From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ot1-x342.google.com (mail-ot1-x342.google.com [IPv6:2607:f8b0:4864:20::342]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 7736A21BADAB6 for ; Mon, 8 Oct 2018 14:01:16 -0700 (PDT) Received: by mail-ot1-x342.google.com with SMTP id k5so8536579ote.3 for ; Mon, 08 Oct 2018 14:01:16 -0700 (PDT) MIME-Version: 1.0 References: <20180925200551.3576.18755.stgit@localhost.localdomain> <20180925202053.3576.66039.stgit@localhost.localdomain> In-Reply-To: <20180925202053.3576.66039.stgit@localhost.localdomain> From: Dan Williams Date: Mon, 8 Oct 2018 14:01:02 -0700 Message-ID: Subject: Re: [PATCH v5 4/4] mm: Defer ZONE_DEVICE page initialization to the point where we init pgmap List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-nvdimm-bounces@lists.01.org Sender: "Linux-nvdimm" To: alexander.h.duyck@linux.intel.com Cc: Pasha Tatashin , Michal Hocko , linux-nvdimm , Dave Hansen , Linux Kernel Mailing List , Linux MM , =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , rppt@linux.vnet.ibm.com, Andrew Morton , Ingo Molnar , "Kirill A. Shutemov" List-ID: On Tue, Sep 25, 2018 at 1:29 PM Alexander Duyck wrote: > > The ZONE_DEVICE pages were being initialized in two locations. One was with > the memory_hotplug lock held and another was outside of that lock. The > problem with this is that it was nearly doubling the memory initialization > time. Instead of doing this twice, once while holding a global lock and > once without, I am opting to defer the initialization to the one outside of > the lock. This allows us to avoid serializing the overhead for memory init > and we can instead focus on per-node init times. > > One issue I encountered is that devm_memremap_pages and > hmm_devmmem_pages_create were initializing only the pgmap field the same > way. One wasn't initializing hmm_data, and the other was initializing it to > a poison value. Since this is something that is exposed to the driver in > the case of hmm I am opting for a third option and just initializing > hmm_data to 0 since this is going to be exposed to unknown third party > drivers. > > Reviewed-by: Pavel Tatashin > Signed-off-by: Alexander Duyck > --- > > v4: Moved moved memmap_init_zone_device to below memmmap_init_zone to avoid > merge conflicts with other changes in the kernel. > v5: No change This patch appears to cause a regression in the "create.sh" unit test in the ndctl test suite. I tried to reproduce on -next with: 2302f5ee215e mm: defer ZONE_DEVICE page initialization to the point where we init pgmap ...but -next does not even boot for me at that commit. Here is a warning signature that proceeds a hang with this patch applied against v4.19-rc6: percpu ref (blk_queue_usage_counter_release) <= 0 (-1530626) after switching to atomic WARNING: CPU: 24 PID: 7346 at lib/percpu-refcount.c:155 percpu_ref_switch_to_atomic_rcu+0x1f7/0x200 CPU: 24 PID: 7346 Comm: modprobe Tainted: G OE 4.19.0-rc6+ #2458 [..] RIP: 0010:percpu_ref_switch_to_atomic_rcu+0x1f7/0x200 [..] Call Trace: ? percpu_ref_reinit+0x140/0x140 rcu_process_callbacks+0x273/0x880 __do_softirq+0xd2/0x428 irq_exit+0xf6/0x100 smp_apic_timer_interrupt+0xa2/0x220 apic_timer_interrupt+0xf/0x20 RIP: 0010:lock_acquire+0xb8/0x1a0 [..] ? __put_page+0x55/0x150 ? __put_page+0x55/0x150 __put_page+0x83/0x150 ? __put_page+0x55/0x150 devm_memremap_pages_release+0x194/0x250 release_nodes+0x17c/0x2c0 device_release_driver_internal+0x1a2/0x250 driver_detach+0x3a/0x70 bus_remove_driver+0x58/0xd0 __x64_sys_delete_module+0x13f/0x200 ? trace_hardirqs_off_thunk+0x1a/0x1c do_syscall_64+0x60/0x210 entry_SYSCALL_64_after_hwframe+0x49/0xbe _______________________________________________ Linux-nvdimm mailing list Linux-nvdimm@lists.01.org https://lists.01.org/mailman/listinfo/linux-nvdimm