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

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Date:   Thu, 27 Sep 2018 08:16:33 -0700
From:   Alexander Duyck <alexander.h.duyck@...ux.intel.com>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     linux-nvdimm <linux-nvdimm@...ts.01.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        Linux-pm mailing list <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Tejun Heo <tj@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Brown, Len" <len.brown@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Vishal L Verma <vishal.l.verma@...el.com>,
        jiangshanlai@...il.com, Pavel Machek <pavel@....cz>,
        zwisler@...nel.org
Subject: Re: [RFC workqueue/driver-core PATCH 2/5] async: Add support for
 queueing on specific NUMA node



On 9/26/2018 5:31 PM, Dan Williams wrote:
> On Wed, Sep 26, 2018 at 2:51 PM Alexander Duyck
> <alexander.h.duyck@...ux.intel.com> 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@...ux.intel.com>
> [..]
>>   /**
>> - * 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.