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Date: Wed, 16 Jun 2021 10:27:04 +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 v4 for-next 3/3] IB/core: Obtain subnet_prefix from cache
in IB devices
On Wed, Jun 16, 2021 at 12:22:13PM +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.
>
> In the situation of an event causing cache update, the subnet_prefix
> will get retrieved from newly updated GID cache in ib_cache_update(),
> so that we do not end up reading a stale value from cache via
> ib_query_port().
>
> Fixes: fad61ad ("IB/core: Add subnet prefix to port info")
> Suggested-by: Leon Romanovsky <leonro@...dia.com>
> Suggested-by: Aru Kolappan <aru.kolappan@...cle.com>
> 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().
> v3 -> v4:
> - Removed the enum ib_port_data_flags and 8 byte flags from
> struct ib_port_data, and the set_bit()/clear_bit() API
> used to update this flag as that was not necessary.
> Done to keep the code simple.
> - Added code to read subnet_prefix from updated GID cache in the
> event of cache update. Prior to this change, ib_cache_update
> was reading the value for subnet_prefix via ib_query_port(),
> due to this patch, we ended up reading a stale cached value of
> subnet_prefix.
>
> ---
> drivers/infiniband/core/cache.c | 18 +++++++++++++++---
> drivers/infiniband/core/device.c | 9 +++++++++
> include/rdma/ib_cache.h | 5 +++++
> include/rdma/ib_verbs.h | 1 +
> 4 files changed, 30 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/infiniband/core/cache.c b/drivers/infiniband/core/cache.c
> index 2325171..cd99c46 100644
> --- a/drivers/infiniband/core/cache.c
> +++ b/drivers/infiniband/core/cache.c
> @@ -917,9 +917,11 @@ 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) {
> + ib_dev->port_data[p].cache_is_initialized = 0;
I think that this line is not needed, we are removing device anyway and
and query_port is not allowed at this stage.
> 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)
> @@ -1466,6 +1468,7 @@ static int config_non_roce_gid_cache(struct ib_device *device,
> struct ib_port_attr *tprops = NULL;
> struct ib_pkey_cache *pkey_cache = NULL;
> struct ib_pkey_cache *old_pkey_cache = NULL;
> + union ib_gid gid;
> int i;
> int ret;
>
> @@ -1523,13 +1526,21 @@ static int config_non_roce_gid_cache(struct ib_device *device,
> device->port_data[port].cache.lmc = tprops->lmc;
> device->port_data[port].cache.port_state = tprops->state;
>
> - device->port_data[port].cache.subnet_prefix = tprops->subnet_prefix;
> + ret = rdma_query_gid(device, port, 0, &gid);
> + if (ret) {
> + write_unlock_irq(&device->cache.lock);
> + goto err;
> + }
> +
> + device->port_data[port].cache.subnet_prefix =
> + be64_to_cpu(gid.global.subnet_prefix);
> +
> write_unlock_irq(&device->cache_lock);
>
> if (enforce_security)
> ib_security_cache_change(device,
> port,
> - tprops->subnet_prefix);
> + be64_to_cpu(gid.global.subnet_prefix));
>
> kfree(old_pkey_cache);
> kfree(tprops);
> @@ -1629,6 +1640,7 @@ int ib_cache_setup_one(struct ib_device *device)
> err = ib_cache_update(device, p, true, true, true);
> if (err)
> return err;
> + device->port_data[p].cache_is_initialized = 1;
> }
>
> return 0;
> diff --git a/drivers/infiniband/core/device.c b/drivers/infiniband/core/device.c
> index 7a617e4..57b9039 100644
> --- a/drivers/infiniband/core/device.c
> +++ b/drivers/infiniband/core/device.c
> @@ -2057,6 +2057,15 @@ 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;
IMHO, we don't need this new function and can access ib_port_data
directly. In device.c, we have plenty of places that does it.
Not critical.
> +
> + 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 226ae37..46b43a7 100644
> --- a/include/rdma/ib_cache.h
> +++ b/include/rdma/ib_cache.h
> @@ -114,4 +114,9 @@ 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,
> + u32 port_num)
> +{
> + return device->port_data[port_num].cache_is_initialized;
> +}
> #endif /* _IB_CACHE_H */
> diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
> index c96d601..405f7da 100644
> --- a/include/rdma/ib_verbs.h
> +++ b/include/rdma/ib_verbs.h
> @@ -2177,6 +2177,7 @@ struct ib_port_data {
>
> spinlock_t netdev_lock;
>
> + u8 cache_is_initialized:1;
> struct list_head pkey_list;
>
> struct ib_port_cache cache;
> --
> 1.8.3.1
>
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