From: Byungchul Park <byungchul.park@lge.com>
To: tytso@mit.edu
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42.hyeyoo@gmail.com
Subject: Re: [PATCH RFC v6 00/21] DEPT(Dependency Tracker)
Date: Wed, 11 May 2022 10:16:37 +0900 [thread overview]
Message-ID: <20220511011637.GC18445@X58A-UD3R> (raw)
In-Reply-To: <1652161060-26531-1-git-send-email-byungchul.park@lge.com>
On Tue, May 10, 2022 at 02:37:40PM +0900, Byungchul Park wrote:
> Ted wrote:
> > On Tue, May 10, 2022 at 09:32:13AM +0900, Byungchul Park wrote:
> > > DEPT is tracking way more objects than Lockdep so it's inevitable to be
> > > slower, but let me try to make it have the similar performance to
> > > Lockdep.
> >
> > In order to eliminate some of these false positives, I suspect it's
> > going to increase the number of object classes that DEPT will need to
> > track even *more*. At which point, the cost/benefit of DEPT may get
> > called into question, especially if all of the false positives can't
> > be suppressed.
>
> Look. Let's talk in general terms. There's no way to get rid of the
> false positives all the way. It's a decision issue for *balancing*
> between considering potential cases and only real ones. Definitely,
> potential is not real. The more potential things we consider, the higher
> the chances are, that false positives appear.
>
> But yes. The advantage we'd take by detecting potential ones should be
> higher than the risk of being bothered by false ones. Do you think a
> tool is useless if it produces a few false positives? Of course, it'd
> be a problem if it's too many, but otherwise, I think it'd be a great
> tool if the advantage > the risk.
>
> Don't get me wrong here. It doesn't mean DEPT is perfect for now. The
> performance should be improved and false alarms that appear should be
> removed, of course. I'm talking about the direction.
>
> For now, there's no tool to track wait/event itself in Linux kernel -
> a subset of the functionality exists tho. DEPT is the 1st try for that
> purpose and can be a useful tool by the right direction.
>
> I know what you are concerning about. I bet it's false positives that
> are going to bother you once merged. I'll insist that DEPT shouldn't be
> used as a mandatory testing tool until considered stable enough. But
> what about ones who would take the advantage use DEPT. Why don't you
> think of folks who will take the advantage from the hints about
> dependency of synchronization esp. when their subsystem requires very
> complicated synchronization? Should a tool be useful only in a final
> testing stage? What about the usefulness during development stage?
>
> It's worth noting DEPT works with any wait/event so any lockups e.g.
> even by HW-SW interface, retry logic or the like can be detected by DEPT
> once all waits and events are tagged properly. I believe the advantage
> by that is much higher than the bad side facing false alarms. It's just
> my opinion. I'm goning to respect the majority opinion.
s/take advantage/have the benefit/g
Byungchul
next prev parent reply other threads:[~2022-05-11 1:18 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 [this message]
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
2022-05-12 16:41 ` Tejun Heo
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