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Wed, 21 Dec 2022 14:09:34 -0300 (-03) Message-ID: <20221221170436.292370701@redhat.com> User-Agent: quilt/0.66 Date: Wed, 21 Dec 2022 13:58:03 -0300 From: Marcelo Tosatti To: atomlin@atomlin.com, frederic@kernel.org Cc: cl@linux.com, tglx@linutronix.de, mingo@kernel.org, peterz@infradead.org, pauld@redhat.com, neelx@redhat.com, oleksandr@natalenko.name, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Marcelo Tosatti Subject: [PATCH v11 2/6] mm/vmstat: Use vmstat_dirty to track CPU-specific vmstat discrepancies References: <20221221165801.362118576@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.4 X-Rspam-User: X-Rspamd-Queue-Id: 050472001B X-Rspamd-Server: rspam01 X-Stat-Signature: hdn1aqbebcm1xfdp3ofx9owu83fxksen X-HE-Tag: 1671642649-781686 X-HE-Meta: U2FsdGVkX18wjLUUNKjyzoGeOphz6kMjAsml/wB6C5Akmpgsan/dfYql0Ouh00BWW0PFy4MqPXEbgC5YPjfP2wxPkHOMtb2Hra7AVkTReF6njUH9U474O/u7OCDYi/9lIXPXX+krkkNQOS2Vfp3RQ3T1y5/z/2tHfhjB5cvzxq+qW4lkF+Iy+YB2lhqEHhwRxfabBZGv/zQRqEwTsLWMHWXyz5mVf+yTbb2oS3QTOmpZO5MMRZy6wAcoCB7mppogcexpNDmL4BBEngPBXXPMDpYL2seSUMLGbcIlUzry3tBy1So8+wunSD0cHRqpwoR+ZYVPz4HBgLhnve9Y5pIxX+aYGAUGa6kDY6q+w9d7w50JIJnBlOyg6T7j3Fcu5YpmZkHmhs0oy3pe9nj8T9YfGdqa7ORjl9ePzQOAzZYWwenkw1fYz681tqu1Pn8+h+mkxP9WU9sYlrGyOOSTNSKbvOavvFd+32/ho997RABZBlAddBt2ZTQwCrNap+vA0Z16BjwJglkK69GhBwzEEsxugqA+FdrsQFMniIvljZQQAdtXgNnan4QalNn9WVJ84Cb/f84mlGdPh/UE2SAKzhZGQSSsxiJ/LHsE0FtsnHjLbH6qD0UKNeQ1vVcvYi7c9Cdp50NU4avw7jajt61A+pq3fiw7FTVQZgTXtDf2lPq75o7nP9ZXIOB/0VBQws5psS5mmyKtsyY8HxMGR+XI22B6F7C9Yy/bvkhDw93HhSqR5gFLFzEVA+ZF91sJEUguH8Nc1lYLKF0qYiVOllOwROFdDowPC5QbkXJo/ss/Te94bgZd1EV0pkiB/l1XiuOFUMtLcu/LH/JKZAIj9toT9wtgloCumRJQW+oUBXNgzYtT65CvmeZzTAtQd9t2DanDD+W8kpW2D0lKLT8Y32prl3I7Qhu75rEp4DaPuScbJdXoI9Q= 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: From: Aaron Tomlin This patch will now use the previously introduced CPU-specific variable namely vmstat_dirty to indicate if a vmstat differential/or imbalance is present for a given CPU. So, at the appropriate time, vmstat processing can be initiated. The hope is that this particular approach is "cheaper" when compared to need_update(). The idea is based on Marcelo's patch [1]. [1]: https://lore.kernel.org/lkml/20220204173554.763888172@fedora.localdomain/ Signed-off-by: Aaron Tomlin Signed-off-by: Marcelo Tosatti --- mm/vmstat.c | 48 ++++++++++++++---------------------------------- 1 file changed, 14 insertions(+), 34 deletions(-) Index: linux-2.6/mm/vmstat.c =================================================================== --- linux-2.6.orig/mm/vmstat.c +++ linux-2.6/mm/vmstat.c @@ -381,6 +381,7 @@ void __mod_zone_page_state(struct zone * x = 0; } __this_cpu_write(*p, x); + vmstat_mark_dirty(); preempt_enable_nested(); } @@ -417,6 +418,7 @@ void __mod_node_page_state(struct pglist x = 0; } __this_cpu_write(*p, x); + vmstat_mark_dirty(); preempt_enable_nested(); } @@ -606,6 +608,7 @@ static inline void mod_zone_state(struct if (z) zone_page_state_add(z, zone, item); + vmstat_mark_dirty(); } void mod_zone_page_state(struct zone *zone, enum zone_stat_item item, @@ -674,6 +677,7 @@ static inline void mod_node_state(struct if (z) node_page_state_add(z, pgdat, item); + vmstat_mark_dirty(); } void mod_node_page_state(struct pglist_data *pgdat, enum node_stat_item item, @@ -828,6 +832,14 @@ static int refresh_cpu_vm_stats(bool do_ int global_node_diff[NR_VM_NODE_STAT_ITEMS] = { 0, }; int changes = 0; + /* + * Clear vmstat_dirty before clearing the percpu vmstats. + * If interrupts are enabled, it is possible that an interrupt + * or another task modifies a percpu vmstat, which will + * set vmstat_dirty to true. + */ + vmstat_clear_dirty(); + for_each_populated_zone(zone) { struct per_cpu_zonestat __percpu *pzstats = zone->per_cpu_zonestats; #ifdef CONFIG_NUMA @@ -1957,35 +1969,6 @@ static void vmstat_update(struct work_st } /* - * Check if the diffs for a certain cpu indicate that - * an update is needed. - */ -static bool need_update(int cpu) -{ - pg_data_t *last_pgdat = NULL; - struct zone *zone; - - for_each_populated_zone(zone) { - struct per_cpu_zonestat *pzstats = per_cpu_ptr(zone->per_cpu_zonestats, cpu); - struct per_cpu_nodestat *n; - - /* - * The fast way of checking if there are any vmstat diffs. - */ - if (memchr_inv(pzstats->vm_stat_diff, 0, sizeof(pzstats->vm_stat_diff))) - return true; - - if (last_pgdat == zone->zone_pgdat) - continue; - last_pgdat = zone->zone_pgdat; - n = per_cpu_ptr(zone->zone_pgdat->per_cpu_nodestats, cpu); - if (memchr_inv(n->vm_node_stat_diff, 0, sizeof(n->vm_node_stat_diff))) - return true; - } - return false; -} - -/* * Switch off vmstat processing and then fold all the remaining differentials * until the diffs stay at zero. The function is used by NOHZ and can only be * invoked when tick processing is not active. @@ -1995,10 +1978,7 @@ void quiet_vmstat(void) if (system_state != SYSTEM_RUNNING) return; - if (!delayed_work_pending(this_cpu_ptr(&vmstat_work))) - return; - - if (!need_update(smp_processor_id())) + if (!is_vmstat_dirty()) return; /* @@ -2029,7 +2009,7 @@ static void vmstat_shepherd(struct work_ for_each_online_cpu(cpu) { struct delayed_work *dw = &per_cpu(vmstat_work, cpu); - if (!delayed_work_pending(dw) && need_update(cpu)) + if (!delayed_work_pending(dw) && per_cpu(vmstat_dirty, cpu)) queue_delayed_work_on(cpu, mm_percpu_wq, dw, 0); cond_resched();