From: Pavel Machek <pavel@ucw.cz>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: kernel list <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@osdl.org>,
mhocko@suse.cz, "linux-mm@kvack.org" <linux-mm@kvack.org>
Subject: Re: 5.7-rc0: kswapd eats cpu during a disk test?!
Date: Sat, 13 Jun 2020 01:05:52 +0200 [thread overview]
Message-ID: <20200612230552.GA3593@amd> (raw)
In-Reply-To: <20200612224532.GA24103@amd>
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Hi!
> > +CC linux-mm
> >
> > On 5/31/20 12:34 PM, Pavel Machek wrote:
> > > Hi!
> > >
> > > This is simple cat /dev/sda > /dev/zero... on thinkpad x60 (x86-32),
> > > with spinning rust.
> > >
> > > PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
> > > 1000 root 20 0 0 0 0 R 53.3 0.0 57:34.93 kswapd0
> > > 27897 root 20 0 6976 580 536 R 44.5 0.0 1:44.53 cat
> > >
> > > It keeps both CPUs busy... and I don't think that's right.
> >
> > Does an older kernel behave differently here?
>
> Let me try on x220 (x86-64, first):
>
> 737 root 20 0 5404 744 680 R 31.2 0.0 0:09.98 cat
> 1024 root 20 0 0 0 0 S 21.4 0.0 165:22.68 kswapd0
>
> That was with ssd, result with spinning rust is similar:
>
> 859 root 20 0 5404 740 672 D 21.1 0.0 0:03.33 cat
> 1024 root 20 0 0 0 0 R 11.8 0.0 165:33.07 kswapd0
>
> 5.7-rc1+ kernel.
>
> Performance of spinning rust is down, too, on x60:
>
> pavel@amd:~/misc/hw/hdd1t$ sudo ddrescue --force /dev/sda1 /dev/null
> GNU ddrescue 1.19
> Press Ctrl-C to interrupt
> rescued: 2147 MB, errsize: 0 B, current rate: 3080 kB/s
> ipos: 2147 MB, errors: 0, average rate: 5382 kB/s
> opos: 2147 MB, run time: 6.65 m, successful read:
> 0 s ago
> Finished
> pavel@amd:~/misc/hw/hdd1t$ uname -a
> Linux amd 5.7.0-next-20200611+ #123 SMP PREEMPT Thu Jun 11
> 15:41:22 CEST 2020 i686 GNU/Linux
>
> And there's something clearly wrong here:
>
> 966 root 20 0 0 0 0 R 94.4 0.0 8:18.82 kswapd0
> 23933 root 20 0 4612 1112 1028 D 80.6 0.0 0:26.40 ddrescue
>
Same x60 under older kernel:
pavel@amd:/data/fast/pavel$ sudo ddrescue --force /dev/sda4 /dev/null
GNU ddrescue 1.19
Press Ctrl-C to interrupt
rescued: 6593 MB, errsize: 0 B, current rate: 60424 kB/s
ipos: 6593 MB, errors: 0, average rate: 95563 kB/s
3539 root 20 0 4616 1136 1048 D 21.4 0.0 0:15.63 ddrescue
865 root 20 0 0 0 0 S 6.9 0.0 0:04.91 kswapd0
Linux amd 4.6.0+ #172 SMP Sun Aug 14 11:25:34 CEST 2016 i686 GNU/Linux
These are more reasonable numbers.
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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next prev parent reply other threads:[~2020-06-12 23:05 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20200531103431.GA28429@amd>
2020-06-01 8:55 ` Vlastimil Babka
2020-06-12 22:45 ` Pavel Machek
2020-06-12 23:05 ` Pavel Machek [this message]
2020-06-13 4:47 ` Hillf Danton
2020-06-13 6:48 ` Pavel Machek
2020-06-13 9:43 ` Hillf Danton
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