Re: [RFC workqueue/driver-core PATCH 2/5] async: Add support for queueing on specific NUMA node

[Alexander Duyck]

On 9/26/2018 5:31 PM, Dan Williams wrote:
> On Wed, Sep 26, 2018 at 2:51 PM Alexander Duyck
> <alexander.h.duyck@xxxxxxxxxxxxxxx> wrote:
> > This patch introduces four new variants of the async_schedule_ functions
> > that allow scheduling on a specific NUMA node.
> >
> > The first two functions are async_schedule_near and
> > async_schedule_near_domain which end up mapping to async_schedule and
> > async_schedule_domain but provide NUMA node specific functionality. They
> > replace the original functions which were moved to inline function
> > definitions that call the new functions while passing NUMA_NO_NODE.
> >
> > The second two functions are async_schedule_dev and
> > async_schedule_dev_domain which provide NUMA specific functionality when
> > passing a device as the data member and that device has a NUMA node other
> > than NUMA_NO_NODE.
> >
> > The main motivation behind this is to address the need to be able to
> > schedule device specific init work on specific NUMA nodes in order to
> > improve performance of memory initialization.
> >
> > Signed-off-by: Alexander Duyck <alexander.h.duyck@xxxxxxxxxxxxxxx>
> [..]
> >   /**
> > - * async_schedule - schedule a function for asynchronous execution
> > + * async_schedule_near - schedule a function for asynchronous execution
> >    * @func: function to execute asynchronously
> >    * @data: data pointer to pass to the function
> > + * @node: NUMA node that we want to schedule this on or close to
> >    *
> >    * Returns an async_cookie_t that may be used for checkpointing later.
> >    * Note: This function may be called from atomic or non-atomic contexts.
> >    */
> > -async_cookie_t async_schedule(async_func_t func, void *data)
> > +async_cookie_t async_schedule_near(async_func_t func, void *data, int node)
> >   {
> > -       return __async_schedule(func, data, &async_dfl_domain);
> > +       return async_schedule_near_domain(func, data, node, &async_dfl_domain);
> >   }
> > -EXPORT_SYMBOL_GPL(async_schedule);
> > +EXPORT_SYMBOL_GPL(async_schedule_near);
>
> Looks good to me. The _near() suffix makes it clear that we're doing a
> best effort hint to the work placement compared to the strict
> expectations of _on routines.
>
> >   /**
> > - * async_schedule_domain - schedule a function for asynchronous execution within a certain domain
> > + * async_schedule_dev_domain - schedule a function for asynchronous execution within a certain domain
> >    * @func: function to execute asynchronously
> > - * @data: data pointer to pass to the function
> > + * @dev: device that we are scheduling this work for
> >    * @domain: the domain
> >    *
> > - * Returns an async_cookie_t that may be used for checkpointing later.
> > - * @domain may be used in the async_synchronize_*_domain() functions to
> > - * wait within a certain synchronization domain rather than globally.  A
> > - * synchronization domain is specified via @domain.  Note: This function
> > - * may be called from atomic or non-atomic contexts.
> > + * Device specific version of async_schedule_near_domain that provides some
> > + * NUMA awareness based on the device node.
> > + */
> > +async_cookie_t async_schedule_dev_domain(async_func_t func, struct device *dev,
> > +                                        struct async_domain *domain)
> > +{
> > +       return async_schedule_near_domain(func, dev, dev_to_node(dev), domain);
> > +}
> > +EXPORT_SYMBOL_GPL(async_schedule_dev_domain);
>
> This seems unnecessary and restrictive. Callers may want to pass
> something other than dev as the parameter to the async function, and
> dev_to_node() is not on onerous burden to place on callers.


That is what async_schedule_near_domain is for, they can call that. The 
"dev" versions of the calls as just supposed to be helpers since one of 
the most common parameters to the async_schedule calls is a device, so I 
thought I would just put together a function that takes care of all this 
for us so I could drop an argument and avoid having to use dev_to_node 
everywhere.