From: Chris Metcalf <cmetcalf@tilera.com>
To: Michal Hocko <mhocko@suse.cz>, Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: linux-kernel@vger.kernel.org, akpm@linux-foundation.org,
Mel Gorman <mgorman@suse.de>, Tejun Heo <tj@kernel.org>,
Christoph Lameter <cl@gentwo.org>,
Frederic Weisbecker <fweisbec@gmail.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Rik van Riel <riel@redhat.com>, Jianyu Zhan <nasa4836@gmail.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Khalid Aziz <khalid.aziz@oracle.com>,
linux-mm@kvack.org, Gilad Ben-Yossef <gilad@benyossef.com>
Subject: Re: [PATCH] swap: remove the struct cpumask has_work
Date: Thu, 31 Jul 2014 12:09:19 -0400 [thread overview]
Message-ID: <53DA6A2F.100@tilera.com> (raw)
In-Reply-To: <20140731115137.GA20244@dhcp22.suse.cz>
On 7/31/2014 7:51 AM, Michal Hocko wrote:
> On Thu 31-07-14 11:30:19, Lai Jiangshan wrote:
>> It is suggested that cpumask_var_t and alloc_cpumask_var() should be used
>> instead of struct cpumask. But I don't want to add this complicity nor
>> leave this unwelcome "static struct cpumask has_work;", so I just remove
>> it and use flush_work() to perform on all online drain_work. flush_work()
>> performs very quickly on initialized but unused work item, thus we don't
>> need the struct cpumask has_work for performance.
> Why? Just because there is general recommendation for using
> cpumask_var_t rather than cpumask?
>
> In this particular case cpumask shouldn't matter much as it is static.
> Your code will work as well, but I do not see any strong reason to
> change it just to get rid of cpumask which is not on stack.
The code uses for_each_cpu with a cpumask to avoid waking cpus that don't
need to do work. This is important for the nohz_full type functionality,
power efficiency, etc. So, nack for this change.
--
Chris Metcalf, Tilera Corp.
http://www.tilera.com
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next prev parent reply other threads:[~2014-07-31 16:09 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-31 3:30 [PATCH] swap: remove the struct cpumask has_work Lai Jiangshan
2014-07-31 11:51 ` Michal Hocko
2014-07-31 16:09 ` Chris Metcalf [this message]
2014-08-01 1:39 ` Lai Jiangshan
2014-08-01 17:16 ` Chris Metcalf
2014-08-01 17:28 ` Frederic Weisbecker
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