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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 X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 877869000398 X-Stat-Signature: f1ce7fzy3f9giwqeqra9899ktwurei5b Authentication-Results: imf23.hostedemail.com; dkim=pass header.d=suse.de header.s=susede2_rsa header.b=TSzDzbp6; dkim=pass header.d=suse.de header.s=susede2_ed25519 header.b=bsVPEyzG; spf=pass (imf23.hostedemail.com: domain of osalvador@suse.de designates 195.135.220.28 as permitted sender) smtp.mailfrom=osalvador@suse.de; dmarc=pass (policy=none) header.from=suse.de X-HE-Tag: 1633422240-612156 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 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