netdev - Re: [PATCH 1/1] net/rds: suppress page allocation failure error in recv buffer refill

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Date:   Wed, 16 Sep 2020 12:27:40 -0700
From:   santosh.shilimkar@...cle.com
To:     Manjunath Patil <manjunath.b.patil@...cle.com>
Cc:     netdev@...r.kernel.org, linux-rdma@...r.kernel.org,
        aruna.ramakrishna@...cle.com, rama.nichanamatlu@...cle.com
Subject: Re: [PATCH 1/1] net/rds: suppress page allocation failure error in
 recv buffer refill

On 9/16/20 12:08 PM, Manjunath Patil wrote:
> RDS/IB tries to refill the recv buffer in softirq context using
> GFP_NOWAIT flag. However alloc failure is handled by queueing a work to
> refill the recv buffer with GFP_KERNEL flag. This means failure to
> allocate with GFP_NOWAIT isn't fatal. Do not print the PAF warnings if
> softirq context fails to refill the recv buffer, instead print a one
> line warning once a day.
> 
> Signed-off-by: Manjunath Patil <manjunath.b.patil@...cle.com>
> Reviewed-by: Aruna Ramakrishna <aruna.ramakrishna@...cle.com>
> ---
>   net/rds/ib_recv.c | 16 +++++++++++++---
>   1 file changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/net/rds/ib_recv.c b/net/rds/ib_recv.c
> index 694d411dc72f..38d2894f6bb2 100644
> --- a/net/rds/ib_recv.c
> +++ b/net/rds/ib_recv.c
> @@ -310,8 +310,8 @@ static int rds_ib_recv_refill_one(struct rds_connection *conn,
>   	struct rds_ib_connection *ic = conn->c_transport_data;
>   	struct ib_sge *sge;
>   	int ret = -ENOMEM;
> -	gfp_t slab_mask = GFP_NOWAIT;
> -	gfp_t page_mask = GFP_NOWAIT;
> +	gfp_t slab_mask = gfp;
> +	gfp_t page_mask = gfp;
>   
>   	if (gfp & __GFP_DIRECT_RECLAIM) {
>   		slab_mask = GFP_KERNEL;
> @@ -406,6 +406,16 @@ void rds_ib_recv_refill(struct rds_connection *conn, int prefill, gfp_t gfp)
>   		recv = &ic->i_recvs[pos];
>   		ret = rds_ib_recv_refill_one(conn, recv, gfp);
>   		if (ret) {
> +			static unsigned long warn_time;
Comment should start on next line.
> +			/* warn max once per day. This should be enough to
> +			 * warn users about low mem situation.
> +			 */
> +			if (printk_timed_ratelimit(&warn_time,
> +						   24 * 60 * 60 * 1000))
> +				pr_warn("RDS/IB: failed to refill recv buffer for <%pI6c,%pI6c,%d>, waking worker\n",
> +					&conn->c_laddr, &conn->c_faddr,
> +					conn->c_tos);
Didn't notice this before.
Why not just use "pr_warn_ratelimited()" ?
> +
>   			must_wake = true;
>   			break;
>   		}
> @@ -1020,7 +1030,7 @@ void rds_ib_recv_cqe_handler(struct rds_ib_connection *ic,
>   		rds_ib_stats_inc(s_ib_rx_ring_empty);
>   
>   	if (rds_ib_ring_low(&ic->i_recv_ring)) {
> -		rds_ib_recv_refill(conn, 0, GFP_NOWAIT);
> +		rds_ib_recv_refill(conn, 0, GFP_NOWAIT | __GFP_NOWARN);
>   		rds_ib_stats_inc(s_ib_rx_refill_from_cq);
>   	}
>   }
>