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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9D588C00140 for ; Wed, 10 Aug 2022 06:33:30 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 39FA68E0003; Wed, 10 Aug 2022 02:33:30 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 326968E0001; Wed, 10 Aug 2022 02:33:30 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1C7DD8E0003; Wed, 10 Aug 2022 02:33:30 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 064DE8E0001 for ; Wed, 10 Aug 2022 02:33:30 -0400 (EDT) Received: from smtpin01.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id D6291C03F8 for ; Wed, 10 Aug 2022 06:33:29 +0000 (UTC) X-FDA: 79782716538.01.59F48F5 Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) by imf26.hostedemail.com (Postfix) with ESMTP id BC9DA140185 for ; Wed, 10 Aug 2022 06:33:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1660113208; x=1691649208; h=from:to:cc:subject:references:date:in-reply-to: message-id:mime-version; bh=QIhNWhaFzPd7M69D/251lZz3jAISvGoccdRGMCoXT6o=; b=dByAo+hgBXvU+eJ4KnBjaAvTe/dpO1HqvVRs3o6QPzY+WghLdQwcbMtm G4mulUs5chs/w29Tb/vgnAN2xudDu+c0vyu7k7RzUa3LRe8+2UP1HCMKZ 3ELB7G1CO8iAMQATA8SAtZxA84czV7/yonS4msoluA3CAtIXwkU8r0RHJ 5Ej6rBb6MWP5HlaR+w4L7idCXy7qORHSvk+pK82D/WRt3/M8aB4FeMHYM mLWt0uGTbzvK8MGhdRj0HI5dV0vzr1IefWRJ7NnopB23O3bg2De+fCugt /bRUVxPjDpKDToHzNULoZYuXaGFFNRpgh5cmdgB96Je/y/TogXEYhCHGp Q==; X-IronPort-AV: E=McAfee;i="6400,9594,10434"; a="316955887" X-IronPort-AV: E=Sophos;i="5.93,226,1654585200"; d="scan'208";a="316955887" Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Aug 2022 23:33:08 -0700 X-IronPort-AV: E=Sophos;i="5.93,226,1654585200"; d="scan'208";a="932771834" Received: from yhuang6-desk2.sh.intel.com (HELO yhuang6-desk2.ccr.corp.intel.com) ([10.238.208.55]) by fmsmga005-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Aug 2022 23:33:05 -0700 From: "Huang, Ying" To: Peter Xu Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Minchan Kim , David Hildenbrand , Nadav Amit , Andrew Morton , Hugh Dickins , Vlastimil Babka , Andrea Arcangeli , Andi Kleen , "Kirill A . Shutemov" Subject: Re: [PATCH v3 6/7] mm/swap: Cache maximum swapfile size when init swap References: <20220809220100.20033-1-peterx@redhat.com> <20220809220100.20033-7-peterx@redhat.com> Date: Wed, 10 Aug 2022 14:33:02 +0800 In-Reply-To: <20220809220100.20033-7-peterx@redhat.com> (Peter Xu's message of "Tue, 9 Aug 2022 18:00:59 -0400") Message-ID: <87y1vwehgh.fsf@yhuang6-desk2.ccr.corp.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=ascii ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1660113209; 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=gjXNe1HXTF1u/my4JvYWc3XYK+vg1LhPIHm0Jh9P/6w=; b=JW8TuxwhMZbB+tWjePrTB4ydOk/xivYTnFn7kYttyodrDot7ycepGWp9zoYertu5XD22/w f4q10fZBSqKYgbAMv//pEmmXQKIZy0mRqcjB5c94mW7zE0nmggXmCX37AAC/tA86dL3BB/ NzyR03GETrG3WweiAY55eKh2O9PcwhI= ARC-Authentication-Results: i=1; imf26.hostedemail.com; dkim=none ("invalid DKIM record") header.d=intel.com header.s=Intel header.b=dByAo+hg; dmarc=pass (policy=none) header.from=intel.com; spf=pass (imf26.hostedemail.com: domain of ying.huang@intel.com designates 192.55.52.88 as permitted sender) smtp.mailfrom=ying.huang@intel.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1660113209; a=rsa-sha256; cv=none; b=H9CAmHWSG1MCfZ6Y7eW/M2ENmIy1wEL6oxcw1Jokq0wKp0fVekljmkgpyCmhGsJmmpF+qR rzjRRQzjwE8Ocn84NG8BWseVs4ezmZfud6iWTNRzkeZDwxgDkPupwZOBMrN9RH/D3LJC2l xfaBgxQrkwU+1RSGkK9zM0/MAgJdReU= X-Rspamd-Queue-Id: BC9DA140185 X-Rspamd-Server: rspam03 X-Rspam-User: Authentication-Results: imf26.hostedemail.com; dkim=none ("invalid DKIM record") header.d=intel.com header.s=Intel header.b=dByAo+hg; dmarc=pass (policy=none) header.from=intel.com; spf=pass (imf26.hostedemail.com: domain of ying.huang@intel.com designates 192.55.52.88 as permitted sender) smtp.mailfrom=ying.huang@intel.com X-Stat-Signature: qu4ker7ducybqx6dny1uh97fsecdp13i X-HE-Tag: 1660113208-165261 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: Peter Xu writes: > We used to have swapfile_maximum_size() fetching a maximum value of > swapfile size per-arch. > > As the caller of max_swapfile_size() grows, this patch introduce a variable > "swapfile_maximum_size" and cache the value of old max_swapfile_size(), so > that we don't need to calculate the value every time. > > Caching the value in swapfile_init() is safe because when reaching the > phase we should have initialized all the relevant information. Here the > major arch to look after is x86, which defines the max size based on L1TF > mitigation. > > Here both X86_BUG_L1TF or l1tf_mitigation should have been setup properly > when reaching swapfile_init(). As a reference, the code path looks like > this for x86: > > - start_kernel > - setup_arch > - early_cpu_init > - early_identify_cpu --> setup X86_BUG_L1TF > - parse_early_param > - l1tf_cmdline --> set l1tf_mitigation > - check_bugs > - l1tf_select_mitigation --> set l1tf_mitigation > - arch_call_rest_init > - rest_init > - kernel_init > - kernel_init_freeable > - do_basic_setup > - do_initcalls --> calls swapfile_init() (initcall level 4) > > The swapfile size only depends on swp pte format on non-x86 archs, so > caching it is safe too. > > Since at it, rename max_swapfile_size() to arch_max_swapfile_size() because > arch can define its own function, so it's more straightforward to have > "arch_" as its prefix. At the meantime, keep the swapfile_maximum_size() > function to fetch the value from the cache initialized in swapfile_init(). > > Signed-off-by: Peter Xu > --- > arch/x86/mm/init.c | 2 +- > mm/swapfile.c | 10 +++++++++- > 2 files changed, 10 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c > index 82a042c03824..9121bc1b9453 100644 > --- a/arch/x86/mm/init.c > +++ b/arch/x86/mm/init.c > @@ -1054,7 +1054,7 @@ void update_cache_mode_entry(unsigned entry, enum page_cache_mode cache) > } > > #ifdef CONFIG_SWAP > -unsigned long max_swapfile_size(void) > +unsigned long arch_max_swapfile_size(void) > { > unsigned long pages; > > diff --git a/mm/swapfile.c b/mm/swapfile.c > index 1fdccd2f1422..794fa37bd0c3 100644 > --- a/mm/swapfile.c > +++ b/mm/swapfile.c > @@ -63,6 +63,7 @@ EXPORT_SYMBOL_GPL(nr_swap_pages); > /* protected with swap_lock. reading in vm_swap_full() doesn't need lock */ > long total_swap_pages; > static int least_priority = -1; > +static unsigned long swapfile_maximum_size; > > static const char Bad_file[] = "Bad swap file entry "; > static const char Unused_file[] = "Unused swap file entry "; > @@ -2816,11 +2817,16 @@ unsigned long generic_max_swapfile_size(void) > } > > /* Can be overridden by an architecture for additional checks. */ > -__weak unsigned long max_swapfile_size(void) > +__weak unsigned long arch_max_swapfile_size(void) > { > return generic_max_swapfile_size(); > } > > +unsigned long max_swapfile_size(void) > +{ > + return swapfile_maximum_size; > +} > + It appears unnecessary to hide a variable with a function. Why not just use the variable directly. Best Regards, Huang, Ying > static unsigned long read_swap_header(struct swap_info_struct *p, > union swap_header *swap_header, > struct inode *inode) > @@ -3677,6 +3683,8 @@ static int __init swapfile_init(void) > for_each_node(nid) > plist_head_init(&swap_avail_heads[nid]); > > + swapfile_maximum_size = arch_max_swapfile_size(); > + > return 0; > } > subsys_initcall(swapfile_init);