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From: Vlastimil Babka <vbabka@suse.cz>
To: Maxim Levitsky <mlevitsk@redhat.com>,
	Jiri Slaby <jirislaby@kernel.org>,
	Pedro Falcato <pedro.falcato@gmail.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
	kvm@vger.kernel.org, Andrew Morton <akpm@linux-foundation.org>,
	mm <linux-mm@kvack.org>,
	yuzhao@google.com, Michal Hocko <MHocko@suse.com>,
	shy828301@gmail.com, Mel Gorman <mgorman@techsingularity.net>
Subject: Re: Stalls in qemu with host running 6.1 (everything stuck at mmap_read_lock())
Date: Thu, 12 Jan 2023 11:35:26 +0100	[thread overview]
Message-ID: <1d278b52-5c75-1f95-adf8-3e9c699cf6ca@suse.cz> (raw)
In-Reply-To: <6d989ca2330748ed682c81fc5f43e054a70e70a8.camel@redhat.com>

On 1/12/23 11:31, Maxim Levitsky wrote:
> On Thu, 2023-01-12 at 07:07 +0100, Jiri Slaby wrote:
>> 
>> I have rebooted to a fresh kernel which 1) have lockdep enabled, and 2) 
>> I have debuginfo for. So next time this happens, I can print held locks 
>> and dump a kcore (kdump is set up).
>> 
>> regards,
> 
> It is also possible that I noticed something like that on 6.1:
> 
> For me it happens when my system (also no swap, 96G out which 48 are permanetly reserved as 1G hugepages,
> and this happens with VMs which don't use this hugepage reserve) 
> is somewhat low on memory and qemu tries to lock all memory (I use -overcommit mem-lock=on)
> 
> Like it usually happens when I start 32 GB VM while having lot of stuff open in background, but
> still not nearly close to 16GB.
> As a workaround I lowered the reserved area to 32G.
> 
> I also see indication that things like htop or even opening a new shell hang quite hard.
> 
> What almost instantly helps is 'echo 3 | sudo tee /proc/sys/vm/drop_caches'
> e.g that makes the VM start booting, and unlocks everything.

Note it's possible that temporary+recoverable things like that have a
different cause caused by compaction caught in a loop, as discussed here:

https://lore.kernel.org/all/a032e3bf-8470-095a-2262-791f5678e590@suse.cz/

> Best regards,
> 	Maxim Levitsky
> 


  reply	other threads:[~2023-01-12 10:42 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-01-11  8:00 Stalls in qemu with host running 6.1 (everything stuck at mmap_read_lock()) Jiri Slaby
2023-01-11  8:23 ` Vlastimil Babka
2023-01-11  8:31 ` Michal Hocko
2023-01-11  9:21 ` Linux kernel regression tracking (#adding)
2023-01-19 14:58   ` Vlastimil Babka
2023-01-11 22:50 ` Paolo Bonzini
2023-01-12  0:37 ` Pedro Falcato
2023-01-12  6:07   ` Jiri Slaby
2023-01-12 10:31     ` Maxim Levitsky
2023-01-12 10:35       ` Vlastimil Babka [this message]
2023-01-12 15:43     ` Jiri Slaby
2023-01-12 16:57       ` Jiri Slaby
2023-01-13 17:14         ` Liam Howlett
2023-01-12  8:23   ` Yu Zhao
2023-01-13 17:27     ` Liam Howlett

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