linux-kernel - Re: vchiq: Performance regression since 5.18-rc1

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Date:   Wed, 25 May 2022 12:37:37 -0300
From:   Marcelo Tosatti <mtosatti@...hat.com>
To:     Stefan Wahren <stefan.wahren@...e.com>
Cc:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Nicolas Saenz Julienne <nsaenzju@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        Minchan Kim <minchan@...nel.org>,
        Matthew Wilcox <willy@...radead.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Juri Lelli <juri.lelli@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Phil Elwell <phil@...pberrypi.com>, regressions@...ts.linux.dev
Subject: Re: vchiq: Performance regression since 5.18-rc1

On Wed, May 25, 2022 at 04:07:47PM +0200, Stefan Wahren wrote:
> Hi Marcelo,
> 
> Am 25.05.22 um 15:56 schrieb Marcelo Tosatti:
> > On Mon, May 23, 2022 at 09:09:07AM +0200, Sebastian Andrzej Siewior wrote:
> > > On 2022-05-22 01:22:00 [+0200], Stefan Wahren wrote:
> > > > Hi,
> > > Hi,
> > > 
> > > > while testing the staging/vc04_services/interface/vchiq_arm driver with my
> > > > Raspberry Pi 3 B+ (multi_v7_defconfig) i noticed a huge performance
> > > > regression since [ff042f4a9b050895a42cae893cc01fa2ca81b95c] mm:
> > > > lru_cache_disable: replace work queue synchronization with synchronize_rcu
> > > > 
> > > > Usually i run "vchiq_test -f 1" to see the driver is still working [1].
> > > What about
> > > 	https://lore.kernel.org/all/YmrWK%2FKoU1zrAxPI@fuller.cnet/
> > > 
> > > Sebastian
> > Stefan,
> > 
> > Can you please try the patch above ?
> 
> this was the same as Paul send. I think i need more time for investigation,
> maybe there is an issue with the application.

To clarify: they are not the same patches.

> 
> All i noticed so far is that in good case the CPU usage is around ~ 60 % and
> higher, while in bad case the CPU is almost idle. Also the issue is not
> reproducible with arm64/defconfig.
> 
> > 
> > 
> > 
> > _______________________________________________
> > linux-arm-kernel mailing list
> > linux-arm-kernel@...ts.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> 
> 

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