From: Waiman Long <longman@redhat.com>
To: Qian Cai <cai@lca.pw>, Peter Zijlstra <peterz@infradead.org>,
Will Deacon <will@kernel.org>, Ingo Molnar <mingo@redhat.com>
Cc: David Howells <dhowells@redhat.com>,
Alexander Viro <viro@ZenIV.linux.org.uk>,
linux-fsdevel@vger.kernel.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: "BUG: MAX_LOCKDEP_ENTRIES too low" with 6979 "&type->s_umount_key"
Date: Sat, 16 May 2020 21:15:55 -0400 [thread overview]
Message-ID: <e8c6d3af-3045-0a37-5e9e-bfd60c09f97d@redhat.com> (raw)
In-Reply-To: <F430E503-F8E9-41B6-B23E-D350FD73359B@lca.pw>
On 5/15/20 1:21 AM, Qian Cai wrote:
> Lockdep is screwed here in next-20200514 due to "BUG: MAX_LOCKDEP_ENTRIES too low". One of the traces below pointed to this linux-next commit,
>
> 8c8e824d4ef0 watch_queue: Introduce a non-repeating system-unique superblock ID
>
> which was accidentally just showed up in next-20200514 along with,
>
> 46896d79c514 watch_queue: Add superblock notifications
>
> I did have here,
>
> CONFIG_SB_NOTIFICATIONS=y
> CONFIG_MOUNT_NOTIFICATIONS=y
> CONFIG_FSINFO=y
>
> While MAX_LOCKDEP_ENTRIES is 32768, I noticed there is one type of lock had a lot along,
>
> # grep 'type->s_umount_key’ /proc/lockdep_chains | wc -l
> 6979
The lock_list table entries are for tracking a lock's forward and
backward dependencies. The lockdep_chains isn't the right lockdep file
to look at. Instead, check the lockdep files for entries with the
maximum BD (backward dependency) + FD (forward dependency). That will
give you a better view of which locks are consuming most of the
lock_list entries. Also take a look at lockdep_stats for an overall view
of how much various table entries are being consumed.
Cheers,
Longman
next prev parent reply other threads:[~2020-05-17 1:16 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-15 5:21 "BUG: MAX_LOCKDEP_ENTRIES too low" with 6979 "&type->s_umount_key" Qian Cai
2020-05-17 1:15 ` Waiman Long [this message]
2020-05-17 11:12 ` Qian Cai
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