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Message-ID: <d80308c7-ac9d-b7e5-a465-a51bf42f5146@oracle.com>
Date: Wed, 16 Jun 2021 13:35:09 +0530
From: Anand Khoje <anand.a.khoje@...cle.com>
To: Leon Romanovsky <leon@...nel.org>
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 6/16/2021 1:12 PM, Anand Khoje wrote:
> On 6/16/2021 12:57 PM, Leon Romanovsky wrote:
>> 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.
>>
> We have kept this for code completeness purposes. Just as we did with
> set_bit() and clear_bit() APIs.
>
>>> 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.
>>
> Added this function to have a way to check validity of cache, such that
> it could be used in future for the same check in areas to which
> ib_port_data is opaque.
>
Also, there was a review comment from Mark Zhang for patch version 2,
where he had suggested to shift clear_bit(IB_PORT_CACHE_INITIALIZED,
&device->port_data[p].flags);
to gid_table_cleanup_one().
Thanks,
Anand
>>> +
>>> + 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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