On Mon, Jul 22, 2019 at 12:32:17PM -0400, Michael S. Tsirkin wrote:
> On Mon, Jul 22, 2019 at 09:25:51AM -0700, Paul E. McKenney wrote:
> > On Mon, Jul 22, 2019 at 12:13:40PM -0400, Michael S. Tsirkin wrote:
> > > On Mon, Jul 22, 2019 at 08:55:34AM -0700, Paul E. McKenney wrote:
> > > > On Mon, Jul
On Mon, Jul 22, 2019 at 09:25:51AM -0700, Paul E. McKenney wrote:
> On Mon, Jul 22, 2019 at 12:13:40PM -0400, Michael S. Tsirkin wrote:
> > On Mon, Jul 22, 2019 at 08:55:34AM -0700, Paul E. McKenney wrote:
> > > On Mon, Jul 22, 2019 at 11:47:24AM -0400, Michael S. Tsirkin wrote:
> > > > On Mon, Jul
On Mon, Jul 22, 2019 at 12:13:40PM -0400, Michael S. Tsirkin wrote:
> On Mon, Jul 22, 2019 at 08:55:34AM -0700, Paul E. McKenney wrote:
> > On Mon, Jul 22, 2019 at 11:47:24AM -0400, Michael S. Tsirkin wrote:
> > > On Mon, Jul 22, 2019 at 11:14:39AM -0400, Joel Fernandes wrote:
> > > > [snip]
> > >
On Mon, Jul 22, 2019 at 01:04:48PM -0300, Jason Gunthorpe wrote:
> On Mon, Jul 22, 2019 at 08:52:35AM -0700, Paul E. McKenney wrote:
> > So why then is there a problem?
>
> I'm not sure there is a real problem, I thought Michael was just
> asking how to design with RCU in the case where the user c
On Mon, Jul 22, 2019 at 01:04:48PM -0300, Jason Gunthorpe wrote:
> On Mon, Jul 22, 2019 at 08:52:35AM -0700, Paul E. McKenney wrote:
> > So why then is there a problem?
>
> I'm not sure there is a real problem, I thought Michael was just
> asking how to design with RCU in the case where the user c
On Mon, Jul 22, 2019 at 08:55:34AM -0700, Paul E. McKenney wrote:
> On Mon, Jul 22, 2019 at 11:47:24AM -0400, Michael S. Tsirkin wrote:
> > On Mon, Jul 22, 2019 at 11:14:39AM -0400, Joel Fernandes wrote:
> > > [snip]
> > > > > Would it make sense to have call_rcu() check to see if there are many
>
On Mon, Jul 22, 2019 at 08:52:35AM -0700, Paul E. McKenney wrote:
> So why then is there a problem?
I'm not sure there is a real problem, I thought Michael was just
asking how to design with RCU in the case where the user controls the
kfree_rcu??
Sounds like the answer is "don't worry about it" ?
On Mon, Jul 22, 2019 at 11:47:24AM -0400, Michael S. Tsirkin wrote:
> On Mon, Jul 22, 2019 at 11:14:39AM -0400, Joel Fernandes wrote:
> > [snip]
> > > > Would it make sense to have call_rcu() check to see if there are many
> > > > outstanding requests on this CPU and if so process them before
> >
On Mon, Jul 22, 2019 at 10:41:52AM -0300, Jason Gunthorpe wrote:
> On Mon, Jul 22, 2019 at 04:51:49AM -0700, Paul E. McKenney wrote:
>
> > > > > Would it make sense to have call_rcu() check to see if there are many
> > > > > outstanding requests on this CPU and if so process them before
> > > > >
On Mon, Jul 22, 2019 at 11:14:39AM -0400, Joel Fernandes wrote:
> [snip]
> > > Would it make sense to have call_rcu() check to see if there are many
> > > outstanding requests on this CPU and if so process them before returning?
> > > That would ensure that frequent callers usually ended up doing t
[snip]
> > Would it make sense to have call_rcu() check to see if there are many
> > outstanding requests on this CPU and if so process them before returning?
> > That would ensure that frequent callers usually ended up doing their
> > own processing.
Other than what Paul already mentioned about d
On Mon, Jul 22, 2019 at 04:51:49AM -0700, Paul E. McKenney wrote:
> > > > Would it make sense to have call_rcu() check to see if there are many
> > > > outstanding requests on this CPU and if so process them before
> > > > returning?
> > > > That would ensure that frequent callers usually ended u
On Mon, Jul 22, 2019 at 03:56:22AM -0400, Michael S. Tsirkin wrote:
> On Sun, Jul 21, 2019 at 12:28:41PM -0700, Paul E. McKenney wrote:
> > On Sun, Jul 21, 2019 at 01:53:23PM -0400, Michael S. Tsirkin wrote:
> > > On Sun, Jul 21, 2019 at 06:17:25AM -0700, Paul E. McKenney wrote:
> > > > On Sun, Jul
On Mon, Jul 22, 2019 at 03:52:05AM -0400, Michael S. Tsirkin wrote:
> On Sun, Jul 21, 2019 at 04:31:13PM -0700, Paul E. McKenney wrote:
> > On Sun, Jul 21, 2019 at 02:08:37PM -0700, Matthew Wilcox wrote:
> > > On Sun, Jul 21, 2019 at 06:17:25AM -0700, Paul E. McKenney wrote:
> > > > Also, the overh
On Sun, Jul 21, 2019 at 12:28:41PM -0700, Paul E. McKenney wrote:
> On Sun, Jul 21, 2019 at 01:53:23PM -0400, Michael S. Tsirkin wrote:
> > On Sun, Jul 21, 2019 at 06:17:25AM -0700, Paul E. McKenney wrote:
> > > On Sun, Jul 21, 2019 at 08:28:05AM -0400, Michael S. Tsirkin wrote:
> > > > Hi Paul, ot
On Sun, Jul 21, 2019 at 04:31:13PM -0700, Paul E. McKenney wrote:
> On Sun, Jul 21, 2019 at 02:08:37PM -0700, Matthew Wilcox wrote:
> > On Sun, Jul 21, 2019 at 06:17:25AM -0700, Paul E. McKenney wrote:
> > > Also, the overhead is important. For example, as far as I know,
> > > current RCU graceful
On Sun, Jul 21, 2019 at 02:08:37PM -0700, Matthew Wilcox wrote:
> On Sun, Jul 21, 2019 at 06:17:25AM -0700, Paul E. McKenney wrote:
> > Also, the overhead is important. For example, as far as I know,
> > current RCU gracefully handles close(open(...)) in a tight userspace
> > loop. But there migh
On Sun, Jul 21, 2019 at 06:17:25AM -0700, Paul E. McKenney wrote:
> Also, the overhead is important. For example, as far as I know,
> current RCU gracefully handles close(open(...)) in a tight userspace
> loop. But there might be trouble due to tight userspace loops around
> lighter-weight operat
On Sun, Jul 21, 2019 at 01:53:23PM -0400, Michael S. Tsirkin wrote:
> On Sun, Jul 21, 2019 at 06:17:25AM -0700, Paul E. McKenney wrote:
> > On Sun, Jul 21, 2019 at 08:28:05AM -0400, Michael S. Tsirkin wrote:
> > > Hi Paul, others,
> > >
> > > So it seems that vhost needs to call kfree_rcu from an
On Sun, Jul 21, 2019 at 06:17:25AM -0700, Paul E. McKenney wrote:
> On Sun, Jul 21, 2019 at 08:28:05AM -0400, Michael S. Tsirkin wrote:
> > Hi Paul, others,
> >
> > So it seems that vhost needs to call kfree_rcu from an ioctl. My worry
> > is what happens if userspace starts cycling through lots o
On Sun, Jul 21, 2019 at 08:28:05AM -0400, Michael S. Tsirkin wrote:
> Hi Paul, others,
>
> So it seems that vhost needs to call kfree_rcu from an ioctl. My worry
> is what happens if userspace starts cycling through lots of these
> ioctls. Given we actually use rcu as an optimization, we could ju
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