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Message-ID: <ZmybGZDbXkw7JTjc@zx2c4.com>
Date: Fri, 14 Jun 2024 21:33:45 +0200
From: "Jason A. Donenfeld" <Jason@...c4.com>
To: Uladzislau Rezki <urezki@...il.com>
Cc: "Paul E. McKenney" <paulmck@...nel.org>,
Vlastimil Babka <vbabka@...e.cz>, Jakub Kicinski <kuba@...nel.org>,
Julia Lawall <Julia.Lawall@...ia.fr>, linux-block@...r.kernel.org,
kernel-janitors@...r.kernel.org, bridge@...ts.linux.dev,
linux-trace-kernel@...r.kernel.org,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
kvm@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
"Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>,
Christophe Leroy <christophe.leroy@...roup.eu>,
Nicholas Piggin <npiggin@...il.com>, netdev@...r.kernel.org,
wireguard@...ts.zx2c4.com, linux-kernel@...r.kernel.org,
ecryptfs@...r.kernel.org, Neil Brown <neilb@...e.de>,
Olga Kornievskaia <kolga@...app.com>, Dai Ngo <Dai.Ngo@...cle.com>,
Tom Talpey <tom@...pey.com>, linux-nfs@...r.kernel.org,
linux-can@...r.kernel.org, Lai Jiangshan <jiangshanlai@...il.com>,
netfilter-devel@...r.kernel.org, coreteam@...filter.org
Subject: Re: [PATCH 00/14] replace call_rcu by kfree_rcu for simple
kmem_cache_free callback
On Fri, Jun 14, 2024 at 02:35:33PM +0200, Uladzislau Rezki wrote:
> + /* Should a destroy process be deferred? */
> + if (s->flags & SLAB_DEFER_DESTROY) {
> + list_move_tail(&s->list, &slab_caches_defer_destroy);
> + schedule_delayed_work(&slab_caches_defer_destroy_work, HZ);
> + goto out_unlock;
> + }
Wouldn't it be smoother to have the actual kmem_cache_free() function
check to see if it's been marked for destruction and the refcount is
zero, rather than polling every one second? I mentioned this approach
in: https://lore.kernel.org/all/Zmo9-YGraiCj5-MI@zx2c4.com/ -
I wonder if the right fix to this would be adding a `should_destroy`
boolean to kmem_cache, which kmem_cache_destroy() sets to true. And
then right after it checks `if (number_of_allocations == 0)
actually_destroy()`, and likewise on each kmem_cache_free(), it
could check `if (should_destroy && number_of_allocations == 0)
actually_destroy()`.
Jason
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