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[73.69.118.222]) by smtp.gmail.com with ESMTPSA id s56sm6917392qtk.9.2020.04.03.07.09.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 03 Apr 2020 07:09:56 -0700 (PDT) From: Pavel Tatashin To: linux-kernel@vger.kernel.org, akpm@linux-foundation.org, mhocko@suse.com, linux-mm@kvack.org, dan.j.williams@intel.com, shile.zhang@linux.alibaba.com, daniel.m.jordan@oracle.com, pasha.tatashin@soleen.com, ktkhai@virtuozzo.com, david@redhat.com, jmorris@namei.org, sashal@kernel.org, vbabka@suse.cz Subject: [PATCH v4 2/3] mm: initialize deferred pages with interrupts enabled Date: Fri, 3 Apr 2020 10:09:51 -0400 Message-Id: <20200403140952.17177-3-pasha.tatashin@soleen.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20200403140952.17177-1-pasha.tatashin@soleen.com> References: <20200403140952.17177-1-pasha.tatashin@soleen.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Initializing struct pages is a long task and keeping interrupts disabled for the duration of this operation introduces a number of problems. 1. jiffies are not updated for long period of time, and thus incorrect time is reported. See proposed solution and discussion here: lkml/20200311123848.118638-1-shile.zhang@linux.alibaba.com 2. It prevents farther improving deferred page initialization by allowing intra-node multi-threading. We are keeping interrupts disabled to solve a rather theoretical problem that was never observed in real world (See 3a2d7fa8a3d5). Lets keep interrupts enabled. In case we ever encounter a scenario where an interrupt thread wants to allocate large amount of memory this early in boot we can deal with that by growing zone (see deferred_grow_zone()) by the needed amount before starting deferred_init_memmap() threads. Before: [ 1.232459] node 0 initialised, 12058412 pages in 1ms After: [ 1.632580] node 0 initialised, 12051227 pages in 436ms Fixes: 3a2d7fa8a3d5 ("mm: disable interrupts while initializing deferred pages") Cc: stable@vger.kernel.org # 4.17+ Reported-by: Shile Zhang Signed-off-by: Pavel Tatashin Reviewed-by: Daniel Jordan Acked-by: Michal Hocko Acked-by: Vlastimil Babka --- include/linux/mmzone.h | 2 ++ mm/page_alloc.c | 20 +++++++------------- 2 files changed, 9 insertions(+), 13 deletions(-) diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index e84d448988b6..ac6a8245f063 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -723,6 +723,8 @@ typedef struct pglist_data { /* * Must be held any time you expect node_start_pfn, * node_present_pages, node_spanned_pages or nr_zones to stay constant. + * Also synchronizes pgdat->first_deferred_pfn during deferred page + * init. * * pgdat_resize_lock() and pgdat_resize_unlock() are provided to * manipulate node_size_lock without checking for CONFIG_MEMORY_HOTPLUG diff --git a/mm/page_alloc.c b/mm/page_alloc.c index d95bfd328107..5ffa8d7e5545 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1784,6 +1784,13 @@ static int __init deferred_init_memmap(void *data) BUG_ON(pgdat->first_deferred_pfn > pgdat_end_pfn(pgdat)); pgdat->first_deferred_pfn = ULONG_MAX; + /* + * Once we unlock here, the zone cannot be grown anymore, thus if an + * interrupt thread must allocate this early in boot, zone must be + * pre-grown prior to start of deferred page initialization. + */ + pgdat_resize_unlock(pgdat, &flags); + /* Only the highest zone is deferred so find it */ for (zid = 0; zid < MAX_NR_ZONES; zid++) { zone = pgdat->node_zones + zid; @@ -1806,8 +1813,6 @@ static int __init deferred_init_memmap(void *data) touch_nmi_watchdog(); } zone_empty: - pgdat_resize_unlock(pgdat, &flags); - /* Sanity check that the next zone really is unpopulated */ WARN_ON(++zid < MAX_NR_ZONES && populated_zone(++zone)); @@ -1849,17 +1854,6 @@ deferred_grow_zone(struct zone *zone, unsigned int order) pgdat_resize_lock(pgdat, &flags); - /* - * If deferred pages have been initialized while we were waiting for - * the lock, return true, as the zone was grown. The caller will retry - * this zone. We won't return to this function since the caller also - * has this static branch. - */ - if (!static_branch_unlikely(&deferred_pages)) { - pgdat_resize_unlock(pgdat, &flags); - return true; - } - /* * If someone grew this zone while we were waiting for spinlock, return * true, as there might be enough pages already. -- 2.17.1