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Message-ID: <e0402350-687e-14b6-2e30-4b459afa9afb@i2se.com>
Date:   Wed, 25 May 2022 16:07:47 +0200
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Subject: Re: vchiq: Performance regression since 5.18-rc1
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To:     Marcelo Tosatti <mtosatti@redhat.com>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Nicolas Saenz Julienne <nsaenzju@redhat.com>,
        Borislav Petkov <bp@alien8.de>,
        Minchan Kim <minchan@kernel.org>,
        Matthew Wilcox <willy@infradead.org>,
        Mel Gorman <mgorman@techsingularity.net>,
        Juri Lelli <juri.lelli@redhat.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        "Paul E. McKenney" <paulmck@kernel.org>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Phil Elwell <phil@raspberrypi.com>, regressions@lists.linux.dev
References: <77d6d498-7dd9-03eb-60f2-d7e682bb1b20@i2se.com>
 <YoszE8lQ9VcofLtX@linutronix.de> <Yo41ggMvkI1B9TeM@fuller.cnet>
From:   Stefan Wahren <stefan.wahren@i2se.com>
In-Reply-To: <Yo41ggMvkI1B9TeM@fuller.cnet>
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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.

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.

>
>
>
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