linux-kernel - Re: [PATCH v5 01/14] slab: add opt-in caching layer of percpu sheaves

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Message-ID: <446b0ed2-16e5-45fa-82a1-09ed99108558@suse.cz>
Date: Tue, 26 Aug 2025 10:03:30 +0200
From: Vlastimil Babka <vbabka@...e.cz>
To: Harry Yoo <harry.yoo@...cle.com>
Cc: Suren Baghdasaryan <surenb@...gle.com>,
 "Liam R. Howlett" <Liam.Howlett@...cle.com>,
 Christoph Lameter <cl@...two.org>, David Rientjes <rientjes@...gle.com>,
 Roman Gushchin <roman.gushchin@...ux.dev>,
 Uladzislau Rezki <urezki@...il.com>, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, rcu@...r.kernel.org,
 maple-tree@...ts.infradead.org
Subject: Re: [PATCH v5 01/14] slab: add opt-in caching layer of percpu sheaves

On 8/18/25 12:09, Harry Yoo wrote:
>> +alloc_empty:
>> +	local_unlock(&s->cpu_sheaves->lock);
>> +
>> +	empty = alloc_empty_sheaf(s, GFP_NOWAIT);
>> +	if (empty)
>> +		goto got_empty;
>> +
>> +	if (put_fail)
>> +		 stat(s, BARN_PUT_FAIL);
>> +
>> +	if (!sheaf_flush_main(s))
>> +		return NULL;
>> +
>> +	if (!local_trylock(&s->cpu_sheaves->lock))
>> +		return NULL;
>> +
>> +	/*
>> +	 * we flushed the main sheaf so it should be empty now,
>> +	 * but in case we got preempted or migrated, we need to
>> +	 * check again
>> +	 */
>> +	if (pcs->main->size == s->sheaf_capacity)
>> +		goto restart;
> 
> I think it's missing:
> 
> pcs = this_cpu_ptr(&s->cpu_sheaves);
> 
> between local_trylock() and reading pcs->main->size().

Oops, yes, thanks!
Also fixed up the other things you pointed out.