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From: Byungchul Park <byungchul.park@lge.com>
To: Theodore Ts'o <tytso@mit.edu>
Cc: tj@kernel.org, torvalds@linux-foundation.org,
	damien.lemoal@opensource.wdc.com, linux-ide@vger.kernel.org,
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	melissa.srw@gmail.com, hamohammed.sa@gmail.com,
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Subject: Re: [REPORT] syscall reboot + umh + firmware fallback
Date: Mon, 23 May 2022 10:10:45 +0900	[thread overview]
Message-ID: <20220523011045.GA16721@X58A-UD3R> (raw)
In-Reply-To: <Yn0SHhnhB8fyd0jq@mit.edu>

On Thu, May 12, 2022 at 09:56:46AM -0400, Theodore Ts'o wrote:
> On Thu, May 12, 2022 at 08:18:24PM +0900, Byungchul Park wrote:
> > I have a question about this one. Yes, it would never been stuck thanks
> > to timeout. However, IIUC, timeouts are not supposed to expire in normal
> > cases. So I thought a timeout expiration means not a normal case so need
> > to inform it in terms of dependency so as to prevent further expiraton.
> > That's why I have been trying to track even timeout'ed APIs.
> 
> As I beleive I've already pointed out to you previously in ext4 and
> ocfs2, the jbd2 timeout every five seconds happens **all** the time
> while the file system is mounted.  Commits more frequently than five
> seconds is the exception case, at least for desktops/laptop workloads.

Thanks, Ted. It's easy to stop tracking APIs with timeout. I've been
just afraid that the cases that we want to suppress anyway will be
skipped.

However, I should stop it if it produces too many false alarms.

> We *don't* get to the timeout only when a userspace process calls
> fsync(2), or if the journal was incorrectly sized by the system
> administrator so that it's too small, and the workload has so many
> file system mutations that we have to prematurely close the
> transaction ahead of the 5 second timeout.

Yeah... It's how journaling works. Thanks.

> > Do you think DEPT shouldn't track timeout APIs? If I was wrong, I
> > shouldn't track the timeout APIs any more.
> 
> DEPT tracking timeouts will cause false positives in at least some
> cases.  At the very least, there needs to be an easy way to suppress
> these false positives on a per wait/mutex/spinlock basis.

The easy way is to stop tracking those that are along with timeout until
DEPT starts to consider waits/events by timeout functionality itself.

Thanks.

	Byungchul
> 
>       	       	    	     	      	   	 - Ted

  reply	other threads:[~2022-05-23  1:12 UTC|newest]

Thread overview: 52+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-05-04  8:17 [PATCH RFC v6 00/21] DEPT(Dependency Tracker) Byungchul Park
2022-05-04  8:17 ` [PATCH RFC v6 01/21] llist: Move llist_{head,node} definition to types.h Byungchul Park
2022-05-04  8:17 ` [PATCH RFC v6 02/21] dept: Implement Dept(Dependency Tracker) Byungchul Park
2022-05-21  3:24   ` Hyeonggon Yoo
2022-05-04  8:17 ` [PATCH RFC v6 03/21] dept: Apply Dept to spinlock Byungchul Park
2022-05-04  8:17 ` [PATCH RFC v6 04/21] dept: Apply Dept to mutex families Byungchul Park
2022-05-04  8:17 ` [PATCH RFC v6 05/21] dept: Apply Dept to rwlock Byungchul Park
2022-05-04  8:17 ` [PATCH RFC v6 06/21] dept: Apply Dept to wait_for_completion()/complete() Byungchul Park
2022-05-04  8:17 ` [PATCH RFC v6 07/21] dept: Apply Dept to seqlock Byungchul Park
2022-05-21  5:25   ` Hyeonggon Yoo
2022-05-24  6:00     ` Byungchul Park
2022-05-04  8:17 ` [PATCH RFC v6 08/21] dept: Apply Dept to rwsem Byungchul Park
2022-05-04  8:17 ` [PATCH RFC v6 09/21] dept: Add proc knobs to show stats and dependency graph Byungchul Park
2022-05-04  8:17 ` [PATCH RFC v6 10/21] dept: Introduce split map concept and new APIs for them Byungchul Park
2022-05-04  8:17 ` [PATCH RFC v6 11/21] dept: Apply Dept to wait/event of PG_{locked,writeback} Byungchul Park
2022-05-04  8:17 ` [PATCH RFC v6 12/21] dept: Apply SDT to swait Byungchul Park
2022-05-04  8:17 ` [PATCH RFC v6 13/21] dept: Apply SDT to wait(waitqueue) Byungchul Park
2022-05-04  8:17 ` [PATCH RFC v6 14/21] locking/lockdep, cpu/hotplus: Use a weaker annotation in AP thread Byungchul Park
2022-05-04  8:17 ` [PATCH RFC v6 15/21] dept: Distinguish each syscall context from another Byungchul Park
2022-05-04  8:17 ` [PATCH RFC v6 16/21] dept: Distinguish each work " Byungchul Park
2022-05-04 11:23   ` Sergey Shtylyov
2022-05-04  8:17 ` [PATCH RFC v6 17/21] dept: Disable Dept within the wait_bit layer by default Byungchul Park
2022-05-04  8:17 ` [PATCH RFC v6 18/21] dept: Disable Dept on struct crypto_larval's completion for now Byungchul Park
2022-05-04  8:17 ` [PATCH RFC v6 19/21] dept: Differentiate onstack maps from others of different tasks in class Byungchul Park
2022-05-04  8:17 ` [PATCH RFC v6 20/21] dept: Do not add dependencies between events within scheduler and sleeps Byungchul Park
2022-05-04  8:17 ` [PATCH RFC v6 21/21] dept: Unstage wait when tagging a normal sleep wait Byungchul Park
2022-05-04 18:17 ` [PATCH RFC v6 00/21] DEPT(Dependency Tracker) Linus Torvalds
2022-05-06  0:11   ` Byungchul Park
2022-05-07  7:20     ` Hyeonggon Yoo
2022-05-09  0:16       ` Byungchul Park
2022-05-09 20:47         ` Steven Rostedt
2022-05-09 23:38           ` Byungchul Park
2022-05-10 14:12             ` Steven Rostedt
2022-05-10 23:26               ` Byungchul Park
2022-05-10 11:18         ` Hyeonggon Yoo
2022-05-10 23:39           ` Byungchul Park
2022-05-11 10:04             ` Hyeonggon Yoo
2022-05-19 10:11               ` Catalin Marinas
2022-05-23  2:43                 ` Byungchul Park
2022-05-09  1:22   ` Byungchul Park
2022-05-09 21:05 ` Theodore Ts'o
2022-05-09 22:28   ` Theodore Ts'o
2022-05-10  0:32     ` Byungchul Park
2022-05-10  1:32       ` Theodore Ts'o
2022-05-10  5:37         ` Byungchul Park
2022-05-11  1:16           ` Byungchul Park
2022-05-12  5:25 ` [REPORT] syscall reboot + umh + firmware fallback Byungchul Park
2022-05-12  9:15   ` Tejun Heo
2022-05-12 11:18     ` Byungchul Park
2022-05-12 13:56       ` Theodore Ts'o
2022-05-23  1:10         ` Byungchul Park [this message]
2022-05-12 16:41       ` Tejun Heo

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