[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-Id: <1674119111-12759-1-git-send-email-byungchul.park@lge.com>
Date: Thu, 19 Jan 2023 18:05:11 +0900
From: Byungchul Park <byungchul.park@....com>
To: tglx@...utronix.de
Cc: linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
damien.lemoal@...nsource.wdc.com, linux-ide@...r.kernel.org,
adilger.kernel@...ger.ca, linux-ext4@...r.kernel.org,
mingo@...hat.com, peterz@...radead.org, will@...nel.org,
rostedt@...dmis.org, joel@...lfernandes.org, sashal@...nel.org,
daniel.vetter@...ll.ch, duyuyang@...il.com,
johannes.berg@...el.com, tj@...nel.org, tytso@....edu,
willy@...radead.org, david@...morbit.com, amir73il@...il.com,
gregkh@...uxfoundation.org, kernel-team@....com,
linux-mm@...ck.org, akpm@...ux-foundation.org, mhocko@...nel.org,
minchan@...nel.org, hannes@...xchg.org, vdavydov.dev@...il.com,
sj@...nel.org, jglisse@...hat.com, dennis@...nel.org, cl@...ux.com,
penberg@...nel.org, rientjes@...gle.com, vbabka@...e.cz,
ngupta@...are.org, linux-block@...r.kernel.org,
paolo.valente@...aro.org, josef@...icpanda.com,
linux-fsdevel@...r.kernel.org, viro@...iv.linux.org.uk,
jack@...e.cz, jlayton@...nel.org, dan.j.williams@...el.com,
hch@...radead.org, djwong@...nel.org,
dri-devel@...ts.freedesktop.org, rodrigosiqueiramelo@...il.com,
melissa.srw@...il.com, hamohammed.sa@...il.com,
42.hyeyoo@...il.com, chris.p.wilson@...el.com,
gwan-gyeong.mun@...el.com, max.byungchul.park@...il.com,
boqun.feng@...il.com, longman@...hat.com
Subject: Re: [PATCH RFC v7 00/23] DEPT(Dependency Tracker)
Thomas wrote:
> On Tue, Jan 17 2023 at 10:18, Boqun Feng wrote:
> > On Mon, Jan 16, 2023 at 10:00:52AM -0800, Linus Torvalds wrote:
> > > I also recall this giving a fair amount of false positives, are they all fixed?
> >
> > From the following part in the cover letter, I guess the answer is no?
> > ...
> > 6. Multiple reports are allowed.
> > 7. Deduplication control on multiple reports.
> > 8. Withstand false positives thanks to 6.
> > ...
> >
> > seems to me that the logic is since DEPT allows multiple reports so that
> > false positives are fitlerable by users?
>
> I really do not know what's so valuable about multiple reports. They
> produce a flood of information which needs to be filtered, while a
> single report ensures that the first detected issue is dumped, which
> increases the probability that it can be recorded and acted upon.
Assuming the following 2 assumptions, you are right.
Assumption 1. There will be too many reports with the multi-report
support, like all the combination of dependencies between
e.g. in-irq and irq-enabled-context.
Assumption 2. The detection is matured enough so that it barely happens
to fix false onces to see true one which is not a big deal.
However, DEPT doesn't generate all the combination of irq things as
Lockdep does so we only see a few multi-reports even with the support,
and I admit DEPT hasn't matured enough yet because fine classification
is required anyway to suppress false alarms. That's why I introduced
multi-report support at least for now. IMHO, it'd be still useful even
if it's gonna report a few true ones at once w/o false ones some day.
> Filtering out false positives is just the wrong approach. Decoding
> dependency issues from any tracker is complex enough given the nature of
> the problem, so adding the burden of filtering out issues from a stream
> of dumps is not helpful at all. It's just a marketing gag.
>
> > * Instead of introducing a brand new detector/dependency tracker,
> > could we first improve the lockdep's dependency tracker? I think
> > Byungchul also agrees that DEPT and lockdep should share the
> > same dependency tracker and the benefit of improving the
> > existing one is that we can always use the self test to catch
> > any regression. Thoughts?
>
> Ack. If the internal implementation of lockdep has shortcomings, then we
> can expand and/or replace it instead of having yet another
> infrastructure which is not even remotely as mature.
Ultimately, yes. We should expand or replace it instead of having
another ultimately.
Byungchul
>
> Thanks,
>
> tglx
Powered by blists - more mailing lists