From: Herbert Xu <herbert@gondor.apana.org.au>
To: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: Steffen Klassert <steffen.klassert@secunet.com>,
Lai Jiangshan <jiangshanlai@gmail.com>,
Peter Zijlstra <peterz@infradead.org>, Tejun Heo <tj@kernel.org>,
linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 8/9] padata: unbind parallel jobs from specific CPUs
Date: Thu, 22 Aug 2019 14:13:40 +1000 [thread overview]
Message-ID: <20190822041340.GA590@gondor.apana.org.au> (raw)
In-Reply-To: <20190813005224.30779-9-daniel.m.jordan@oracle.com>
On Mon, Aug 12, 2019 at 08:52:23PM -0400, Daniel Jordan wrote:
>
> @@ -191,22 +184,25 @@ static struct padata_priv *padata_get_next(struct parallel_data *pd)
> padata = list_entry(reorder->list.next,
> struct padata_priv, list);
>
> - list_del_init(&padata->list);
> - atomic_dec(&pd->reorder_objects);
> + /*
> + * The check fails in the unlikely event that two or more
> + * parallel jobs have hashed to the same CPU and one of the
> + * later ones finishes first.
> + */
> + if (padata->seq_nr == pd->processed) {
> + list_del_init(&padata->list);
> + atomic_dec(&pd->reorder_objects);
Now that you've changed the test for whether there is work to be
done you also need to update the code at the end of padata_reorder
that checks whether there is work to do. Otherwise we can end up
in a busy loop that just wastes CPU cycles.
Cheers,
--
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
next prev parent reply other threads:[~2019-08-22 4:13 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-13 0:52 [PATCH 0/9] padata: use unbound workqueues for parallel jobs Daniel Jordan
2019-08-13 0:52 ` [PATCH 1/9] padata: allocate workqueue internally Daniel Jordan
2019-08-13 0:52 ` [PATCH 2/9] workqueue: unconfine alloc/apply/free_workqueue_attrs() Daniel Jordan
2019-08-13 0:52 ` [PATCH 3/9] workqueue: require CPU hotplug read exclusion for apply_workqueue_attrs Daniel Jordan
2019-08-13 0:52 ` [PATCH 4/9] padata: make padata_do_parallel find alternate callback CPU Daniel Jordan
2019-08-13 0:52 ` [PATCH 5/9] pcrypt: remove padata cpumask notifier Daniel Jordan
2019-08-13 0:52 ` [PATCH 6/9] padata, pcrypt: take CPU hotplug lock internally in padata_alloc_possible Daniel Jordan
2019-08-13 0:52 ` [PATCH 7/9] padata: use separate workqueues for parallel and serial work Daniel Jordan
2019-08-13 0:52 ` [PATCH 8/9] padata: unbind parallel jobs from specific CPUs Daniel Jordan
2019-08-22 4:13 ` Herbert Xu [this message]
2019-08-22 22:13 ` Daniel Jordan
2019-08-13 0:52 ` [PATCH 9/9] padata: remove cpu_index from the parallel_queue Daniel Jordan
2019-08-20 6:07 ` [PATCH 0/9] padata: use unbound workqueues for parallel jobs Steffen Klassert
2019-08-21 4:15 ` Daniel Jordan
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