Re: [PATCH v5 2/6] mm/zswap: Support batch writeback in shrink_memcg()

[Hao Jia <jiahao.kernel@gmail.com>]

On 2026/6/30 08:21, Yosry Ahmed wrote:
> On Mon, Jun 29, 2026 at 07:20:28PM +0800, Hao Jia wrote:

>>   
>>   static void shrink_worker(struct work_struct *w)
>>   {
>>   	struct mem_cgroup *memcg;
>> -	int ret, failures = 0, attempts = 0;
>> +	int failures = 0, attempts = 0;
>>   	unsigned long thr;
>> +	long ret;
>>   
>>   	/* Reclaim down to the accept threshold */
>>   	thr = zswap_accept_thr_pages();
>> @@ -1373,7 +1422,7 @@ static void shrink_worker(struct work_struct *w)
>>   			goto resched;
>>   		}
>>   
>> -		ret = shrink_memcg(memcg);
>> +		ret = shrink_memcg(memcg, NR_ZSWAP_WB_BATCH);
>>   		/* drop the extra reference */
>>   		mem_cgroup_put(memcg);
>>   
>> @@ -1394,7 +1443,7 @@ static void shrink_worker(struct work_struct *w)
>>   		}
>>   		++attempts;
>>   
>> -		if (ret && ++failures == MAX_RECLAIM_RETRIES)
>> +		if (ret <= 0 && ++failures == MAX_RECLAIM_RETRIES)
>>   			break;
>>   resched:
>>   		cond_resched();
>> @@ -1504,7 +1553,7 @@ bool zswap_store(struct folio *folio)
>>   	objcg = get_obj_cgroup_from_folio(folio);
>>   	if (objcg && !obj_cgroup_may_zswap(objcg)) {
>>   		memcg = get_mem_cgroup_from_objcg(objcg);
>> -		if (shrink_memcg(memcg)) {
>> +		if (shrink_memcg(memcg, num_node_state(N_NORMAL_MEMORY)) <= 0) {
> 
> Why not just 1?
> 
> I guess the current behavior will try each node. But this doesn't really
> match it, as we may reclaim everything from the first node. Right?
> 

Yes, it just keeps the number the same as before, but the behavior is 
not exactly the same.

> I think it's probably fine to just do 1 here, fairness is not the main
> concern in this code path, we're really just trying to free up some
> space to free up some space for the incoming page. I doubt these limits
> are actually being used extensively anyway, so we can revisit this later
> if needed.

Okay, I'll do this in the next version.

Thanks,
Hao
> 
>>   			mem_cgroup_put(memcg);
>>   			goto put_objcg;
>>   		}
>> -- 
>> 2.34.1
>>