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Date: Wed, 9 Jun 2021 13:40:17 +0300
From: Leon Romanovsky <leon@...nel.org>
To: Anand Khoje <anand.a.khoje@...cle.com>
Cc: "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"dledford@...hat.com" <dledford@...hat.com>,
"jgg@...pe.ca" <jgg@...pe.ca>,
Haakon Bugge <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 09:26:03AM +0000, Anand Khoje wrote:
> Hi Leon,
Please don't do top-posting.
>
> The set_bit()/clear_bit() and enum ib_port_data_flags has been added as a device that can be used for future enhancements.
> Also, usage of set_bit()/clear_bit() ensures the operations on this bit is atomic.
The bitfield variables are better suit this use case.
Let's don't overcomplicate code without the reason.
Thanks
>
> Thanks,
> Anand
>
> -----Original Message-----
> From: Leon Romanovsky <leon@...nel.org>
> Sent: Wednesday, June 9, 2021 2:06 PM
> 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 <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
> >
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