From: Aleksa Sarai <cyphar@cyphar.com>
To: Tejun Heo <tj@kernel.org>
Cc: "Peter Zijlstra" <peterz@infradead.org>,
lizefan@huawei.com, mingo@redhat.com, richard@nod.at,
"Frédéric Weisbecker" <fweisbec@gmail.com>,
linux-kernel@vger.kernel.org, cgroups@vger.kernel.org
Subject: Re: [PATCH v10 1/4] cgroups: use bitmask to filter for_each_subsys
Date: Mon, 27 Apr 2015 02:05:47 +1000 [thread overview]
Message-ID: <CAOviyagvVTKjRp4wxyNo4Oke-w=Wbda+UyHAN-ih9yFX-8jqmw@mail.gmail.com> (raw)
In-Reply-To: <20150422160258.GE10738@htj.duckdns.org>
Hey,
>> > > static struct cftype cgroup_dfl_base_files[];
>> > > +#define for_each_subsys_which(ss_mask, ss, ssid) \
>> > > + for_each_subsys((ss), (ssid)) \
>> > > + if ((ss_mask) & (1 << (ssid)))
>> >
>> > Maybe using for_each_set_bit() is better?
>> >
>> > #define for_each_subsys_which(ss_mask, ss, ssid) \
>> > for_each_set_bit(ssid, &(ss_mask), CGROUP_SUBSYS_COUNT) \
>> > if ((ss) = group_subsys[ssid] && false) \
>> > ; \
>> > else
>>
>> Clever that ;-)
>
> Thanks. It kinda bothers me that for_each_set_bit() doesn't collapse
> to combo of ffs() + clearing bit off of a temp mask when size is const
> and <= ulong, which would be quite a bit lighter. Right now it'd be
> calling into generic find_first/next_bit() functions unconditionally.
> Ah well, it can be optimized later.
This macro causes issues with lines like:
for_each_subsys_which(ss, ssid, ~cgrp_dfl_root_inhibit_ss_mask)
In addition, there are a bunch of cgroup_* functions that use unsigned
ints for bitops (cgroup_calc_child_subsys_mask, rebind_subsystems,
cgroup_print_ss_mask). Is there a better solution to this problem, or
should I just switch back to my naive solution?
--
Aleksa Sarai (cyphar)
www.cyphar.com
next prev parent reply other threads:[~2015-04-26 16:05 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-19 12:22 [PATCH v10 0/4] cgroups: add pids subsystem Aleksa Sarai
2015-04-19 12:22 ` [PATCH v10 1/4] cgroups: use bitmask to filter for_each_subsys Aleksa Sarai
2015-04-22 15:25 ` Tejun Heo
2015-04-22 15:42 ` Peter Zijlstra
2015-04-22 16:02 ` Tejun Heo
2015-04-26 16:05 ` Aleksa Sarai [this message]
2015-04-26 16:09 ` Tejun Heo
2015-05-13 5:44 ` Aleksa Sarai
2015-05-13 13:50 ` Tejun Heo
2015-04-22 15:30 ` Tejun Heo
2015-04-19 12:22 ` [PATCH v10 2/4] cgroups: replace explicit ss_mask checking with for_each_subsys_which Aleksa Sarai
2015-04-22 15:31 ` Tejun Heo
2015-04-19 12:22 ` [PATCH v10 3/4] cgroups: allow a cgroup subsystem to reject a fork Aleksa Sarai
2015-04-22 15:54 ` Tejun Heo
2015-04-24 13:59 ` Aleksa Sarai
2015-04-24 15:48 ` Tejun Heo
2015-05-14 10:57 ` Aleksa Sarai
2015-05-14 15:08 ` Tejun Heo
2015-04-19 12:22 ` [PATCH v10 4/4] cgroups: implement the PIDs subsystem Aleksa Sarai
2015-04-22 16:29 ` Tejun Heo
2015-04-23 0:43 ` Aleksa Sarai
2015-04-24 15:36 ` Tejun Heo
2015-05-13 17:04 ` Aleksa Sarai
2015-05-13 17:29 ` Tejun Heo
2015-05-13 17:44 ` Aleksa Sarai
2015-05-13 17:47 ` Tejun Heo
2015-05-16 3:59 ` Aleksa Sarai
2015-05-18 1:24 ` Tejun Heo
2015-04-24 14:24 ` Aleksa Sarai
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