From: Steven Haigh <netwiz@crc.id.au>
To: linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: Fedora 26 / Kernel 4.11.10 - System becomes unresponsive when swapping
Date: Tue, 22 Aug 2017 21:34:12 +1000
Message-ID: <1813378.B2JPgOS4PZ@wopr.lan.crc.id.au>
In-Reply-To: <1540730.ipWl7zM1Wl@wopr.lan.crc.id.au>
References: <1540730.ipWl7zM1Wl@wopr.lan.crc.id.au>
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Hi all,

Just as a follow up - I believe I may have found a regression between kerne=
l=20
4.10.x and the newer 4.11 / 4.12 versions.

After some assistance, I have lodged this report:
	https://bugzilla.kernel.org/show_bug.cgi?id=3D196729

If anyone can assist with this, I'll be happy to reply / comment / test via=
=20
the bugzilla report to hopefully bring the issue to the surface.


On Tuesday, 18 July 2017 9:10:31 AM AEST Steven Haigh wrote:
> Hi all,
>=20
> Firstly, please CC me directly in replies due to not being subscribed.
>=20
> After a fix to glibc that fixed Unity 3D based games (Fedora ref: https://
> bugzilla.redhat.com/show_bug.cgi?id=3D1440287), I have noticed that when I
> play Cities: Skylines that the system becomes unresponsive when digging
> into swap.
>=20
> I have 10Gb of RAM in this system and run Fedora 26. If I launch Cities:
> Skylines with no swap space, things run well performance wise until I get=
 an
> OOM - and it all dies - which is expected.
>=20
> When I turn on swap to /dev/sda2 which resides on an SSD, I get complete
> system freezes while swap is being accessed.
>=20
> The first swap was after loading a saved game, then launching kmail in the
> background. This caused ~500Mb to be swapped to /dev/sda2 on an SSD. The
> system froze for about 8 minutes - barely being able to move the mouse. T=
he
> HDD LED was on constantly during the entire time.
>=20
> To hopefully rule out the above glibc issue, I started the game via jemal=
loc
> - but experienced even more severe freezes while swapping. I gave up
> waiting after 13 minutes of non-responsiveness - not even being able to
> move the mouse properly.
>=20
> During these hangs, I could typed into a Konsole window, and some of the
> typing took 3+ minutes to display on the screen (yay for buffers?).
>=20
> I have tested this with both the default vm.swappiness values, as well as
> the following:
> vm.swappiness =3D 1
> vm.min_free_kbytes =3D 32768
> vm.vfs_cache_pressure =3D 60
>=20
> I noticed that when I do eventually get screen updates, all 8 cpus (4 cor=
es
> / 2 threads) show 100% CPU usage - and kswapd is right up there in the
> process list for CPU usage. Sadly I haven't been able to capture this
> information fully yet due to said unresponsiveness.
>=20
> This seems to be a relatively new problem that I did not encounter during
> the Fedora 26 beta - but do now.
>=20
> Does anyone have any suggestions on where to start tracking this type of
> issue down?


=2D-=20
Steven Haigh

=F0=9F=93=A7 netwiz@crc.id.au       =F0=9F=92=BB http://www.crc.id.au
=F0=9F=93=9E +61 (3) 9001 6090    =F0=9F=93=B1 0412 935 897
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