linux-kernel - Re: [PATCH v3 3/3] IB/core: Obtain subnet

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Date:   Wed, 9 Jun 2021 11:36:19 +0300
From:   Leon Romanovsky <leon@...nel.org>
To:     Anand Khoje <anand.a.khoje@...cle.com>
Cc:     linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
        dledford@...hat.com, jgg@...pe.ca, haakon.bugge@...cle.com
Subject: Re: [PATCH v3 3/3] IB/core: Obtain subnet_prefix from cache in IB
 devices.

On Wed, Jun 09, 2021 at 11:25:34AM +0530, Anand Khoje wrote:
> ib_query_port() calls device->ops.query_port() to get the port
> attributes. The method of querying is device driver specific.
> The same function calls device->ops.query_gid() to get the GID and
> extract the subnet_prefix (gid_prefix).
> 
> The GID and subnet_prefix are stored in a cache. But they do not get
> read from the cache if the device is an Infiniband device. The
> following change takes advantage of the cached subnet_prefix.
> Testing with RDBMS has shown a significant improvement in performance
> with this change.
> 
> The function ib_cache_is_initialised() is introduced because
> ib_query_port() gets called early in the stage when the cache is not
> built while reading port immutable property.
> 
> In that case, the default GID still gets read from HCA for IB link-
> layer devices.
> 
> Fixes: fad61ad ("IB/core: Add subnet prefix to port info")
> Signed-off-by: Anand Khoje <anand.a.khoje@...cle.com>
> Signed-off-by: Haakon Bugge <haakon.bugge@...cle.com>
> 
> ---
> 
> v1 -> v2:
>     -	Split the v1 patch in 3 patches as per Leon's suggestion.
> 
> v2 -> v3:
>     -	Added changes as per Mark Zhang's suggestion of clearing
>     	flags in git_table_cleanup_one().
> 
> ---
>  drivers/infiniband/core/cache.c  | 7 ++++++-
>  drivers/infiniband/core/device.c | 9 +++++++++
>  include/rdma/ib_cache.h          | 6 ++++++
>  include/rdma/ib_verbs.h          | 6 ++++++
>  4 files changed, 27 insertions(+), 1 deletion(-)

Why did you use clear_bit/test_bit API? I would expect it for the
bitmap, but for such simple thing, the simple "u8 is_cached_init : 1;"
will do the same trick.

Thanks

> 
> diff --git a/drivers/infiniband/core/cache.c b/drivers/infiniband/core/cache.c
> index e957f0c915a3..94a8653a72c5 100644
> --- a/drivers/infiniband/core/cache.c
> +++ b/drivers/infiniband/core/cache.c
> @@ -917,9 +917,12 @@ static void gid_table_cleanup_one(struct ib_device *ib_dev)
>  {
>  	u32 p;
>  
> -	rdma_for_each_port (ib_dev, p)
> +	rdma_for_each_port (ib_dev, p) {
> +		clear_bit(IB_PORT_CACHE_INITIALIZED,
> +			&ib_dev->port_data[p].flags);
>  		cleanup_gid_table_port(ib_dev, p,
>  				       ib_dev->port_data[p].cache.gid);
> +	}
>  }
>  
>  static int gid_table_setup_one(struct ib_device *ib_dev)
> @@ -1623,6 +1626,8 @@ int ib_cache_setup_one(struct ib_device *device)
>  		err = ib_cache_update(device, p, true);
>  		if (err)
>  			return err;
> +		set_bit(IB_PORT_CACHE_INITIALIZED,
> +			&device->port_data[p].flags);
>  	}
>  
>  	return 0;
> diff --git a/drivers/infiniband/core/device.c b/drivers/infiniband/core/device.c
> index 595128b26c34..e8e7b0a61411 100644
> --- a/drivers/infiniband/core/device.c
> +++ b/drivers/infiniband/core/device.c
> @@ -2059,6 +2059,15 @@ static int __ib_query_port(struct ib_device *device,
>  	    IB_LINK_LAYER_INFINIBAND)
>  		return 0;
>  
> +	if (!ib_cache_is_initialised(device, port_num))
> +		goto query_gid_from_device;
> +
> +	ib_get_cached_subnet_prefix(device, port_num,
> +				    &port_attr->subnet_prefix);
> +
> +	return 0;
> +
> +query_gid_from_device:
>  	err = device->ops.query_gid(device, port_num, 0, &gid);
>  	if (err)
>  		return err;
> diff --git a/include/rdma/ib_cache.h b/include/rdma/ib_cache.h
> index 226ae3702d8a..1526fc6637eb 100644
> --- a/include/rdma/ib_cache.h
> +++ b/include/rdma/ib_cache.h
> @@ -114,4 +114,10 @@ ssize_t rdma_query_gid_table(struct ib_device *device,
>  			     struct ib_uverbs_gid_entry *entries,
>  			     size_t max_entries);
>  
> +static inline bool ib_cache_is_initialised(struct ib_device *device,
> +					  u8 port_num)
> +{
> +	return test_bit(IB_PORT_CACHE_INITIALIZED,
> +			&device->port_data[port_num].flags);
> +}
>  #endif /* _IB_CACHE_H */
> diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
> index 41cbec516424..ad2a55e3a2ee 100644
> --- a/include/rdma/ib_verbs.h
> +++ b/include/rdma/ib_verbs.h
> @@ -2169,6 +2169,10 @@ struct ib_port_immutable {
>  	u32                           max_mad_size;
>  };
>  
> +enum ib_port_data_flags {
> +	IB_PORT_CACHE_INITIALIZED = 1 << 0,
> +};
> +
>  struct ib_port_data {
>  	struct ib_device *ib_dev;
>  
> @@ -2178,6 +2182,8 @@ struct ib_port_data {
>  
>  	spinlock_t netdev_lock;
>  
> +	unsigned long flags;
> +
>  	struct list_head pkey_list;
>  
>  	struct ib_port_cache cache;
> -- 
> 2.27.0
>