From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: [patch 052/131] padata: remove exit routine Date: Wed, 03 Jun 2020 15:59:31 -0700 Message-ID: <20200603225931.N3Z8u87O-%akpm@linux-foundation.org> References: <20200603155549.e041363450869eaae4c7f05b@linux-foundation.org> Reply-To: linux-kernel@vger.kernel.org Return-path: Received: from mail.kernel.org ([198.145.29.99]:41650 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725821AbgFCW7d (ORCPT ); Wed, 3 Jun 2020 18:59:33 -0400 In-Reply-To: <20200603155549.e041363450869eaae4c7f05b@linux-foundation.org> Sender: mm-commits-owner@vger.kernel.org List-Id: mm-commits@vger.kernel.org To: akpm@linux-foundation.org, alex.williamson@redhat.com, alexander.h.duyck@linux.intel.com, corbet@lwn.net, dan.j.williams@intel.com, daniel.m.jordan@oracle.com, dave.hansen@linux.intel.com, david@redhat.com, elliott@hpe.com, herbert@gondor.apana.org.au, jgg@ziepe.ca, josh@joshtriplett.org, ktkhai@virtuozzo.com, linux-mm@kvack.org, mhocko@kernel.org, mm-commits@vger.kernel.org, pasha.tatashin@soleen.com, pavel@ucw.cz, peterz@infradead.org, rdunlap@infradead.org, shile.zhang@linux.alibaba.com, steffen.klassert@secunet.com, steven.sistare@oracle.com, tj@kernel.org, torvalds@linux-foundation.org, ziy@nvidia.com From: Daniel Jordan Subject: padata: remove exit routine Patch series "padata: parallelize deferred page init", v3. Deferred struct page init is a bottleneck in kernel boot--the biggest for us and probably others. Optimizing it maximizes availability for large-memory systems and allows spinning up short-lived VMs as needed without having to leave them running. It also benefits bare metal machines hosting VMs that are sensitive to downtime. In projects such as VMM Fast Restart[1], where guest state is preserved across kexec reboot, it helps prevent application and network timeouts in the guests. So, multithread deferred init to take full advantage of system memory bandwidth. Extend padata, a framework that handles many parallel singlethreaded jobs, to handle multithreaded jobs as well by adding support for splitting up the work evenly, specifying a minimum amount of work that's appropriate for one helper thread to do, load balancing between helpers, and coordinating them. More documentation in patches 4 and 8. This series is the first step in a project to address other memory proportional bottlenecks in the kernel such as pmem struct page init, vfio page pinning, hugetlb fallocate, and munmap. Deferred page init doesn't require concurrency limits, resource control, or priority adjustments like these other users will because it happens during boot when the system is otherwise idle and waiting for page init to finish. This has been run on a variety of x86 systems and speeds up kernel boot by 4% to 49%, saving up to 1.6 out of 4 seconds. Patch 6 has more numbers. This patch (of 8): padata_driver_exit() is unnecessary because padata isn't built as a module and doesn't exit. padata's init routine will soon allocate memory, so getting rid of the exit function now avoids pointless code to free it. Link: http://lkml.kernel.org/r/20200527173608.2885243-1-daniel.m.jordan@oracle.com Link: http://lkml.kernel.org/r/20200527173608.2885243-2-daniel.m.jordan@oracle.com Signed-off-by: Daniel Jordan Tested-by: Josh Triplett Cc: Alexander Duyck Cc: Alex Williamson Cc: Dan Williams Cc: Dave Hansen Cc: David Hildenbrand Cc: Herbert Xu Cc: Jason Gunthorpe Cc: Jonathan Corbet Cc: Kirill Tkhai Cc: Michal Hocko Cc: Pavel Machek Cc: Pavel Tatashin Cc: Peter Zijlstra Cc: Randy Dunlap Cc: Robert Elliott Cc: Shile Zhang Cc: Steffen Klassert Cc: Steven Sistare Cc: Tejun Heo Cc: Zi Yan Signed-off-by: Andrew Morton --- kernel/padata.c | 6 ------ 1 file changed, 6 deletions(-) --- a/kernel/padata.c~padata-remove-exit-routine +++ a/kernel/padata.c @@ -1074,10 +1074,4 @@ static __init int padata_driver_init(voi } module_init(padata_driver_init); -static __exit void padata_driver_exit(void) -{ - cpuhp_remove_multi_state(CPUHP_PADATA_DEAD); - cpuhp_remove_multi_state(hp_online); -} -module_exit(padata_driver_exit); #endif _