Re: [PATCH v2 10/10] ext4: correct some stale comment of criteria

[Kemeng Shi <shikemeng@huaweicloud.com>]

on 7/26/2023 10:50 PM, Ojaswin Mujoo wrote:
> On Wed, Jul 26, 2023 at 02:51:06AM +0800, Kemeng Shi wrote:
>> We named criteria with CR_XXX, correct stale comment to criteria with
>> raw number.
> 
> Hi Kemeng,
> 
> Thanks for the cleanups.
> 
>>
>> Fixes: f52f3d2b9fba ("ext4: Give symbolic names to mballoc criterias")
>> Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
>> Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
>> ---
>>  fs/ext4/mballoc.c | 8 ++++----
>>  1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
>> index 36eea63eaace..de5da76e6748 100644
>> --- a/fs/ext4/mballoc.c
>> +++ b/fs/ext4/mballoc.c
>> @@ -2777,8 +2777,8 @@ ext4_mb_regular_allocator(struct ext4_allocation_context *ac)
>>  
>>  	/*
>>  	 * ac->ac_2order is set only if the fe_len is a power of 2
>> -	 * if ac->ac_2order is set we also set criteria to 0 so that we
>> -	 * try exact allocation using buddy.
>> +	 * if ac->ac_2order is set we also set criteria to CR_POWER2_ALIGNED
>> +	 * so that we try exact allocation using buddy.
>>  	 */
>>  	i = fls(ac->ac_g_ex.fe_len);
>>  	ac->ac_2order = 0;
>> @@ -2835,8 +2835,8 @@ ext4_mb_regular_allocator(struct ext4_allocation_context *ac)
>>  			/*
>>  			 * Batch reads of the block allocation bitmaps
>>  			 * to get multiple READs in flight; limit
>> -			 * prefetching at cr=0/1, otherwise mballoc can
>> -			 * spend a lot of time loading imperfect groups
>> +			 * prefetching at cr below CR_FAST, otherwise mballoc
> 
> One of my earlier patchset has replaced the CR_FAST macro with
> ext4_mb_cr_expensive() so maybe we can account for that here:
> 
> https://lore.kernel.org/linux-ext4/20230630085927.140137-1-ojaswin@linux.ibm.com/
> 
Hi Ojaswin, sorry for missing this. I still could not find the comment update
of stale comment "limit prefetching at cr=0/1" in that patch. Maybe we could
update comment to "prefetching at inexpensive CR, otherwise ...". What do
you think. Or did I miss anything.

-- 
Best wishes
Kemeng Shi
> Regards,
> ojaswin
> 
>> +			 * can spend a lot of time loading imperfect groups
> 
>>  			 */
>>  			if ((prefetch_grp == group) &&
>>  			    (cr >= CR_FAST ||
>> -- 
>> 2.30.0
>>
>