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Date:   Thu, 1 Dec 2022 11:41:13 -0700
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Subject: Re: [PATCH 6/6] eventpoll: add support for min-wait
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To:     Soheil Hassas Yeganeh <soheil@google.com>
Cc:     linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
        Willem de Bruijn <willemb@google.com>,
        Shakeel Butt <shakeelb@google.com>
References: <20221030220203.31210-1-axboe@kernel.dk>
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From:   Jens Axboe <axboe@kernel.dk>
In-Reply-To: <CACSApvZU0o3MSp33G0Ld+1dr-k82UCcJqF=40AVL-F6UXHpGgg@mail.gmail.com>
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On 12/1/22 11:39 AM, Soheil Hassas Yeganeh wrote:
> On Thu, Dec 1, 2022 at 1:00 PM Jens Axboe <axboe@kernel.dk> wrote:
>>
>>>>> @@ -1845,6 +1891,18 @@ static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
>>>>>             ewq.timed_out = true;
>>>>>     }
>>>>>
>>>>> +   /*
>>>>> +    * If min_wait is set for this epoll instance, note the min_wait
>>>>> +    * time. Ensure the lowest bit is set in ewq.min_wait_ts, that's
>>>>> +    * the state bit for whether or not min_wait is enabled.
>>>>> +    */
>>>>> +   if (ep->min_wait_ts) {
>>>>
>>>> Can we limit this block to "ewq.timed_out && ep->min_wait_ts"?
>>>> AFAICT, the code we run here is completely wasted if timeout is 0.
>>>
>>> Yep certainly, I can gate it on both of those conditions.
>> Looking at this for a respin, I think it should be gated on
>> !ewq.timed_out? timed_out == true is the path that it's wasted on
>> anyway.
> 
> Ah, yes, that's a good point. The check should be !ewq.timed_out.

The just posted v4 has the check (and the right one :-))

-- 
Jens Axboe