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[PATCH for-next v3 2/2] RDMA/rxe: Enable asynchronous prefetch for ODP MRs

Daisuke Matsuda posted 2 patches 9 months ago
There is a newer version of this series
[PATCH for-next v3 2/2] RDMA/rxe: Enable asynchronous prefetch for ODP MRs
Posted by Daisuke Matsuda 9 months ago 
Calling ibv_advise_mr(3) with flags other than IBV_ADVISE_MR_FLAG_FLUSH
invokes asynchronous request. It is best-effort, and thus can safely be
deferred to the system-wide workqueue.

Signed-off-by: Daisuke Matsuda <dskmtsd@gmail.com>
Reviewed-by: Zhu Yanjun <yanjun.zhu@linux.dev>
---
 drivers/infiniband/sw/rxe/rxe_odp.c | 84 ++++++++++++++++++++++++++++-
 1 file changed, 82 insertions(+), 2 deletions(-)

diff --git a/drivers/infiniband/sw/rxe/rxe_odp.c b/drivers/infiniband/sw/rxe/rxe_odp.c
index 4c98a02d572c..0f3b281a265f 100644
--- a/drivers/infiniband/sw/rxe/rxe_odp.c
+++ b/drivers/infiniband/sw/rxe/rxe_odp.c
@@ -425,6 +425,73 @@ enum resp_states rxe_odp_do_atomic_write(struct rxe_mr *mr, u64 iova, u64 value)
 	return RESPST_NONE;
 }
 
+struct prefetch_mr_work {
+	struct work_struct work;
+	u32 pf_flags;
+	u32 num_sge;
+	struct {
+		u64 io_virt;
+		struct rxe_mr *mr;
+		size_t length;
+	} frags[];
+};
+
+static void rxe_ib_prefetch_mr_work(struct work_struct *w)
+{
+	struct prefetch_mr_work *work =
+		container_of(w, struct prefetch_mr_work, work);
+	int ret;
+	u32 i;
+
+	/* We rely on IB/core that work is executed if we have num_sge != 0 only. */
+	WARN_ON(!work->num_sge);
+	for (i = 0; i < work->num_sge; ++i) {
+		struct ib_umem_odp *umem_odp;
+
+		ret = rxe_odp_do_pagefault_and_lock(work->frags[i].mr, work->frags[i].io_virt,
+						    work->frags[i].length, work->pf_flags);
+		if (ret < 0) {
+			rxe_dbg_mr(work->frags[i].mr, "failed to prefetch the mr\n");
+			continue;
+		}
+
+		umem_odp = to_ib_umem_odp(work->frags[i].mr->umem);
+		mutex_unlock(&umem_odp->umem_mutex);
+	}
+
+	kvfree(work);
+}
+
+static int rxe_init_prefetch_work(struct ib_pd *ibpd,
+				  enum ib_uverbs_advise_mr_advice advice,
+				  u32 pf_flags, struct prefetch_mr_work *work,
+				  struct ib_sge *sg_list, u32 num_sge)
+{
+	struct rxe_pd *pd = container_of(ibpd, struct rxe_pd, ibpd);
+	u32 i;
+
+	INIT_WORK(&work->work, rxe_ib_prefetch_mr_work);
+	work->pf_flags = pf_flags;
+
+	for (i = 0; i < num_sge; ++i) {
+		struct rxe_mr *mr;
+
+		mr = lookup_mr(pd, IB_ACCESS_LOCAL_WRITE,
+			       sg_list[i].lkey, RXE_LOOKUP_LOCAL);
+		if (IS_ERR(mr)) {
+			work->num_sge = i;
+			return PTR_ERR(mr);
+		}
+		work->frags[i].io_virt = sg_list[i].addr;
+		work->frags[i].length = sg_list[i].length;
+		work->frags[i].mr = mr;
+
+		rxe_put(mr);
+	}
+	work->num_sge = num_sge;
+	return 0;
+}
+
 static int rxe_ib_prefetch_sg_list(struct ib_pd *ibpd,
 				   enum ib_uverbs_advise_mr_advice advice,
 				   u32 pf_flags, struct ib_sge *sg_list,
@@ -475,6 +542,8 @@ static int rxe_ib_advise_mr_prefetch(struct ib_pd *ibpd,
 				     u32 flags, struct ib_sge *sg_list, u32 num_sge)
 {
 	u32 pf_flags = RXE_PAGEFAULT_DEFAULT;
+	struct prefetch_mr_work *work;
+	int rc;
 
 	if (advice == IB_UVERBS_ADVISE_MR_ADVICE_PREFETCH)
 		pf_flags |= RXE_PAGEFAULT_RDONLY;
@@ -487,8 +556,19 @@ static int rxe_ib_advise_mr_prefetch(struct ib_pd *ibpd,
 		return rxe_ib_prefetch_sg_list(ibpd, advice, pf_flags, sg_list,
 					       num_sge);
 
-	/* Asynchronous call is to be added in the next patch */
-	return -EOPNOTSUPP;
+	/* Asynchronous call is "best-effort" and allowed to fail */
+	work = kvzalloc(struct_size(work, frags, num_sge), GFP_KERNEL);
+	if (!work)
+		return -ENOMEM;
+
+	rc = rxe_init_prefetch_work(ibpd, advice, pf_flags, work, sg_list, num_sge);
+	if (rc) {
+		kvfree(work);
+		return rc;
+	}
+	queue_work(system_unbound_wq, &work->work);
+
+	return 0;
 }
 
 int rxe_ib_advise_mr(struct ib_pd *ibpd,
-- 
2.43.0
Re: [PATCH for-next v3 2/2] RDMA/rxe: Enable asynchronous prefetch for ODP MRs
Posted by Leon Romanovsky 8 months, 3 weeks ago 
On Tue, May 13, 2025 at 05:04:05AM +0000, Daisuke Matsuda wrote:
> Calling ibv_advise_mr(3) with flags other than IBV_ADVISE_MR_FLAG_FLUSH
> invokes asynchronous request. It is best-effort, and thus can safely be
> deferred to the system-wide workqueue.
> 
> Signed-off-by: Daisuke Matsuda <dskmtsd@gmail.com>
> Reviewed-by: Zhu Yanjun <yanjun.zhu@linux.dev>
> ---
>  drivers/infiniband/sw/rxe/rxe_odp.c | 84 ++++++++++++++++++++++++++++-
>  1 file changed, 82 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/infiniband/sw/rxe/rxe_odp.c b/drivers/infiniband/sw/rxe/rxe_odp.c
> index 4c98a02d572c..0f3b281a265f 100644
> --- a/drivers/infiniband/sw/rxe/rxe_odp.c
> +++ b/drivers/infiniband/sw/rxe/rxe_odp.c
> @@ -425,6 +425,73 @@ enum resp_states rxe_odp_do_atomic_write(struct rxe_mr *mr, u64 iova, u64 value)
>  	return RESPST_NONE;
>  }

<...>

> +static int rxe_init_prefetch_work(struct ib_pd *ibpd,
> +				  enum ib_uverbs_advise_mr_advice advice,
> +				  u32 pf_flags, struct prefetch_mr_work *work,
> +				  struct ib_sge *sg_list, u32 num_sge)

There is no need one-time called function. It can be embedded into rxe_ib_advise_mr_prefetch().

> +{

<...>

> @@ -475,6 +542,8 @@ static int rxe_ib_advise_mr_prefetch(struct ib_pd *ibpd,
>  				     u32 flags, struct ib_sge *sg_list, u32 num_sge)
>  {

<...>

> +	queue_work(system_unbound_wq, &work->work);

How do you ensure that this work isn't running after RXE is destroyed?

Thanks

> +
> +	return 0;
>  }
>  
>  int rxe_ib_advise_mr(struct ib_pd *ibpd,
> -- 
> 2.43.0
>
Re: [PATCH for-next v3 2/2] RDMA/rxe: Enable asynchronous prefetch for ODP MRs
Posted by Daisuke Matsuda 8 months, 3 weeks ago 
On 2025/05/18 14:54, Leon Romanovsky wrote:
> On Tue, May 13, 2025 at 05:04:05AM +0000, Daisuke Matsuda wrote:
>> Calling ibv_advise_mr(3) with flags other than IBV_ADVISE_MR_FLAG_FLUSH
>> invokes asynchronous request. It is best-effort, and thus can safely be
>> deferred to the system-wide workqueue.
>>
>> Signed-off-by: Daisuke Matsuda <dskmtsd@gmail.com>
>> Reviewed-by: Zhu Yanjun <yanjun.zhu@linux.dev>
>> ---
>>   drivers/infiniband/sw/rxe/rxe_odp.c | 84 ++++++++++++++++++++++++++++-
>>   1 file changed, 82 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/infiniband/sw/rxe/rxe_odp.c b/drivers/infiniband/sw/rxe/rxe_odp.c
>> index 4c98a02d572c..0f3b281a265f 100644
>> --- a/drivers/infiniband/sw/rxe/rxe_odp.c
>> +++ b/drivers/infiniband/sw/rxe/rxe_odp.c
>> @@ -425,6 +425,73 @@ enum resp_states rxe_odp_do_atomic_write(struct rxe_mr *mr, u64 iova, u64 value)
>>   	return RESPST_NONE;
>>   }
> 
> <...>
> 
>> +static int rxe_init_prefetch_work(struct ib_pd *ibpd,
>> +				  enum ib_uverbs_advise_mr_advice advice,
>> +				  u32 pf_flags, struct prefetch_mr_work *work,
>> +				  struct ib_sge *sg_list, u32 num_sge)
> 
> There is no need one-time called function. It can be embedded into rxe_ib_advise_mr_prefetch().

Certainly.

> 
>> +{
> 
> <...>
> 
>> @@ -475,6 +542,8 @@ static int rxe_ib_advise_mr_prefetch(struct ib_pd *ibpd,
>>   				     u32 flags, struct ib_sge *sg_list, u32 num_sge)
>>   {
> 
> <...>
> 
>> +	queue_work(system_unbound_wq, &work->work);
> 
> How do you ensure that this work isn't running after RXE is destroyed?

I think we can use per-pd reference counter in struct rxe_pd.
I will fix it in v4.

Thanks,
Daisuke

> 
> Thanks
> 
>> +
>> +	return 0;
>>   }
>>   
>>   int rxe_ib_advise_mr(struct ib_pd *ibpd,
>> -- 
>> 2.43.0
>>

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