPU_DYNAMIC_EARLY_SIZE. > > > > Hmm, the below change may not take power arch into account. Please > > check arch/powerpc/include/asm/page.h, seems the 32bit ppc could have > > 256K pages too. Adding PERCPU_DYNAMIC_EARLY_SIZE to 20K may cost extra > > memory during boot. But th left space of 1st dynamic chunk will join > > the later percpu dynamic allocation, it's not wasted, right? > > > > Not sure if I got your point. > > > > > > Ah, I'm not familiar with all the PAGE_SIZE and word length > combinations. > > The first chunk is smaller in the embedded case with the assumption that > static percpu variables are highly accessed along with the limited > initial allocations. While adding an additional 8KB is not the biggest > deal to the first chunk, this can cause the unit_size for subsequent > chunks to be larger. For example, x86 unit size jumps in powers of 2 due > to alignment and packing against an allocation size of 2MB. So if we're > at say 60KB for the first chunk, subsequent chunks could be 64KB. But > adding 8KB, we'd go from 60KB -> 68KB and a chunk size of 64KB -> 128KB. I could have misunderstanding about the first chunk usage and percpu code. Below is my personal uderstanding about the 1st chunk size and how PERCPU_DYNAMIC_EARLY_SIZE could impact it, please help point out if I am wrong. ~~~ Abstract the definition of them here for reference. /* * Percpu allocator can serve percpu allocations before slab is * initialized which allows slab to depend on the percpu allocator. * The following parameter decide how much resource to preallocate * for this. Keep PERCPU_DYNAMIC_RESERVE equal to or larger than ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ * PERCPU_DYNAMIC_EARLY_SIZE. ~~~~~~~~~~~~~~~~~~~~~ */ #define PERCPU_DYNAMIC_EARLY_SIZE (12 << 10) ...... #if BITS_PER_LONG > 32 #define PERCPU_DYNAMIC_RESERVE (28 << 10) #else #define PERCPU_DYNAMIC_RESERVE (20 << 10) #endif >From above definition, we can see that no matter how big PERCPU_DYNAMIC_RESERVE is , it's >= PERCPU_DYNAMIC_EARLY_SIZE as the code comment says. So the max() in pcpu_build_alloc_info() won't impact the embeded 1st chunk at all. So, PERCPU_DYNAMIC_EARLY_SIZE can only impact the page 1st chunk case, namely when calling pcpu_page_first_chunk() to do that. In pcpu_page_first_chunk(), we don't provide dyn_size, so with the help of max(), it will get final dyn_size as PERCPU_DYNAMIC_EARLY_SIZE. This is the only place where PERCPU_DYNAMIC_EARLY_SIZE takes effect on percpu. However, the atom size of page 1st chunk is PAGE_SIZE, it doesn't have the issue of possible bloating unit_size by the atom size, e.g 2M on x86_64. Since pcpu_page_first_chunk() is the fallback of pcpu_embed_first_chunk(), if we decide to provide PERCPU_DYNAMIC_RESERVE as the current value, why we grudge setting it as the smaller value, 20K, whether it's 32bit or 64bit. > > If not `BITS_PER_LONG >32`, we could do `PAGE_SHIFT > 12`. > > Thanks, > Dennis > > > > > > > --- > > > diff --git a/include/linux/percpu.h b/include/linux/percpu.h > > > index f1ec5ad1351c..22ce3271eed2 100644 > > > --- a/include/linux/percpu.h > > > +++ b/include/linux/percpu.h > > > @@ -42,7 +42,11 @@ > > > * larger than PERCPU_DYNAMIC_EARLY_SIZE. > > > */ > > > #define PERCPU_DYNAMIC_EARLY_SLOTS 128 > > > +#if BITS_PER_LONG > 32 > > > +#define PERCPU_DYNAMIC_EARLY_SIZE (20 << 10) > > > +#else > > > #define PERCPU_DYNAMIC_EARLY_SIZE (12 << 10) > > > +#endif > > > > > > /* > > > * PERCPU_DYNAMIC_RESERVE indicates the amount of free area to piggy > > > > > > > >