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Wed, 31 Jan 2024 14:03:47 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id mJp5LENTumVaDwAAD6G6ig (envelope-from ); Wed, 31 Jan 2024 14:03:47 +0000 Date: Wed, 31 Jan 2024 15:03:47 +0100 From: Michal Hocko To: David Hildenbrand Cc: Yin Fengwei , linux-kernel@vger.kernel.org, Linus Torvalds , linux-mm@kvack.org, Andrew Morton , Matthew Wilcox , Ryan Roberts , Catalin Marinas , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Peter Zijlstra , Michael Ellerman , Christophe Leroy , "Naveen N. Rao" , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , Arnd Bergmann , linux-arch@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, "Huang, Ying" Subject: Re: [PATCH v1 0/9] mm/memory: optimize unmap/zap with PTE-mapped THP Message-ID: References: <20240129143221.263763-1-david@redhat.com> <4ef64fd1-f605-4ddf-82e6-74b5e2c43892@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 919A1A0003 X-Rspam-User: X-Stat-Signature: yhbgc4915hh41y4df4mq1wrsgzuhsred X-Rspamd-Server: rspam03 X-HE-Tag: 1706709829-676411 X-HE-Meta: U2FsdGVkX18JCeIrYZ0O9NqbCl+6I2KTqyNN8kKhcFinzEM9xxFl8PipoqeB8LCyPCcdX0GCLQcVT7fYh7eH4h3DZ0XdmSUTEDBc4ZE+X5nHoyvaZmFiwXhVkgwLybfCl7MHIWHXT0s+XZ3hmEUY1w0aESQ8eVH7Go8TJ2/I7Uz1WZrBj0WdlkDj7+WhhcGmeoZKovCVaoAZP6uEmSJF7aGNq3d/wMwWawbzMxNTgQclob0sfYQy3ocAs7MA2dOXwpgeyJ/vsXwNS5/thJbC5tAJnRcGQs04jC1mld1xnlShAbYAU13ZH07xiv1rPpVFl5IJjl4VqGWYkbWaDk4koRi6TZYjgzMyiG3HWPxxmX5lniziALQNqwbhq5nNjj8HaHle5v4DPUinorUmGwHQ3f8DOsgdpVOdsscgxloEV6v3nh9GtEKNdxY87gBhNH6TxhAduOS/+Elch14VFtbw+x9dFqS7gnJff/7doqExojAE5Uf4MGFtFi+4+cO6aS6BCIoQSXzuekIK8TIMNjPE8HCVvH58KhsTF+KQr7rx5Y/rZWAinOuAgJgN7YtEQ7d3EtdxJbo8r3eWfZkjsMHAPlHXDbrnImqGcEOpPHu84w8aAhdvBhExsYhcLTynhC6/ta2s+yq7vOhyJmJcx7IyJVl2og4NRpfMb81FUrkYvjCss+K1I5FghDHguR+drVacJJksiAcmBGYWSRNUKw1W6s8zbIS70DSfyNBSA0T5zh7Ou+pkO5K8ducBTS2BbDh5gsRWhi9YlO4d64pCXcQW5eZamgO6VtnJXJni02p0o34eWtcMtD+EmbLR/er7Q9iahyXU0FrjjQBVRH32qm0HDusd/JcznipJrYPHHiY3hdA/XxtxQ5AzVbtZGSYx+1Gel4JbrRiyV8ADmqPfz/FgOOxqAjyCTE6GGBV1pLQpZwrBNZLIsy2/icphT2ZiseQTryMX/4ztyBrxXA+HWzD r/NfEzuH ATtZxDTEdgurj8hmZ7ilAaWD7+5qIPqPB3L91D5sdJH5yTRtNolBOGOi/VRMplzxUidFM8bqB75ARwGlpXlRFQQtbGKYo6XddEzKAKFq5lTwLEW7wB1yLoeaT6O++ve/xrMzAr572k+RS7ouARUmwS/4ddgKEJUFhgP2xORdDXk/xPHC/RvV6SJp6s4rhfWKYVlExTZER+ohVsacapzpLu7ORI86GYzkvm5V7bHmp9T4zQ4EEw/5P6i7OZQ== 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: List-Subscribe: List-Unsubscribe: On Wed 31-01-24 11:16:01, David Hildenbrand wrote: [...] > This 10000 pages limit was introduced in 53a59fc67f97 ("mm: limit mmu_gather > batching to fix soft lockups on !CONFIG_PREEMPT") where we wanted to handle > soft-lockups. AFAIR at the time of this patch this was mostly just to put some cap on the number of batches to collect and free at once. If there is a lot of free memory and a large process exiting this could grow really high. Now that those pages^Wfolios can represent larger memory chunks it could mean more physical memory being freed but from which might make the operation take longer but still far from soft lockup triggering. Now latency might suck on !PREEMPT kernels with too many pages to free in a single batch but I guess this is somehow expected for this preemption model. The soft lockup has to be avoided because this can panic the machine in some configurations. -- Michal Hocko SUSE Labs