Subject: [PATCH] xprtrdma: Make sure Send CQ is allocated on an existing CPU

Make sure host has at least 2 CPU before allocating to CPU#1

Fixes: a4699f5647f3 (xprtrdma: Put Send CQ in IB_POLL_WORKQUEUE mode)
Signed-off-by: Nicolas Morey-Chaisemartin <[email protected]>
---
net/sunrpc/xprtrdma/verbs.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
index b725911c0f3f..36aa7b2648e4 100644
--- a/net/sunrpc/xprtrdma/verbs.c
+++ b/net/sunrpc/xprtrdma/verbs.c
@@ -546,7 +546,7 @@ rpcrdma_ep_create(struct rpcrdma_ep *ep, struct rpcrdma_ia *ia,

sendcq = ib_alloc_cq(ia->ri_device, NULL,
ep->rep_attr.cap.max_send_wr + 1,
- 1, IB_POLL_WORKQUEUE);
+ num_online_cpus() > 1 ? 1 : 0, IB_POLL_WORKQUEUE);
if (IS_ERR(sendcq)) {
rc = PTR_ERR(sendcq);
dprintk("RPC: %s: failed to create send CQ: %i\n",
--
2.18.0



2019-01-23 16:51:37

by Chuck Lever III

[permalink] [raw]
Subject: Re: [PATCH] xprtrdma: Make sure Send CQ is allocated on an existing CPU

Hi Nicolas-

> On Jan 23, 2019, at 8:12 AM, Nicolas Morey-Chaisemartin <[email protected]> wrote:
>
> Make sure host has at least 2 CPU before allocating to CPU#1

The fourth parameter of ib_alloc_cq() is not a CPU number,
it's a completion vector number. What failure did you see
that prompted this patch?


> Fixes: a4699f5647f3 (xprtrdma: Put Send CQ in IB_POLL_WORKQUEUE mode)
> Signed-off-by: Nicolas Morey-Chaisemartin <[email protected]>
> ---
> net/sunrpc/xprtrdma/verbs.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
> index b725911c0f3f..36aa7b2648e4 100644
> --- a/net/sunrpc/xprtrdma/verbs.c
> +++ b/net/sunrpc/xprtrdma/verbs.c
> @@ -546,7 +546,7 @@ rpcrdma_ep_create(struct rpcrdma_ep *ep, struct rpcrdma_ia *ia,
>
> sendcq = ib_alloc_cq(ia->ri_device, NULL,
> ep->rep_attr.cap.max_send_wr + 1,
> - 1, IB_POLL_WORKQUEUE);
> + num_online_cpus() > 1 ? 1 : 0, IB_POLL_WORKQUEUE);
> if (IS_ERR(sendcq)) {
> rc = PTR_ERR(sendcq);
> dprintk("RPC: %s: failed to create send CQ: %i\n",
> --
> 2.18.0
>

--
Chuck Lever




Subject: Re: [PATCH] xprtrdma: Make sure Send CQ is allocated on an existing CPU



On 1/23/19 5:51 PM, Chuck Lever wrote:
> Hi Nicolas-
>
>> On Jan 23, 2019, at 8:12 AM, Nicolas Morey-Chaisemartin <[email protected]> wrote:
>>
>> Make sure host has at least 2 CPU before allocating to CPU#1
> The fourth parameter of ib_alloc_cq() is not a CPU number,
> it's a completion vector number. What failure did you see
> that prompted this patch?
When trying to mount, I get this:
+ mount -o rdma,port=20049 192.168.20.15:/tmp/RAM /tmp/RAM
mount.nfs: mounting 192.168.20.15:/tmp/RAM failed, reason given by server: No such file or directory

Digging a bit into the code, it appears that the cq allocation here returns a ENOENT which come from mlx5_vector2eqn.
On my system (VM with a mlx5 card with SRIOV), the comp_eqs_list only contains one entry with index == 0

Nicolas

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Subject: Re: [PATCH] xprtrdma: Make sure Send CQ is allocated on an existing CPU



On 1/23/19 6:06 PM, Nicolas Morey-Chaisemartin wrote:
>
> On 1/23/19 5:51 PM, Chuck Lever wrote:
>> Hi Nicolas-
>>
>>> On Jan 23, 2019, at 8:12 AM, Nicolas Morey-Chaisemartin <[email protected]> wrote:
>>>
>>> Make sure host has at least 2 CPU before allocating to CPU#1
>> The fourth parameter of ib_alloc_cq() is not a CPU number,
>> it's a completion vector number. What failure did you see
>> that prompted this patch?
> When trying to mount, I get this:
> + mount -o rdma,port=20049 192.168.20.15:/tmp/RAM /tmp/RAM
> mount.nfs: mounting 192.168.20.15:/tmp/RAM failed, reason given by server: No such file or directory
>
> Digging a bit into the code, it appears that the cq allocation here returns a ENOENT which come from mlx5_vector2eqn.
> On my system (VM with a mlx5 card with SRIOV), the comp_eqs_list only contains one entry with index == 0
>
> Nicolas
>

Also, adding a 2nd core to my VM fixes the issue (thus my understanding that it was a CPU number)

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2019-01-23 17:30:37

by Chuck Lever III

[permalink] [raw]
Subject: Re: [PATCH] xprtrdma: Make sure Send CQ is allocated on an existing CPU



> On Jan 23, 2019, at 12:07 PM, Nicolas Morey-Chaisemartin <[email protected]> wrote:
>
>
>
> On 1/23/19 6:06 PM, Nicolas Morey-Chaisemartin wrote:
>>
>> On 1/23/19 5:51 PM, Chuck Lever wrote:
>>> Hi Nicolas-
>>>
>>>> On Jan 23, 2019, at 8:12 AM, Nicolas Morey-Chaisemartin <[email protected]> wrote:
>>>>
>>>> Make sure host has at least 2 CPU before allocating to CPU#1
>>> The fourth parameter of ib_alloc_cq() is not a CPU number,
>>> it's a completion vector number. What failure did you see
>>> that prompted this patch?
>> When trying to mount, I get this:
>> + mount -o rdma,port=20049 192.168.20.15:/tmp/RAM /tmp/RAM
>> mount.nfs: mounting 192.168.20.15:/tmp/RAM failed, reason given by server: No such file or directory
>>
>> Digging a bit into the code, it appears that the cq allocation here returns a ENOENT which come from mlx5_vector2eqn.
>> On my system (VM with a mlx5 card with SRIOV), the comp_eqs_list only contains one entry with index == 0
>>
>> Nicolas
>>
>
> Also, adding a 2nd core to my VM fixes the issue (thus my understanding that it was a CPU number)

Fair enough. The 2nd CPU adds a 2nd compvec. Instead of
num_cpus_online() you want ib_device::num_comp_vectors.

I suspect there's a spiffier way to go about this these
days thanks to ib_get_vector_affinity, but you've found
a longstanding bug. So let's get something that can be
comfortably backported to stable.


--
Chuck Lever