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

[Hao Jia]

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