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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BCD14C433F5 for ; Tue, 5 Oct 2021 08:24:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A1E6961409 for ; Tue, 5 Oct 2021 08:24:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233286AbhJEIZy (ORCPT ); Tue, 5 Oct 2021 04:25:54 -0400 Received: from smtp-out1.suse.de ([195.135.220.28]:51268 "EHLO smtp-out1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230286AbhJEIZu (ORCPT ); Tue, 5 Oct 2021 04:25:50 -0400 Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 7CBA2223F3; Tue, 5 Oct 2021 08:23:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1633422239; h=from:from:reply-to: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=mSvxM5C6EzXCJb+jzr0CptvMNBt5k5JXIfSsVkx5rks=; b=TSzDzbp6C7l2AyGK2ULc0m6HRsYSrZRuP1Tkmvope3p52tIIEhPcJJA6Lx3E4ZbLL/x1Z1 K5PbI1qm41/m33jVtWSty7pkG7gCT8fM7WBR++Wp3hbCByyVORArlVXMWKMtt1TGlY0AJB iLmPwrsIdDMCpCgMcdieiNZMmP7K094= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1633422239; h=from:from:reply-to: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=mSvxM5C6EzXCJb+jzr0CptvMNBt5k5JXIfSsVkx5rks=; b=bsVPEyzGga2BRGr9qDifD94JaCdHXocXLT2bkXbsx61oGeAu9rxBcBzBZFYhhf+JKj00mb W6+zd1mbYnmLYiCw== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 5605B13A78; Tue, 5 Oct 2021 08:23:59 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id xVieFJ8LXGEIYwAAMHmgww (envelope-from ); Tue, 05 Oct 2021 08:23:59 +0000 MIME-Version: 1.0 Date: Tue, 05 Oct 2021 10:23:59 +0200 From: Oscar Salvador To: Mike Kravetz Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, David Hildenbrand , Michal Hocko , Zi Yan , Muchun Song , Naoya Horiguchi , David Rientjes , "Aneesh Kumar K . V" , Andrew Morton Subject: Re: [PATCH v3 1/5] hugetlb: add demote hugetlb page sysfs interfaces In-Reply-To: <20211001175210.45968-2-mike.kravetz@oracle.com> References: <20211001175210.45968-1-mike.kravetz@oracle.com> <20211001175210.45968-2-mike.kravetz@oracle.com> User-Agent: Roundcube Webmail Message-ID: <04e66e73b17c367d3f4b2b40e0cd7e17@suse.de> X-Sender: osalvador@suse.de Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021-10-01 19:52, Mike Kravetz wrote: > +static int demote_pool_huge_page(struct hstate *h, nodemask_t > *nodes_allowed) > + __must_hold(&hugetlb_lock) > +{ > + int rc = 0; > + > + lockdep_assert_held(&hugetlb_lock); > + > + /* We should never get here if no demote order */ > + if (!h->demote_order) > + return rc; Probably add a warning here? If we should never reach this but we do, then something got screwed along the way and we might want to know. > +static ssize_t demote_store(struct kobject *kobj, > + struct kobj_attribute *attr, const char *buf, size_t len) > +{ > + unsigned long nr_demote; > + unsigned long nr_available; > + nodemask_t nodes_allowed, *n_mask; > + struct hstate *h; > + int err; > + int nid; > + > + err = kstrtoul(buf, 10, &nr_demote); > + if (err) > + return err; > + h = kobj_to_hstate(kobj, &nid); > + > + /* Synchronize with other sysfs operations modifying huge pages */ > + mutex_lock(&h->resize_lock); > + > + spin_lock_irq(&hugetlb_lock); > + if (nid != NUMA_NO_NODE) { > + init_nodemask_of_node(&nodes_allowed, nid); > + n_mask = &nodes_allowed; > + } else { > + n_mask = &node_states[N_MEMORY]; > + } Cannot the n_mask dance be outside the locks? That does not need to be protected, right? > + > + while (nr_demote) { > + /* > + * Check for available pages to demote each time thorough the > + * loop as demote_pool_huge_page will drop hugetlb_lock. > + * > + * NOTE: demote_pool_huge_page does not yet drop hugetlb_lock > + * but will when full demote functionality is added in a later > + * patch. > + */ > + if (nid != NUMA_NO_NODE) > + nr_available = h->free_huge_pages_node[nid]; > + else > + nr_available = h->free_huge_pages; > + nr_available -= h->resv_huge_pages; > + if (!nr_available) > + break; > + > + if (!demote_pool_huge_page(h, n_mask)) > + break; Is it possible that when demote_pool_huge_page() drops the lock, h->resv_huge_pages change? Or that can only happen under h->resize_lock? > + > + nr_demote--; > + } > + > + spin_unlock_irq(&hugetlb_lock); > + mutex_unlock(&h->resize_lock); > + > + return len; > +} > +HSTATE_ATTR_WO(demote); > + > +static ssize_t demote_size_show(struct kobject *kobj, > + struct kobj_attribute *attr, char *buf) > +{ > + struct hstate *h; > + unsigned long demote_size; > + int nid; > + > + h = kobj_to_hstate(kobj, &nid); > + demote_size = h->demote_order; This has already been pointed out. > + > + return sysfs_emit(buf, "%lukB\n", > + (unsigned long)(PAGE_SIZE << h->demote_order) / SZ_1K); > +} > + > +static ssize_t demote_size_store(struct kobject *kobj, > + struct kobj_attribute *attr, > + const char *buf, size_t count) > +{ > + struct hstate *h, *t_hstate; > + unsigned long demote_size; > + unsigned int demote_order; > + int nid; This is just a nit-pick, but what is t_hstate? demote_hstate might be more descriptive. > + > + demote_size = (unsigned long)memparse(buf, NULL); > + > + t_hstate = size_to_hstate(demote_size); > + if (!t_hstate) > + return -EINVAL; > + demote_order = t_hstate->order; > + > + /* demote order must be smaller hstate order */ "must be smaller than" -- Oscar Salvador SUSE Labs