linux-kernel - Re: [PATCH 2/2] drm/amdkfd: Slighly optimize 'init_doorbell

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Message-ID: <306b774e-6ee7-c976-a303-f566f7ba626c@wanadoo.fr>
Date:   Tue, 23 Nov 2021 07:02:28 +0100
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     Felix Kuehling <felix.kuehling@....com>, alexander.deucher@....com,
        christian.koenig@....com, Xinhui.Pan@....com, airlied@...ux.ie,
        daniel@...ll.ch
Cc:     amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH 2/2] drm/amdkfd: Slighly optimize 'init_doorbell_bitmap()'

Le 22/11/2021 à 22:44, Felix Kuehling a écrit :
> Am 2021-11-21 um 12:41 p.m. schrieb Christophe JAILLET:
>> The 'doorbell_bitmap' bitmap has just been allocated. So we can use the
>> non-atomic '__set_bit()' function to save a few cycles as no concurrent
>> access can happen.
>>
>> Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
> 
> Thank you for the patches. I think the same sort of change (at least the
> allocation/freeing part) could be applied to the queue_slot_bitmap in
> kfd_process_queue_manager.c. Would you like to submit another revision
> of this patch series that handles that as well?

I'll send a v2 which will fix the missing ',' spotted by the kernel test 
robot and include kfd_process_queue_manager.c.

All my patches are compile tested (otherwise it is said bellow the ---). 
Looks like I missed this one :(.

CJ

> 
> Either way, this series is
> 
> Reviewed-by: Felix Kuehling <Felix.Kuehling@....com>
> 
> 
>> ---
>> bitmap_set() could certainly also be use, but range checking would be
>> tricky.
>> ---
>>   drivers/gpu/drm/amd/amdkfd/kfd_process.c | 6 +++---
>>   1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_process.c b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
>> index 172ee8763523..2e9d341062c4 100644
>> --- a/drivers/gpu/drm/amd/amdkfd/kfd_process.c
>> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
>> @@ -1447,9 +1447,9 @@ static int init_doorbell_bitmap(struct qcm_process_device *qpd,
>>   
>>   	for (i = 0; i < KFD_MAX_NUM_OF_QUEUES_PER_PROCESS / 2; i++) {
>>   		if (i >= range_start && i <= range_end) {
>> -			set_bit(i, qpd->doorbell_bitmap);
>> -			set_bit(i + KFD_QUEUE_DOORBELL_MIRROR_OFFSET,
>> -				qpd->doorbell_bitmap);
>> +			__set_bit(i, qpd->doorbell_bitmap);
>> +			__set_bit(i + KFD_QUEUE_DOORBELL_MIRROR_OFFSET,
>> +				  qpd->doorbell_bitmap);
>>   		}
>>   	}
>>   
>