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IB/cma: Use cached gids 

The cma_acquire_dev function was changed by commit 3c86aa70bf
("RDMA/cm: Add RDMA CM support for IBoE devices") to use find_gid_port()
because multiport devices might have either IB or IBoE formatted gids.
The old function assumed that all ports on the same device used the
same GID format.

However, when it was changed to use find_gid_port(), we inadvertently
lost usage of the GID cache.  This turned out to be a very costly
change.  In our testing, each iteration through each index of the GID
table takes roughly 35us.  When you have multiple devices in a system,
and the GID you are looking for is on one of the later devices, the
code loops through all of the GID indexes on all of the early devices
before it finally succeeds on the target device.  This pathological
search behavior combined with 35us per GID table index retrieval
results in results such as the following from the cmtime application
that's part of the latest librdmacm git repo:

ib1:
step              total ms     max ms     min us  us / conn
create id    :       29.42       0.04       1.00       2.94
bind addr    :   186705.66      19.00   18556.00   18670.57
resolve addr :       41.93       9.68     619.00       4.19
resolve route:      486.93       0.48     101.00      48.69
create qp    :     4021.95       6.18     330.00     402.20
connect      :    68350.39   68588.17   24632.00    6835.04
disconnect   :     1460.43     252.65-1862269.00     146.04
destroy      :       41.16       0.04       2.00       4.12

ib0:
step              total ms     max ms     min us  us / conn
create id    :       28.61       0.68       1.00       2.86
bind addr    :     2178.86       2.95     201.00     217.89
resolve addr :       51.26      16.85     845.00       5.13
resolve route:      620.08       0.43      92.00      62.01
create qp    :     3344.40       6.36     273.00     334.44
connect      :     6435.99    6368.53    7844.00     643.60
disconnect   :     5095.38     321.90     757.00     509.54
destroy      :       37.13       0.02       2.00       3.71

Clearly, both the bind address and connect operations suffer
a huge penalty for being anything other than the default
GID on the first port in the system.

After applying this patch, the numbers now look like this:

ib1:
step              total ms     max ms     min us  us / conn
create id    :       30.15       0.03       1.00       3.01
bind addr    :       80.27       0.04       7.00       8.03
resolve addr :       43.02      13.53     589.00       4.30
resolve route:      482.90       0.45     100.00      48.29
create qp    :     3986.55       5.80     330.00     398.66
connect      :     7141.53    7051.29    5005.00     714.15
disconnect   :     5038.85     193.63     918.00     503.88
destroy      :       37.02       0.04       2.00       3.70

ib0:
step              total ms     max ms     min us  us / conn
create id    :       34.27       0.05       1.00       3.43
bind addr    :       26.45       0.04       1.00       2.64
resolve addr :       38.25      10.54     760.00       3.82
resolve route:      604.79       0.43      97.00      60.48
create qp    :     3314.95       6.34     273.00     331.49
connect      :    12399.26   12351.10    8609.00    1239.93
disconnect   :     5096.76     270.72    1015.00     509.68
destroy      :       37.10       0.03       2.00       3.71

It's worth noting that we still suffer a bit of a penalty on
connect to the wrong device, but the penalty is much less than
it used to be.  Follow on patches deal with this penalty.

Many thanks to Neil Horman for helping to track the source of
slow function that allowed us to track down the fact that
the original patch I mentioned above backed out cache usage
and identify just how much that impacted the system.

Signed-off-by: Doug Ledford <dledford@redhat.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>
This commit is contained in:
Doug Ledford 2013-09-24 17:16:27 -04:00 committed by Roland Dreier
parent 959f58544b
commit 29f27e8477
1 changed files with 6 additions and 29 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

35
drivers/infiniband/core/cma.c
View File

@ -328,28 +328,6 @@ static int cma_set_qkey(struct rdma_id_private *id_priv, u32 qkey)
return ret;
}
static int find_gid_port(struct ib_device *device, union ib_gid *gid, u8 port_num)
{
int i;
int err;
struct ib_port_attr props;
union ib_gid tmp;
err = ib_query_port(device, port_num, &props);
if (err)
return err;
for (i = 0; i < props.gid_tbl_len; ++i) {
err = ib_query_gid(device, port_num, i, &tmp);
if (err)
return err;
if (!memcmp(&tmp, gid, sizeof tmp))
return 0;
}
return -EADDRNOTAVAIL;
}
static void cma_translate_ib(struct sockaddr_ib *sib, struct rdma_dev_addr *dev_addr)
{
dev_addr->dev_type = ARPHRD_INFINIBAND;
@ -377,7 +355,7 @@ static int cma_acquire_dev(struct rdma_id_private *id_priv)
struct cma_device *cma_dev;
union ib_gid gid, iboe_gid;
int ret = -ENODEV;
u8 port;
u8 port, found_port;
enum rdma_link_layer dev_ll = dev_addr->dev_type == ARPHRD_INFINIBAND ?
IB_LINK_LAYER_INFINIBAND : IB_LINK_LAYER_ETHERNET;
@ -390,21 +368,20 @@ static int cma_acquire_dev(struct rdma_id_private *id_priv)
memcpy(&gid, dev_addr->src_dev_addr +
rdma_addr_gid_offset(dev_addr), sizeof gid);
list_for_each_entry(cma_dev, &dev_list, list) {
for (port = 1; port <= cma_dev->device->phys_port_cnt; ++port) {
for (port = 1; port <= cma_dev->device->phys_port_cnt; ++port)
if (rdma_port_get_link_layer(cma_dev->device, port) == dev_ll) {
if (rdma_node_get_transport(cma_dev->device->node_type) == RDMA_TRANSPORT_IB &&
rdma_port_get_link_layer(cma_dev->device, port) == IB_LINK_LAYER_ETHERNET)
ret = find_gid_port(cma_dev->device, &iboe_gid, port);
ret = ib_find_cached_gid(cma_dev->device, &iboe_gid, &found_port, NULL);
else
ret = find_gid_port(cma_dev->device, &gid, port);
ret = ib_find_cached_gid(cma_dev->device, &gid, &found_port, NULL);
if (!ret) {
id_priv->id.port_num = port;
if (!ret && (port == found_port)) {
id_priv->id.port_num = found_port;
goto out;
}
}
}
}
out:
if (!ret)