linux-kernel - Re: [patch 20/25] debugobjects: Prepare kmem

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Message-ID: <a776760d-ece2-74b5-278d-d070450472a8@huawei.com>
Date: Sat, 12 Oct 2024 10:02:36 +0800
From: "Leizhen (ThunderTown)" <thunder.leizhen@...wei.com>
To: Thomas Gleixner <tglx@...utronix.de>, LKML <linux-kernel@...r.kernel.org>
CC: Waiman Long <longman@...hat.com>
Subject: Re: [patch 20/25] debugobjects: Prepare kmem_cache allocations for
 batching



On 2024/10/12 4:47, Thomas Gleixner wrote:
> On Thu, Oct 10 2024 at 16:40, Leizhen wrote:
>> On 2024/10/8 0:50, Thomas Gleixner wrote:
>>> +static bool kmem_alloc_batch(struct hlist_head *head, struct kmem_cache *cache, gfp_t gfp)
>>> +{
>>> +	struct hlist_node *last = NULL;
>>> +	struct debug_obj *obj;
>>> +
>>> +	for (int cnt = 0; cnt < ODEBUG_BATCH_SIZE; cnt++) {
>>> +		obj = kmem_cache_zalloc(cache, gfp);
>>> +		if (!obj) {
>>> +			free_object_list(head);
>>> +			return false;
>>> +		}
>>> +		debug_objects_allocated++;
>>> +
>>> +		if (!last)
>>> +			last = &obj->node;
>>> +		obj->batch_last = last;
>>> +
>>> +		hlist_add_head(&obj->node, head);
>>
>> There seems to be a need to use hlist_splice_init() outside the loop like patch 2/25.
>> Prepare the local list first, if all ODEBUG_BATCH_SIZE is successfully allocated,
>> attach it to 'head' at a time, including account debug_objects_allocated. Then back
>> to patch 8/25, keep debug_objects_freed still in lock protection and do not move it
>> into free_object_list(). Seems like it should be.
> 
> In case that the allocation of 16 object fails, the accounting
> concurrency problem vs. free_object_list is pretty irrelevant.
> 
> It's debug information and moving it under lock protection for a corner
> case is just making the code more complex.

OK, got it, with 8/25.

> 
> Thanks,
> 
>         tglx
> 
> .
> 

-- 
Regards,
  Zhen Lei