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([2a0c:5a80:1204:1500:37e7:8150:d9df:36f]) by smtp.gmail.com with ESMTPSA id h6sm4428856wmq.26.2022.02.09.01.45.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 09 Feb 2022 01:45:00 -0800 (PST) Message-ID: Subject: Re: [PATCH 0/2] mm/page_alloc: Remote per-cpu lists drain support From: Nicolas Saenz Julienne To: Xiongfeng Wang , akpm@linux-foundation.org Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, frederic@kernel.org, tglx@linutronix.de, mtosatti@redhat.com, mgorman@suse.de, linux-rt-users@vger.kernel.org, vbabka@suse.cz, cl@linux.com, paulmck@kernel.org, willy@infradead.org Date: Wed, 09 Feb 2022 10:45:00 +0100 In-Reply-To: <7c87f388-cc50-e9a1-17a7-802bb42656e4@huawei.com> References: <20220208100750.1189808-1-nsaenzju@redhat.com> <7c87f388-cc50-e9a1-17a7-802bb42656e4@huawei.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.42.3 (3.42.3-1.fc35) MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Xiongfeng, thanks for taking the time to look at this. On Wed, 2022-02-09 at 16:55 +0800, Xiongfeng Wang wrote: > Hi Nicolas， > > When I applied the patchset on the following commit and tested on QEMU, I came > accross the following CallTrace. > commit dd81e1c7d5fb126e5fbc5c9e334d7b3ec29a16a0 > > I wrote a userspace application to consume the memory. When the memory is used > out, the OOM killer is triggered and the following Calltrace is printed. I am > not sure if it is related to this patchset. But when I reverted this patchset, > the 'NULL pointer' Calltrace didn't show. It's a silly mistake on my part, while cleaning up the code I messed up one of the 'struct per_cpu_pages' accessors. This should fix it: ------------------------->8------------------------- diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 0caa7155ca34..e65b991c3dc8 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3279,7 +3279,7 @@ static void __drain_all_pages(struct zone *zone, bool force_all_cpus) has_pcps = true; } else { for_each_populated_zone(z) { - pcp = per_cpu_ptr(zone->per_cpu_pageset, cpu); + pcp = per_cpu_ptr(z->per_cpu_pageset, cpu); lp = rcu_dereference_protected(pcp->lp, mutex_is_locked(&pcpu_drain_mutex)); if (lp->count) { ------------------------->8------------------------- Thanks! -- Nicolás Sáenz