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Re: fast path cycle muncher (vmstat: make vmstat_updater deferrable again and shut down on idle)

From Mike Galbraith <umgwanakikbuti@gmail.com>
Newsgroups linux.kernel
Subject Re: fast path cycle muncher (vmstat: make vmstat_updater deferrable again and shut down on idle)
Date 2016-01-24 06:40 +0100
Message-ID <qUlz3-bV-7@gated-at.bofh.it> (permalink)
References (11 earlier) <qTN4n-6Dx-31@gated-at.bofh.it> <qU9ey-5ik-15@gated-at.bofh.it> <qUgSJ-5ds-9@gated-at.bofh.it> <qUiUy-6x1-7@gated-at.bofh.it> <qUjQB-7iY-3@gated-at.bofh.it>
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On Sat, 2016-01-23 at 21:46 -0600, Christoph Lameter wrote:
> On Sun, 24 Jan 2016, Mike Galbraith wrote:
> 
> > By switching cross-core, I'm referring to scheduling of communicating
> > tasks.
> 
> ??? Its cancelling a work request. That is a "communicating task"?

No no no, pipe-test is two tasks playing ping-pong via a pipe.  They
are about as synchronous as it gets, so each task goes idle at high
frequency.  Idle is fastpath.

> > Here's the sleeping lock for -rt:
> > 
> > [    2.279582] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.5.0-rt3 #7
> > [    2.280444] Hardware name: MEDION MS-7848/MS-7848, BIOS M7848W08.20C 09/23/2013
> > [    2.281316]  ffff88040b00d640 ffff88040b01fe10 ffffffff812d20e2 0000000000000000
> > [    2.282202]  ffff88040b01fe30 ffffffff81081095 ffff88041ec4cee0 ffff88041ec501e0
> > [    2.283073]  ffff88040b01fe48 ffffffff815ff910 ffff88041ec4cee0 ffff88040b01fe88
> > [    2.283941] Call Trace:
> > [    2.284797]  [] dump_stack+0x49/0x67
> > [    2.285658]  [] ___might_sleep+0xf5/0x180
> > [    2.286521]  [] rt_spin_lock+0x20/0x50
> > [    2.287382]  [] try_to_grab_pending+0x69/0x240
> > [    2.288239]  [] cancel_delayed_work+0x26/0xe0
> 
> OMG cancelling a work request causes a sleeping lock to be taken?

Yup.  In -rt, spinlocks that are not raw are transformed into rtmutex.

	-Mike

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Re: mm, vmstat: kernel BUG at mm/vmstat.c:1408! Michal Hocko <mhocko@kernel.org> - 2016-01-20 15:40 +0100
  Re: mm, vmstat: kernel BUG at mm/vmstat.c:1408! Sasha Levin <sasha.levin@oracle.com> - 2016-01-20 16:00 +0100
    Re: mm, vmstat: kernel BUG at mm/vmstat.c:1408! Michal Hocko <mhocko@kernel.org> - 2016-01-20 16:20 +0100
      Re: mm, vmstat: kernel BUG at mm/vmstat.c:1408! Christoph Lameter <cl@linux.com> - 2016-01-20 16:30 +0100
        Re: mm, vmstat: kernel BUG at mm/vmstat.c:1408! Sasha Levin <sasha.levin@oracle.com> - 2016-01-20 17:00 +0100
          Re: mm, vmstat: kernel BUG at mm/vmstat.c:1408! Christoph Lameter <cl@linux.com> - 2016-01-20 17:00 +0100
            Re: mm, vmstat: kernel BUG at mm/vmstat.c:1408! Michal Hocko <mhocko@kernel.org> - 2016-01-20 22:30 +0100
              Re: mm, vmstat: kernel BUG at mm/vmstat.c:1408! Christoph Lameter <cl@linux.com> - 2016-01-20 23:00 +0100
                Re: mm, vmstat: kernel BUG at mm/vmstat.c:1408! Michal Hocko <mhocko@kernel.org> - 2016-01-21 09:30 +0100
                Re: mm, vmstat: kernel BUG at mm/vmstat.c:1408! Christoph Lameter <cl@linux.com> - 2016-01-21 16:50 +0100
                Re: mm, vmstat: kernel BUG at mm/vmstat.c:1408! Michal Hocko <mhocko@kernel.org> - 2016-01-21 18:00 +0100
                Re: mm, vmstat: kernel BUG at mm/vmstat.c:1408! Christoph Lameter <cl@linux.com> - 2016-01-21 18:40 +0100
                Re: mm, vmstat: kernel BUG at mm/vmstat.c:1408! Shiraz Hashim <shiraz.linux.kernel@gmail.com> - 2016-01-22 12:10 +0100
                Re: mm, vmstat: kernel BUG at mm/vmstat.c:1408! Michal Hocko <mhocko@kernel.org> - 2016-01-22 15:10 +0100
                Re: mm, vmstat: kernel BUG at mm/vmstat.c:1408! Christoph Lameter <cl@linux.com> - 2016-01-22 17:10 +0100
                Re: mm, vmstat: kernel BUG at mm/vmstat.c:1408! Michal Hocko <mhocko@kernel.org> - 2016-01-22 17:20 +0100
                Re: mm, vmstat: kernel BUG at mm/vmstat.c:1408! Christoph Lameter <cl@linux.com> - 2016-01-22 17:50 +0100
                Re: mm, vmstat: kernel BUG at mm/vmstat.c:1408! Michal Hocko <mhocko@kernel.org> - 2016-01-22 18:20 +0100
                fast path cycle muncher (vmstat: make vmstat_updater deferrable  again and shut down on idle) Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-01-23 17:30 +0100
                Re: fast path cycle muncher (vmstat: make vmstat_updater deferrable  again and shut down on idle) Christoph Lameter <cl@linux.com> - 2016-01-24 01:40 +0100
                Re: fast path cycle muncher (vmstat: make vmstat_updater deferrable  again and shut down on idle) Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-01-24 03:50 +0100
                Re: fast path cycle muncher (vmstat: make vmstat_updater deferrable  again and shut down on idle) Christoph Lameter <cl@linux.com> - 2016-01-24 04:50 +0100
                Re: fast path cycle muncher (vmstat: make vmstat_updater deferrable  again and shut down on idle) Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-01-24 06:40 +0100
                Re: fast path cycle muncher (vmstat: make vmstat_updater deferrable  again and shut down on idle) Michal Hocko <mhocko@kernel.org> - 2016-01-25 18:50 +0100
                Re: fast path cycle muncher (vmstat: make vmstat_updater deferrable  again and shut down on idle) Christoph Lameter <cl@linux.com> - 2016-01-25 19:10 +0100
                Re: fast path cycle muncher (vmstat: make vmstat_updater deferrable  again and shut down on idle) Michal Hocko <mhocko@kernel.org> - 2016-01-25 21:20 +0100
                Re: fast path cycle muncher (vmstat: make vmstat_updater deferrable  again and shut down on idle) Christoph Lameter <cl@linux.com> - 2016-01-26 17:30 +0100
                Re: fast path cycle muncher (vmstat: make vmstat_updater deferrable  again and shut down on idle) Christoph Lameter <cl@linux.com> - 2016-01-26 19:40 +0100
                Re: fast path cycle muncher (vmstat: make vmstat_updater deferrable  again and shut down on idle) Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-01-26 19:50 +0100
                Re: fast path cycle muncher (vmstat: make vmstat_updater deferrable  again and shut down on idle) Christoph Lameter <cl@linux.com> - 2016-01-26 20:30 +0100
                Re: fast path cycle muncher (vmstat: make vmstat_updater deferrable  again and shut down on idle) Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-01-27 04:20 +0100
                Re: fast path cycle muncher (vmstat: make vmstat_updater deferrable  again and shut down on idle) Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-01-27 05:20 +0100
                Re: fast path cycle muncher (vmstat: make vmstat_updater deferrable  again and shut down on idle) Christoph Lameter <cl@linux.com> - 2016-01-27 17:30 +0100
                Re: fast path cycle muncher (vmstat: make vmstat_updater deferrable  again and shut down on idle) Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-01-26 19:40 +0100
                Re: fast path cycle muncher (vmstat: make vmstat_updater deferrable  again and shut down on idle) Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-01-26 03:20 +0100
                Re: fast path cycle muncher (vmstat: make vmstat_updater deferrable  again and shut down on idle) Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-01-26 03:30 +0100
                Re: fast path cycle muncher (vmstat: make vmstat_updater deferrable  again and shut down on idle) Christoph Lameter <cl@linux.com> - 2016-01-26 17:30 +0100
                Re: fast path cycle muncher (vmstat: make vmstat_updater deferrable  again and shut down on idle) Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-01-26 18:40 +0100
                Re: fast path cycle muncher (vmstat: make vmstat_updater deferrable  again and shut down on idle) Christoph Lameter <cl@linux.com> - 2016-01-26 19:20 +0100
                Re: fast path cycle muncher (vmstat: make vmstat_updater deferrable  again and shut down on idle) Christoph Lameter <cl@linux.com> - 2016-01-26 17:30 +0100
                Re: fast path cycle muncher (vmstat: make vmstat_updater deferrable  again and shut down on idle) Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-01-26 18:10 +0100
                Re: fast path cycle muncher (vmstat: make vmstat_updater deferrable  again and shut down on idle) Christoph Lameter <cl@linux.com> - 2016-01-26 19:30 +0100
                Re: fast path cycle muncher (vmstat: make vmstat_updater deferrable  again and shut down on idle) Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-01-26 20:10 +0100
                Re: fast path cycle muncher (vmstat: make vmstat_updater deferrable  again and shut down on idle) Christoph Lameter <cl@linux.com> - 2016-01-26 20:30 +0100
                [PATCH] mm, vmstat: make quiet_vmstat lighter (was: Re: fast path  cycle muncher (vmstat: make vmstat_updater deferrable) again and shut down  on idle) Michal Hocko <mhocko@kernel.org> - 2016-01-27 17:50 +0100
                Re: [PATCH] mm, vmstat: make quiet_vmstat lighter (was: Re: fast  path cycle muncher (vmstat: make vmstat_updater deferrable) again and shut  down on idle) Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-01-27 18:10 +0100
                Re: [PATCH] mm, vmstat: make quiet_vmstat lighter (was: Re: fast  path cycle muncher (vmstat: make vmstat_updater deferrable) again and shut  down on idle) Christoph Lameter <cl@linux.com> - 2016-01-27 19:30 +0100
                Re: mm, vmstat: kernel BUG at mm/vmstat.c:1408! Linus Torvalds <torvalds@linux-foundation.org> - 2016-01-24 18:00 +0100
  Re: mm, vmstat: kernel BUG at mm/vmstat.c:1408! Christoph Lameter <cl@linux.com> - 2016-01-20 16:20 +0100
    Re: mm, vmstat: kernel BUG at mm/vmstat.c:1408! Michal Hocko <mhocko@kernel.org> - 2016-01-20 16:30 +0100

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