Re: [3.13 regression] kswapd0 and ksoftirqd/0 CPU hogs

[Mikael Pettersson <mikpelinux@gmail.com>]

Mikael Pettersson writes:
 > Geert Uytterhoeven writes:
 >  > Hi Mikael,
 >  > 
 >  > On Fri, Jun 6, 2014 at 1:38 PM, Mikael Pettersson <mikpelinux@gmail.com> wrote:
 >  > > Since updating my ARAnym VMs from 3.12.16 to 3.13.11 I see kswapd0
 >  > > and ksoftirqd/0 consume inordinate amounts of CPU.  kswapd0 often
 >  > > rises to about 30-50% CPU even though RAM shouldn't be anywhere near
 >  > > depleted (768GB, a gcc bootstrap running in a screen session).
 >  > > kswapd0 tends to stay this way until I drop caches, but doing that
 >  > > doesn't always fix it.  I also sometimes see ksoftirqd/0 consume
 >  > > 5-30% CPU.
 >  > >
 >  > > Reverting to 3.12.16 completely eliminates these problems.
 >  > 
 >  > Any chance to bisect it?
 >  > 
 >  > > I haven't tested 3.14 or 3.15-rc yet.
 >  > 
 >  > Would be good to know, though, as it may have been fixed.
 >  > However, as v3.13.11 is the most recent stable version of v3.13, this may be
 >  > an elsewhere unknown and thus unfixed issue.
 > 
 > I've just started a gcc-4.8 bootstrap on 3.14.5, and then I'll try 3.15
 > if it isn't fixed in 3.14.

3.14.5 is also affected by the bug.  Dropping caches fixed kswapd0, but
instead ksoftirqd/0 jumped to 20-40%, and it refuses to calm down.