Subject: Re: [PATCH v6 net-next 1/5] net: add generic per-cpu page_pool allocator

From: Lorenzo Bianconi <[email-masked]>
Date: Mon, 29 Jan 2024 14:04:37 +0100

> On 2024/1/28 22:20, Lorenzo Bianconi wrote:
> 
> >  #ifdef CONFIG_LOCKDEP
> >  /*
> >   * register_netdevice() inits txq->_xmit_lock and sets lockdep class
> > @@ -11686,6 +11690,27 @@ static void __init net_dev_struct_check(void)
> >   *
> >   */
> >  
> > +#define SD_PAGE_POOL_RING_SIZE	256
> 
> I might missed that if there is a reason we choose 256 here, do we
> need to use different value for differe page size, for 64K page size,
> it means we might need to reserve 16MB memory for each CPU.

honestly I have not spent time on it, most of the current page_pool users set
pool_size to 256. Anyway, do you mean something like:

diff --git a/net/core/dev.c b/net/core/dev.c
index f70fb6cad2b2..3934a3fc5c45 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -11806,12 +11806,11 @@ static void __init net_dev_struct_check(void)
  *
  */
 
-#define SD_PAGE_POOL_RING_SIZE	256
 static int net_page_pool_alloc(int cpuid)
 {
 #if IS_ENABLED(CONFIG_PAGE_POOL)
 	struct page_pool_params page_pool_params = {
-		.pool_size = SD_PAGE_POOL_RING_SIZE,
+		.pool_size = PAGE_SIZE < SZ_64K ? 256 : 16,
 		.nid = NUMA_NO_NODE,
 	};
 	struct page_pool *pp_ptr;

> 
> > +static int net_page_pool_alloc(int cpuid)
> > +{
> > +#if IS_ENABLED(CONFIG_PAGE_POOL)
> > +	struct page_pool_params page_pool_params = {
> > +		.pool_size = SD_PAGE_POOL_RING_SIZE,
> > +		.nid = NUMA_NO_NODE,
> > +	};
> > +	struct page_pool *pp_ptr;
> > +
> > +	pp_ptr = page_pool_create_percpu(&page_pool_params, cpuid);
> > +	if (IS_ERR(pp_ptr)) {
> > +		pp_ptr = NULL;
> 
> unnecessary NULL setting?

ack, I will get rid of it.

> 
> > +		return -ENOMEM;
> > +	}
> > +
> > +	per_cpu(page_pool, cpuid) = pp_ptr;
> > +#endif
> > +	return 0;
> > +}
> > +
> >  /*
> >   *       This is called single threaded during boot, so no need
> >   *       to take the rtnl semaphore.
> > @@ -11738,6 +11763,9 @@ static int __init net_dev_init(void)
> >  		init_gro_hash(&sd->backlog);
> >  		sd->backlog.poll = process_backlog;
> >  		sd->backlog.weight = weight_p;
> > +
> > +		if (net_page_pool_alloc(i))
> > +			goto out;
> >  	}
> >  
> >  	dev_boot_phase = 0;
> > @@ -11765,6 +11793,18 @@ static int __init net_dev_init(void)
> >  	WARN_ON(rc < 0);
> >  	rc = 0;
> >  out:
> > +	if (rc < 0) {
> > +		for_each_possible_cpu(i) {
> > +			struct page_pool *pp_ptr = this_cpu_read(page_pool);
> 
> this_cpu_read() -> per_cpu_ptr()?

ack, I will fix it.

Regards,
Lorenzo

> 
> > +
> > +			if (!pp_ptr)
> > +				continue;
> > +
> > +			page_pool_destroy(pp_ptr);
> > +			per_cpu(page_pool, i) = NULL;
> > +		}
> > +	}
> > +
> >  	return rc;
> >  }
> 
>