From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BA5B181ABE for ; Thu, 28 Mar 2024 14:46:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711637216; cv=none; b=fT/Yu0OVf7GDNTVrwk66zVS/HkoUySrvHYyILmZHHGcJN+pNI8lAxqPiLwVAXddNUFerGX1kbKPko4yca+iYU3woSbbkZloCbftpK8klKuPQY8Efn470H82Haco1KPZ2JL8aE/cv4Sc0HNlsOXQP39OzlmFWYRuyWvHOOWHuE3A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711637216; c=relaxed/simple; bh=GBmw0u0sk6raQ2641DnVvOuLU698WOt7jEDcGyiJFg8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=PdJlwXH93d2OtpbFl0clkxczQkihH8RrG+oJtPuEZO4A5gebSfkzgCLF5RYyTr10ahxJ1tlgGTrznhb0EzUiow3qztrhDJNUOeA+53nYPa4gdA30V+O5r+a7oUGcBQdm7RR1bfjnahDss3BFX4CsucasvsjZic+oiDKgd8kqVzs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=OEGxisbI; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="OEGxisbI" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1711637213; 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: in-reply-to:in-reply-to:references:references; bh=cPAuSkYgy+MUhS8KdVZMaOcLOllCqbF/NxocVA82LN4=; b=OEGxisbIvkcODE/KYGbXLdMJX1OcpXd4c8b9WzIOiTzQyQlS+Lq4+qVJ3cqIub4lhBZKkZ /PzGTH1u+IT7C+DO/GTZFceXrffpVYQdzB30YQvKf6gjClpvY0YVKaoyPYuGOLpvPKfmJK dQy9Hg4UAxAE1jxZfKQXleqcC/B/JFQ= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-509-PInHT43-PY2c36tojWgsHg-1; Thu, 28 Mar 2024 10:46:50 -0400 X-MC-Unique: PInHT43-PY2c36tojWgsHg-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 1E226801906; Thu, 28 Mar 2024 14:46:49 +0000 (UTC) Received: from localhost (unknown [10.72.116.12]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 4FD432024517; Thu, 28 Mar 2024 14:46:48 +0000 (UTC) Date: Thu, 28 Mar 2024 22:46:39 +0800 From: Baoquan He To: Mike Rapoport Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, x86@kernel.org, linuxppc-dev@lists.ozlabs.org, akpm@linux-foundation.org Subject: Re: [PATCH v2 4/6] mm/mm_init.c: remove meaningless calculation of zone->managed_pages in free_area_init_core() Message-ID: References: <20240325145646.1044760-1-bhe@redhat.com> <20240325145646.1044760-5-bhe@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.4 On 03/28/24 at 11:53am, Mike Rapoport wrote: > On Thu, Mar 28, 2024 at 04:32:38PM +0800, Baoquan He wrote: > > On 03/25/24 at 10:56pm, Baoquan He wrote: > > > > > > /* > > > - * Set an approximate value for lowmem here, it will be adjusted > > > - * when the bootmem allocator frees pages into the buddy system. > > > - * And all highmem pages will be managed by the buddy system. > > > + * Initialize zone->managed_pages as 0 , it will be reset > > > + * when memblock allocator frees pages into buddy system. > > > */ > > > - zone_init_internals(zone, j, nid, freesize); > > > + zone_init_internals(zone, j, nid, 0); > > > > Here, we should initialize zone->managed_pages as zone->present_pages > > because later page_group_by_mobility_disabled need be set according to > > zone->managed_pages. Otherwise page_group_by_mobility_disabled will be > > set to 1 always. I will sent out v3. > > With zone->managed_pages set to zone->present_pages we won't account for > the reserved memory for initialization of page_group_by_mobility_disabled. The old zone->managed_pages didn't account for the reserved pages either. It's calculated by (zone->present_pages - memmap_pages). memmap pages only is only a very small portion, e.g on x86_64, 4K page size, assuming size of struct page is 64, then it's 1/64 of system memory. On arm64, 64K page size, it's 1/1024 of system memory. And about the setting of page_group_by_mobility_disabled, the compared value pageblock_nr_pages * MIGRATE_TYPES which is very small. On x86_64, it's 4M*6=24M; on arm64 with 64K size and 128M*6=768M which should be the biggest among ARCH-es. if (vm_total_pages < (pageblock_nr_pages * MIGRATE_TYPES)) page_group_by_mobility_disabled = 1; else page_group_by_mobility_disabled = 0; So page_group_by_mobility_disabled could be set to 1 only on system with very little memory which is very rarely seen. And setting zone->managed_pages as zone->present_pages is very close to its old value: (zone->present_pages - memmap_pages). Here we don't need be very accurate, just a rough value. > > As watermarks are still not initialized at the time build_all_zonelists() > is called, we may use nr_all_pages - nr_kernel_pages instead of > nr_free_zone_pages(), IMO. nr_all_pages should be fine if we take this way. nr_kernel_pages is a misleading name, it's all low memory pages excluding kernel reserved apges. nr_all_pages is all memory pages including highmema and exluding kernel reserved pages. Both is fine to me. The first one is easier, simply setting zone->managed_pages as zone->present_pages. The 2nd way is a little more accurate. > > > From a17b0921b4bd00596330f61ee9ea4b82386a9fed Mon Sep 17 00:00:00 2001 > > From: Baoquan He > > Date: Thu, 28 Mar 2024 16:20:15 +0800 > > Subject: [PATCH] mm/mm_init.c: set zone's ->managed_pages as ->present_pages > > for now > > Content-type: text/plain > > > > Because page_group_by_mobility_disabled need be set according to zone's > > managed_pages later. > > > > Signed-off-by: Baoquan He > > --- > > mm/mm_init.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/mm/mm_init.c b/mm/mm_init.c > > index cc24e7958c0c..dd875f943cbb 100644 > > --- a/mm/mm_init.c > > +++ b/mm/mm_init.c > > @@ -1561,7 +1561,7 @@ static void __init free_area_init_core(struct pglist_data *pgdat) > > * Initialize zone->managed_pages as 0 , it will be reset > > * when memblock allocator frees pages into buddy system. > > */ > > - zone_init_internals(zone, j, nid, 0); > > + zone_init_internals(zone, j, nid, zone->present_pages); > > > > if (!size) > > continue; > > -- > > 2.41.0 > > > > > > > > > > if (!size) > > > continue; > > > @@ -1915,6 +1878,7 @@ void __init free_area_init(unsigned long *max_zone_pfn) > > > check_for_memory(pgdat); > > > } > > > > > > + calc_nr_kernel_pages(); > > > memmap_init(); > > > > > > /* disable hash distribution for systems with a single node */ > > > -- > > > 2.41.0 > > > > > > > -- > Sincerely yours, > Mike. >