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Tue, 22 Mar 2022 05:27:10 GMT Received: from b03ledav002.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 3BE62136065; Tue, 22 Mar 2022 05:27:10 +0000 (GMT) Received: from b03ledav002.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id A1E1613605D; Tue, 22 Mar 2022 05:26:53 +0000 (GMT) Received: from skywalker.linux.ibm.com (unknown [9.43.75.167]) by b03ledav002.gho.boulder.ibm.com (Postfix) with ESMTP; Tue, 22 Mar 2022 05:26:53 +0000 (GMT) X-Mailer: emacs 29.0.50 (via feedmail 11-beta-1 I) From: "Aneesh Kumar K.V" To: Yu Zhao , Andrew Morton , Linus Torvalds Cc: Andi Kleen , Catalin Marinas , Dave Hansen , Hillf Danton , Jens Axboe , Jesse Barnes , Johannes Weiner , Jonathan Corbet , Matthew Wilcox , Mel Gorman , Michael Larabel , Michal Hocko , Mike Rapoport , Rik van Riel , Vlastimil Babka , Will Deacon , Ying Huang , linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, page-reclaim@google.com, x86@kernel.org, Yu Zhao , Brian Geffon , Jan Alexander Steffens , Oleksandr Natalenko , Steven Barrett , Suleiman Souhlal , Daniel Byrne , Donald Carr , Holger =?utf-8?Q?Hoffst=C3=A4tte?= , Konstantin Kharlamov , Shuang Zhai , Sofia Trinh , Vaibhav Jain Subject: Re: [PATCH v9 06/14] mm: multi-gen LRU: minimal implementation In-Reply-To: <20220309021230.721028-7-yuzhao@google.com> References: <20220309021230.721028-1-yuzhao@google.com> <20220309021230.721028-7-yuzhao@google.com> Date: Tue, 22 Mar 2022 10:56:50 +0530 Message-ID: <877d8m7e1x.fsf@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: Ql37j01KajwgF00k2OgU6gOK2r3sWXEJ X-Proofpoint-GUID: DAQxEiwBayf4Zp-JJHxC8P33uRYSCots X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.850,Hydra:6.0.425,FMLib:17.11.64.514 definitions=2022-03-21_10,2022-03-21_01,2022-02-23_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 phishscore=0 impostorscore=0 malwarescore=0 clxscore=1015 priorityscore=1501 suspectscore=0 bulkscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2202240000 definitions=main-2203220028 Authentication-Results: imf14.hostedemail.com; dkim=pass header.d=ibm.com header.s=pp1 header.b=Yk1O5Lck; spf=pass (imf14.hostedemail.com: domain of aneesh.kumar@linux.ibm.com designates 148.163.158.5 as permitted sender) smtp.mailfrom=aneesh.kumar@linux.ibm.com; dmarc=pass (policy=none) header.from=ibm.com X-Rspam-User: X-Stat-Signature: ocm6ow4ujprmuqbjcq9gof7bwqugp8gd X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 89678100016 X-HE-Tag: 1647926856-295462 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: Yu Zhao writes: + > +static void inc_min_seq(struct lruvec *lruvec) > +{ > + int type; > + struct lru_gen_struct *lrugen = &lruvec->lrugen; > + > + VM_BUG_ON(!seq_is_valid(lruvec)); > + > + for (type = 0; type < ANON_AND_FILE; type++) { > + if (get_nr_gens(lruvec, type) != MAX_NR_GENS) > + continue; > + > + reset_ctrl_pos(lruvec, type, true); > + WRITE_ONCE(lrugen->min_seq[type], lrugen->min_seq[type] + 1); > + } > +} > + > +static bool try_to_inc_min_seq(struct lruvec *lruvec, bool can_swap) > +{ > + int gen, type, zone; > + bool success = false; > + struct lru_gen_struct *lrugen = &lruvec->lrugen; > + DEFINE_MIN_SEQ(lruvec); > + > + VM_BUG_ON(!seq_is_valid(lruvec)); > + > + for (type = !can_swap; type < ANON_AND_FILE; type++) { > + while (min_seq[type] + MIN_NR_GENS <= lrugen->max_seq) { > + gen = lru_gen_from_seq(min_seq[type]); > + > + for (zone = 0; zone < MAX_NR_ZONES; zone++) { > + if (!list_empty(&lrugen->lists[gen][type][zone])) > + goto next; > + } > + > + min_seq[type]++; > + } > +next: > + ; > + } > + > + /* see the comment on lru_gen_struct */ > + if (can_swap) { > + min_seq[LRU_GEN_ANON] = min(min_seq[LRU_GEN_ANON], min_seq[LRU_GEN_FILE]); > + min_seq[LRU_GEN_FILE] = max(min_seq[LRU_GEN_ANON], lrugen->min_seq[LRU_GEN_FILE]); > + } > + > + for (type = !can_swap; type < ANON_AND_FILE; type++) { > + if (min_seq[type] == lrugen->min_seq[type]) > + continue; > + > + reset_ctrl_pos(lruvec, type, true); > + WRITE_ONCE(lrugen->min_seq[type], min_seq[type]); > + success = true; > + } > + > + return success; > +} > + > +static void inc_max_seq(struct lruvec *lruvec, unsigned long max_seq) > +{ > + int prev, next; > + int type, zone; > + struct lru_gen_struct *lrugen = &lruvec->lrugen; > + > + spin_lock_irq(&lruvec->lru_lock); > + > + VM_BUG_ON(!seq_is_valid(lruvec)); > + > + if (max_seq != lrugen->max_seq) > + goto unlock; > + > + inc_min_seq(lruvec); Can this min seq update result in pages considered oldest become young. ie, if we had seq value of 0 - 3 and we need ageing, the new min seq and max_seq value will now become 1 - 4. What happens to pages in the generation value 0 which was oldest generation earlier and is youngest now. > + > + /* update the active/inactive LRU sizes for compatibility */ > + prev = lru_gen_from_seq(lrugen->max_seq - 1); > + next = lru_gen_from_seq(lrugen->max_seq + 1); > + > + for (type = 0; type < ANON_AND_FILE; type++) { > + for (zone = 0; zone < MAX_NR_ZONES; zone++) { > + enum lru_list lru = type * LRU_INACTIVE_FILE; > + long delta = lrugen->nr_pages[prev][type][zone] - > + lrugen->nr_pages[next][type][zone]; > + > + if (!delta) > + continue; > + > + __update_lru_size(lruvec, lru, zone, delta); > + __update_lru_size(lruvec, lru + LRU_ACTIVE, zone, -delta); > + } > + } > + > + for (type = 0; type < ANON_AND_FILE; type++) > + reset_ctrl_pos(lruvec, type, false); > + > + /* make sure preceding modifications appear */ > + smp_store_release(&lrugen->max_seq, lrugen->max_seq + 1); > +unlock: > + spin_unlock_irq(&lruvec->lru_lock); > +} > + .... + > +static int evict_folios(struct lruvec *lruvec, struct scan_control *sc, int swappiness) > +{ > + int type; > + int scanned; > + int reclaimed; > + LIST_HEAD(list); > + struct folio *folio; > + enum vm_event_item item; > + struct reclaim_stat stat; > + struct mem_cgroup *memcg = lruvec_memcg(lruvec); > + struct pglist_data *pgdat = lruvec_pgdat(lruvec); > + > + spin_lock_irq(&lruvec->lru_lock); > + > + scanned = isolate_folios(lruvec, sc, swappiness, &type, &list); > + > + if (try_to_inc_min_seq(lruvec, swappiness)) > + scanned++; we are doing this before we shrink the page list. Any reason to do this before? > + > + if (get_nr_gens(lruvec, LRU_GEN_FILE) == MIN_NR_GENS) > + scanned = 0;