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From: Pavel Begunkov <asml.silence@gmail.com>
To: Dennis Zhou <dennis@kernel.org>, Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>,
	io-uring@vger.kernel.org, linux-kernel@vger.kernel.org,
	Christoph Lameter <cl@linux.com>
Subject: Re: [PATCH 1/2] pcpu_ref: add percpu_ref_tryget_many()
Date: Sat, 21 Dec 2019 18:36:32 +0300
Message-ID: <e90c5695-0357-a5e0-3c3a-64594c6e55a2@gmail.com> (raw)
In-Reply-To: <20191218174955.GA14991@dennisz-mbp.dhcp.thefacebook.com>

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On 18/12/2019 20:49, Dennis Zhou wrote:
> On Wed, Dec 18, 2019 at 08:26:42AM -0800, Tejun Heo wrote:
>> (cc'ing Dennis and Christoph and quoting whole body)
>>
>> Pavel, can you please cc percpu maintainers on related changes?

My bad, lost cc's in the way.

>>
>> The patch looks fine to me.  Please feel free to add my acked-by.
>>
>> On Tue, Dec 17, 2019 at 04:42:59PM -0700, Jens Axboe wrote:
>>> CC Tejun on this one. Looks fine to me, and matches the put path.

Thanks both for taking a look!

>>>
>>>
>>> On 12/17/19 3:28 PM, Pavel Begunkov wrote:
>>>> Add percpu_ref_tryget_many(), which works the same way as
>>>> percpu_ref_tryget(), but grabs specified number of refs.
>>>>
>>>> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
>>>> ---
>>>>  include/linux/percpu-refcount.h | 24 ++++++++++++++++++++----
>>>>  1 file changed, 20 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/include/linux/percpu-refcount.h b/include/linux/percpu-refcount.h
>>>> index 390031e816dc..19079b62ce31 100644
>>>> --- a/include/linux/percpu-refcount.h
>>>> +++ b/include/linux/percpu-refcount.h
>>>> @@ -210,15 +210,17 @@ static inline void percpu_ref_get(struct percpu_ref *ref)
>>>>  }
>>>>  
>>>>  /**
>>>> - * percpu_ref_tryget - try to increment a percpu refcount
>>>> + * percpu_ref_tryget_many - try to increment a percpu refcount
>>>>   * @ref: percpu_ref to try-get
>>>> + * @nr: number of references to get
>>>>   *
>>>>   * Increment a percpu refcount unless its count already reached zero.
>>>>   * Returns %true on success; %false on failure.
> 
> Minor nit: would be nice to change this so the two don't have identical
> comments. (eg: Increment a percpu refcount by @nr unless...)
>>>>   *
>>>>   * This function is safe to call as long as @ref is between init and exit.
>>>>   */
>>>> -static inline bool percpu_ref_tryget(struct percpu_ref *ref)
>>>> +static inline bool percpu_ref_tryget_many(struct percpu_ref *ref,
>>>> +					  unsigned long nr)
>>>>  {
>>>>  	unsigned long __percpu *percpu_count;
>>>>  	bool ret;
>>>> @@ -226,10 +228,10 @@ static inline bool percpu_ref_tryget(struct percpu_ref *ref)
>>>>  	rcu_read_lock();
>>>>  
>>>>  	if (__ref_is_percpu(ref, &percpu_count)) {
>>>> -		this_cpu_inc(*percpu_count);
>>>> +		this_cpu_add(*percpu_count, nr);
>>>>  		ret = true;
>>>>  	} else {
>>>> -		ret = atomic_long_inc_not_zero(&ref->count);
>>>> +		ret = atomic_long_add_unless(&ref->count, nr, 0);
>>>>  	}
>>>>  
>>>>  	rcu_read_unlock();
>>>> @@ -237,6 +239,20 @@ static inline bool percpu_ref_tryget(struct percpu_ref *ref)
>>>>  	return ret;
>>>>  }
>>>>  
>>>> +/**
>>>> + * percpu_ref_tryget - try to increment a percpu refcount
>>>> + * @ref: percpu_ref to try-get
>>>> + *
>>>> + * Increment a percpu refcount unless its count already reached zero.
>>>> + * Returns %true on success; %false on failure.
>>>> + *
>>>> + * This function is safe to call as long as @ref is between init and exit.
>>>> + */
>>>> +static inline bool percpu_ref_tryget(struct percpu_ref *ref)
>>>> +{
>>>> +	return percpu_ref_tryget_many(ref, 1);
>>>> +}
>>>> +
>>>>  /**
>>>>   * percpu_ref_tryget_live - try to increment a live percpu refcount
>>>>   * @ref: percpu_ref to try-get
>>>>
>>>
>>>
>>> -- 
>>> Jens Axboe
>>>
>>
>> -- 
>> tejun
> 
> Acked-by: Dennis Zhou <dennis@kernel.org>
> 
> Thanks,
> Dennis
> 

-- 
Pavel Begunkov


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  reply index

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-17 22:28 [PATCH 0/2] optimise ctx's refs grabbing in io_uring Pavel Begunkov
2019-12-17 22:28 ` [PATCH 1/2] pcpu_ref: add percpu_ref_tryget_many() Pavel Begunkov
2019-12-17 23:42   ` Jens Axboe
2019-12-18 16:26     ` Tejun Heo
2019-12-18 17:49       ` Dennis Zhou
2019-12-21 15:36         ` Pavel Begunkov [this message]
2019-12-17 22:28 ` [PATCH 2/2] io_uring: batch getting pcpu references Pavel Begunkov
2019-12-17 23:21   ` Jens Axboe
2019-12-17 23:31     ` Jens Axboe
2019-12-18  9:25       ` Pavel Begunkov
2019-12-18  9:23     ` Pavel Begunkov
2019-12-18  0:02   ` Jens Axboe
2019-12-18 10:41     ` Pavel Begunkov
2019-12-21 16:15   ` [PATCH v2 0/3] optimise ctx's refs grabbing in io_uring Pavel Begunkov
2019-12-21 16:15     ` [PATCH v2 1/3] pcpu_ref: add percpu_ref_tryget_many() Pavel Begunkov
2019-12-21 16:15     ` [PATCH v2 2/3] io_uring: batch getting pcpu references Pavel Begunkov
2019-12-21 16:15     ` [PATCH RFC v2 3/3] io_uring: batch get(ctx->ref) across submits Pavel Begunkov
2019-12-21 16:20       ` Pavel Begunkov
2019-12-21 16:38         ` Jens Axboe
2019-12-21 16:48           ` Pavel Begunkov
2019-12-21 17:01             ` Jens Axboe
2019-12-21 17:26               ` Pavel Begunkov
2019-12-21 20:12       ` [PATCH v3 0/2] optimise ctx's refs grabbing in io_uring Pavel Begunkov
2019-12-21 20:12         ` [PATCH v3 1/2] pcpu_ref: add percpu_ref_tryget_many() Pavel Begunkov
2019-12-21 20:12         ` [PATCH v3 2/2] io_uring: batch getting pcpu references Pavel Begunkov
2019-12-21 21:56           ` Pavel Begunkov
2019-12-28 11:13         ` [PATCH v4 0/2] optimise ctx's refs grabbing in io_uring Pavel Begunkov
2019-12-28 11:13           ` [PATCH v4 1/2] pcpu_ref: add percpu_ref_tryget_many() Pavel Begunkov
2019-12-28 11:13           ` [PATCH v4 2/2] io_uring: batch getting pcpu references Pavel Begunkov
2019-12-28 11:15             ` Pavel Begunkov
2019-12-28 17:03               ` Jens Axboe
2019-12-28 18:37                 ` Pavel Begunkov
2019-12-30  3:33                   ` Brian Gianforcaro
2019-12-30 18:45                     ` Pavel Begunkov

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