Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S937302Ab3DIJxR (ORCPT ); Tue, 9 Apr 2013 05:53:17 -0400 Received: from mail-vb0-f53.google.com ([209.85.212.53]:63173 "EHLO mail-vb0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935236Ab3DIJxP (ORCPT ); Tue, 9 Apr 2013 05:53:15 -0400 MIME-Version: 1.0 In-Reply-To: References: <91239cde99aaba2715f63db1f88241d9f4a36e13.1364740180.git.viresh.kumar@linaro.org> <20130331181931.GA7533@htj.dyndns.org> Date: Tue, 9 Apr 2013 15:23:14 +0530 Message-ID: Subject: Re: [PATCH V4 3/4] block: queue work on unbound wq From: Amit Kucheria To: Viresh Kumar Cc: Tejun Heo , Jens Axboe , Robin Randhawa , linux-rt-users@vger.kernel.org, Patch Tracking , Peter Zijlstra , Liviu Dudau , linux-kernel@vger.kernel.org, Steven Rostedt , Lists linaro-kernel , Steve Bannister , airlied@redhat.com, Arvind Chauhan , mingo@redhat.com, davem@davemloft.net, Charles Garcia-Tobin Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7340 Lines: 163 On Tue, Apr 9, 2013 at 1:00 PM, Viresh Kumar wrote: > On 31 March 2013 23:49, Tejun Heo wrote: >> So, let's please introduce a new flag to mark these workqueues, say, >> WQ_UNBOUND_FOR_POWER_SAVE or whatever (please come up with a better >> name) and provide a compile time switch with boot time override. > > Hi Tejun, > > I have written a patch to get this done and want to get that a some review > before touching other drivers and spamming LKML with other patches :) > > Here it is: > > From: Viresh Kumar > Date: Mon, 8 Apr 2013 16:45:40 +0530 > Subject: [PATCH] workqueues: Introduce new flag WQ_POWER_EFFICIENT for power > oriented workqueues > > Workqueues can be performance or power oriented. For performance we may want to > keep them running on a single cpu, so that it remains cache hot. For power we > can give scheduler the liberty to choose target cpu for running work handler. > > Later one (Power oriented WQ) can be achieved if the workqueue is allocated with Rephrase as "Power-efficient workqueues can be achieved..." > WQ_UNBOUND flag. To make this compile time configurable with boot time override > this patch adds in another flag WQ_POWER_EFFICIENT. This will be converted to > WQ_UNBOUND (on wq allocation) if CONFIG_WQ_POWER_EFFICIENT is enabled and > bootargs contain workqueue.power_efficient=1. It is unused otherwise and normal > behavior of WQ without this flag is expected. Addition of a new flag seems a bit excessive IMHO. Why can't we just set the UNBOUND flag when the wq_power_efficient module param is set? It would make the patch a lot simpler too. > CONFIG option is currently added under kernel/power/Kconfig and is looking for > relevant Kconfig file. > > Signed-off-by: Viresh Kumar > --- > Documentation/kernel-parameters.txt | 15 +++++++++++++++ > include/linux/workqueue.h | 3 +++ > kernel/power/Kconfig | 18 ++++++++++++++++++ > kernel/workqueue.c | 14 ++++++++++++++ > 4 files changed, 50 insertions(+) > > diff --git a/Documentation/kernel-parameters.txt > b/Documentation/kernel-parameters.txt > index 12c42a5..210e5fc 100644 > --- a/Documentation/kernel-parameters.txt > +++ b/Documentation/kernel-parameters.txt > @@ -3249,6 +3249,21 @@ bytes respectively. Such letter suffixes can > also be entirely omitted. > that this also can be controlled per-workqueue for > workqueues visible under /sys/bus/workqueue/. > > + workqueue.power_efficient > + Workqueues can be performance or power oriented. For > + performance we may want to keep them running on a single > + cpu, so that it remains cache hot. For power we can give > + scheduler the liberty to choose target cpu for running > + work handler. > + > + Later one (Power oriented WQ) can be achieved if the > + workqueue is allocated with WQ_UNBOUND flag. Enabling > + power_efficient boot param will convert > + WQ_POWER_EFFICIENT flag to WQ_UNBOUND on wq allocation. > + This requires CONFIG_WQ_POWER_EFFICIENT to be enabled. > + WQ_POWER_EFFICIENT is unused if power_efficient is not > + set in boot params. > + > x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of > default x2apic cluster mode on platforms > supporting x2apic. > diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h > index 1a53816..168b5be 100644 > --- a/include/linux/workqueue.h > +++ b/include/linux/workqueue.h > @@ -299,6 +299,9 @@ enum { > WQ_HIGHPRI = 1 << 4, /* high priority */ > WQ_CPU_INTENSIVE = 1 << 5, /* cpu instensive workqueue */ > WQ_SYSFS = 1 << 6, /* visible in sysfs, see wq_sysfs_register() */ > + WQ_POWER_EFFICIENT = 1 << 7, /* WQ_UNBOUND, for power > + * saving, if wq_power_efficient is > + * enabled. Unused otherwise. */ > > __WQ_DRAINING = 1 << 16, /* internal: workqueue is draining */ > __WQ_ORDERED = 1 << 17, /* internal: workqueue is ordered */ > diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig > index 5dfdc9e..8d62400 100644 > --- a/kernel/power/Kconfig > +++ b/kernel/power/Kconfig > @@ -263,6 +263,24 @@ config PM_GENERIC_DOMAINS > bool > depends on PM > > +config WQ_POWER_EFFICIENT > + bool "Workqueue allocated as UNBOUND for power efficiency" > + depends on PM > + help > + Workqueues can be performance or power oriented. For performance we > + may want to keep them running on a single cpu, so that it remains > + cache hot. For power we can give scheduler the liberty to choose > + target cpu for running work handler. > + > + Later one (Power oriented WQ) can be achieved if the workqueue is > + allocated with WQ_UNBOUND flag. Enabling power_efficient boot param > + will convert WQ_POWER_EFFICIENT flag to WQ_UNBOUND on wq allocation. > + This requires CONFIG_WQ_POWER_EFFICIENT to be enabled. > + WQ_POWER_EFFICIENT is unused if power_efficient is not set in boot > + params. > + > + If in doubt, say N. > + > config PM_GENERIC_DOMAINS_SLEEP > def_bool y > depends on PM_SLEEP && PM_GENERIC_DOMAINS > diff --git a/kernel/workqueue.c b/kernel/workqueue.c > index 1228fd7..590e333 100644 > --- a/kernel/workqueue.c > +++ b/kernel/workqueue.c > @@ -271,6 +271,11 @@ static cpumask_var_t *wq_numa_possible_cpumask; > static bool wq_disable_numa; > module_param_named(disable_numa, wq_disable_numa, bool, 0444); > > +#ifdef CONFIG_WQ_POWER_EFFICIENT > +static bool wq_power_efficient = 0; > +module_param_named(power_efficient, wq_power_efficient, bool, 0444); > +#endif > + > static bool wq_numa_enabled; /* unbound NUMA affinity enabled */ > > /* buf for wq_update_unbound_numa_attrs(), protected by CPU hotplug > exclusion */ > @@ -4085,6 +4090,15 @@ struct workqueue_struct > *__alloc_workqueue_key(const char *fmt, > struct workqueue_struct *wq; > struct pool_workqueue *pwq; > > + if (flags & WQ_POWER_EFFICIENT) { > + flags &= ~WQ_POWER_EFFICIENT; > + > +#ifdef CONFIG_WQ_POWER_EFFICIENT > + if (wq_power_efficient) > + flags |= WQ_UNBOUND; > +#endif > + } > + > /* allocate wq and format name */ > if (flags & WQ_UNBOUND) > tbl_size = wq_numa_tbl_len * sizeof(wq->numa_pwq_tbl[0]); > > _______________________________________________ > linaro-kernel mailing list > linaro-kernel@lists.linaro.org > http://lists.linaro.org/mailman/listinfo/linaro-kernel -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/