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Subject: Re: [PATCH V3 4/5] ext4: get discard out of jbd2 commit kthread
 contex
From:   Wang Jianchao <jianchao.wan9@gmail.com>
To:     Theodore Ts'o <tytso@mit.edu>
Cc:     linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org,
        adilger.kernel@dilger.ca
References: <20210724074124.25731-1-jianchao.wan9@gmail.com>
 <20210724074124.25731-5-jianchao.wan9@gmail.com> <YRV6qqZcsNBHZzyn@mit.edu>
 <65c6aa35-5e4c-a717-d1dc-8842e3ce0424@gmail.com>
Message-ID: <5a3e272a-0714-4d10-d260-fc716f9438f9@gmail.com>
Date:   Thu, 26 Aug 2021 16:58:26 +0800
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On 2021/8/26 3:51 PM, Wang Jianchao wrote:

>>
>>> @@ -3672,8 +3724,14 @@ int __init ext4_init_mballoc(void)
>>>  	if (ext4_free_data_cachep == NULL)
>>>  		goto out_ac_free;
>>>  
>>> +	ext4_discard_wq = alloc_workqueue("ext4discard", WQ_UNBOUND, 0);
>>> +	if (!ext4_discard_wq)
>>> +		goto out_free_data;
>>> +
>>
>>
>> Perhaps we should only allocate the workqueue when it's needed ---
>> e.g., when a file system is mounted or remounted with "-o discard"?
>>
>> Then in ext4_exit_malloc(), we only free it if ext4_discard_wq is
>> non-NULL.
>>
>> This would save a bit of memory on systems that wouldn't need the ext4
>> discard work queue.
> 
> Yes, it make sense to the system with pool memory

s/pool/poor  :)

> 
> Thanks so much
> Jianchao
> 
>>
>> 					- Ted
>>