From: Jesse Barnes <jsbarnes@google.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "Yu Zhao" <yuzhao@google.com>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Justin Forbes" <jforbes@fedoraproject.org>,
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"Jonathan Corbet" <corbet@lwn.net>,
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"Konstantin Kharlamov" <Hi-Angel@yandex.ru>,
"Shuang Zhai" <szhai2@cs.rochester.edu>,
"Sofia Trinh" <sofia.trinh@edi.works>,
"Vaibhav Jain" <vaibhav@linux.ibm.com>
Subject: Re: [page-reclaim] Re: [PATCH v10 08/14] mm: multi-gen LRU: support page table walks
Date: Fri, 15 Apr 2022 16:24:14 -0700 [thread overview]
Message-ID: <CAJmaN=mJKAhRjDHbsLrqyK_uvuysx596jEcTwV2fwx4UOe4oow@mail.gmail.com> (raw)
In-Reply-To: <CAHk-=whneDk3Jde3J+O-fD32VjaK+fDf9+P6jgDtr2qyo0iu2w@mail.gmail.com>
On Fri, Apr 15, 2022 at 4:04 PM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> On Fri, Apr 15, 2022 at 3:58 PM Yu Zhao <yuzhao@google.com> wrote:
> >
> > BUG_ONs are harmful but problems that trigger them would be
> > presummingly less penetrating to the user base; on the other hand,
> > from my experience working with some testers (ordinary users), they
> > ignore WARN_ON_ONCEs until the kernel crashes.
>
> I don't understand your argument.
>
> First you say that VM_BUG_ON() is only for VM developers.
>
> Then you say "some testers (ordinary users) ignore WARN_ON_ONCEs until
> the kernel crashes".
>
> So which is it?
>
> VM developers, or ordinary users?
>
> Honestly, if a VM developer is ignoring a WARN_ON_ONCE() from the VM
> subsystem, I don't even know what to say.
>
> And for ordinary users, a WARN_ON_ONCE() is about a million times
> better, becasue:
>
> - the machine will hopefully continue working, so they can report the warning
>
> - even when they don't notice them, distros tend to have automated
> reporting infrastructure
>
> That's why I absolutely *DETEST* those stupid BUG_ON() cases - they
> will often kill the machine with nasty locks held, resulting in a
> completely undebuggable thing that never gets reported.
>
> Yes, you can be careful and only put BUG_ON() in places where recovery
> is possible. But even then, they have no actual _advantages_ over just
> a WARN_ON_ONCE.
Generally agreed, and not to belabor this relatively small issue, but in some
environments like cloud or managed client deployments, a crash can actually
be preferable so we can get a dump, reboot the machine, and get things going
again for the application or user, then debug offline. So having the
flexibility to
do that in those situations is helpful. And there, a full crash dump is better
than just a log report with the WARN info, since debugging may be easier with
all the kernel memory.
Jesse
next prev parent reply other threads:[~2022-04-15 23:24 UTC|newest]
Thread overview: 98+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-07 3:15 [PATCH v10 00/14] Multi-Gen LRU Framework Yu Zhao
2022-04-07 3:15 ` [PATCH v10 01/14] mm: x86, arm64: add arch_has_hw_pte_young() Yu Zhao
2022-04-07 3:15 ` [PATCH v10 02/14] mm: x86: add CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG Yu Zhao
2022-04-07 3:15 ` [PATCH v10 03/14] mm/vmscan.c: refactor shrink_node() Yu Zhao
2022-04-16 6:48 ` Miaohe Lin
2022-04-07 3:15 ` [PATCH v10 04/14] Revert "include/linux/mm_inline.h: fold __update_lru_size() into its sole caller" Yu Zhao
2022-04-16 6:50 ` Miaohe Lin
2022-04-07 3:15 ` [PATCH v10 05/14] mm: multi-gen LRU: groundwork Yu Zhao
2022-04-12 2:16 ` Andrew Morton
2022-04-12 7:06 ` Peter Zijlstra
2022-04-20 0:39 ` Yu Zhao
2022-04-20 20:07 ` Linus Torvalds
2022-04-26 22:39 ` Yu Zhao
2022-04-26 23:42 ` Andrew Morton
2022-04-27 1:18 ` Yu Zhao
2022-04-27 1:34 ` Andrew Morton
2022-04-07 3:15 ` [PATCH v10 06/14] mm: multi-gen LRU: minimal implementation Yu Zhao
2022-04-14 6:03 ` Barry Song
2022-04-14 20:36 ` Yu Zhao
2022-04-14 21:39 ` Andrew Morton
2022-04-14 22:14 ` Yu Zhao
2022-04-15 10:15 ` Barry Song
2022-04-15 20:17 ` Yu Zhao
2022-04-15 10:26 ` Barry Song
2022-04-15 20:18 ` Yu Zhao
[not found] ` <71af92d2-0777-c318-67fb-8f7d52c800bb@huawei.com>
2022-04-14 20:53 ` Yu Zhao
2022-04-15 2:23 ` Chen Wandun
2022-04-15 5:25 ` Yu Zhao
2022-04-15 6:31 ` Chen Wandun
2022-04-15 6:44 ` Yu Zhao
2022-04-15 9:27 ` Chen Wandun
2022-04-18 9:58 ` Barry Song
2022-04-19 0:53 ` Yu Zhao
2022-04-19 4:25 ` Barry Song
2022-04-19 4:36 ` Barry Song
2022-04-19 22:25 ` Yu Zhao
2022-04-19 22:20 ` Yu Zhao
2022-04-07 3:15 ` [PATCH v10 07/14] mm: multi-gen LRU: exploit locality in rmap Yu Zhao
2022-04-27 4:32 ` Aneesh Kumar K.V
2022-04-27 4:38 ` Yu Zhao
2022-04-27 5:31 ` Aneesh Kumar K V
2022-04-27 6:00 ` Yu Zhao
2022-04-07 3:15 ` [PATCH v10 08/14] mm: multi-gen LRU: support page table walks Yu Zhao
2022-04-12 2:16 ` Andrew Morton
2022-04-12 7:10 ` Peter Zijlstra
2022-04-15 5:30 ` Yu Zhao
2022-04-15 1:14 ` Yu Zhao
2022-04-15 1:56 ` Andrew Morton
2022-04-15 6:25 ` Yu Zhao
2022-04-15 19:15 ` Andrew Morton
2022-04-15 20:11 ` Yu Zhao
2022-04-15 21:32 ` Andrew Morton
2022-04-15 21:36 ` Linus Torvalds
2022-04-15 22:57 ` Yu Zhao
2022-04-15 23:03 ` Linus Torvalds
2022-04-15 23:24 ` Jesse Barnes [this message]
2022-04-15 23:31 ` [page-reclaim] " Matthew Wilcox
2022-04-15 23:37 ` Jesse Barnes
2022-04-15 23:49 ` Yu Zhao
2022-04-16 16:32 ` Justin Forbes
2022-04-19 22:32 ` Yu Zhao
2022-04-29 14:10 ` zhong jiang
2022-04-30 8:34 ` Yu Zhao
2022-04-07 3:15 ` [PATCH v10 09/14] mm: multi-gen LRU: optimize multiple memcgs Yu Zhao
2022-04-07 3:15 ` [PATCH v10 10/14] mm: multi-gen LRU: kill switch Yu Zhao
2022-04-12 2:16 ` Andrew Morton
2022-04-26 20:57 ` Yu Zhao
2022-04-26 22:22 ` Andrew Morton
2022-04-27 1:11 ` Yu Zhao
2022-04-07 3:15 ` [PATCH v10 11/14] mm: multi-gen LRU: thrashing prevention Yu Zhao
2022-04-07 3:15 ` [PATCH v10 12/14] mm: multi-gen LRU: debugfs interface Yu Zhao
2022-04-12 2:16 ` Andrew Morton
2022-04-16 0:03 ` Yu Zhao
2022-04-16 4:20 ` Andrew Morton
2022-04-26 6:59 ` Yu Zhao
2022-04-26 21:30 ` Andrew Morton
2022-04-26 22:15 ` Yu Zhao
2022-04-07 3:15 ` [PATCH v10 13/14] mm: multi-gen LRU: admin guide Yu Zhao
2022-04-07 12:41 ` Bagas Sanjaya
2022-04-07 12:51 ` Jonathan Corbet
2022-04-12 2:16 ` Andrew Morton
2022-04-16 2:22 ` Yu Zhao
2022-04-07 3:15 ` [PATCH v10 14/14] mm: multi-gen LRU: design doc Yu Zhao
2022-04-07 11:39 ` Huang Shijie
2022-04-07 12:41 ` Bagas Sanjaya
2022-04-07 12:52 ` Jonathan Corbet
2022-04-08 4:48 ` Bagas Sanjaya
2022-04-12 2:16 ` Andrew Morton
2022-04-26 7:42 ` Yu Zhao
2022-04-07 3:24 ` [PATCH v10 00/14] Multi-Gen LRU Framework Yu Zhao
2022-04-07 8:31 ` Stephen Rothwell
2022-04-07 9:08 ` Yu Zhao
2022-04-07 9:41 ` Yu Zhao
2022-04-07 12:13 ` Stephen Rothwell
2022-04-08 2:08 ` Yu Zhao
2022-04-12 2:15 ` Andrew Morton
2022-04-14 5:06 ` Andrew Morton
2022-04-20 0:50 ` Yu Zhao
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