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 14:35:14 -0700
From:   Manjunath Patil <manjunath.b.patil@...cle.com>
To:     santosh.shilimkar@...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 9/16/2020 2:25 PM, santosh.shilimkar@...cle.com wrote:
> On 9/16/20 2:15 PM, Manjunath Patil wrote:
>> Hi Santosh,
>>
>> inline.
>> On 9/16/2020 12:27 PM, santosh.shilimkar@...cle.com wrote:
>>> 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.
>> I will add new line. checkpatch.pl didn't find it though.
>>>> +            /* 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()" ?
>> I think you meant, get rid of if clause and use 
>> "pr_warn_ratelimited()" instead.
>> That can still produce more than needed logs during low memory 
>> situation.
>>
> Try it out. It will do the same job as what you are trying to do.
Sure. I will use it and see. I will submit next version after my testing.

-Thanks,
Manjunath