From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 22FF01F8AE5 for ; Wed, 19 Feb 2025 15:59:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739980779; cv=none; b=AE3lgYpnN+CK+TcNoul6aL8Pf5vrEXC7tyFzQniuo3PZX778snuMCLcV9ccKojoRONmYghYW5Xfr38Gv+qW4P+FD01v3Xc9qnj46h26Ra8pnQnDeFX/am12FTzg1qZJmfQ05tebtqtPexrtUT6usKxY27z7KuSDNo7n7o5csT6U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739980779; c=relaxed/simple; bh=EytW1lFPKATO0gNl3E/Jw87TvBaSDCpj51b4vRxBcCY=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=CJCWV0da4C/K6qSiTibmyi1HWikVU4CPlNwZKjRO56n5n/QrFoEizyLOz39rXNqJ8yxS1I8bOBFwJKe+lEEBzGcVA6Y6f9rhT/nqrzIp+A/rsaEPLpIvpEgt1NKN9BZUlUHdDW8xlEp0SIygdAlOtAhct0DetuVqitWRJWygNFw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id BA3291682; Wed, 19 Feb 2025 07:59:54 -0800 (PST) Received: from [10.1.35.44] (e127648.arm.com [10.1.35.44]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 0893B3F6A8; Wed, 19 Feb 2025 07:59:32 -0800 (PST) Message-ID: <5ff60151-cb77-46b7-ad52-813981c99d26@arm.com> Date: Wed, 19 Feb 2025 15:59:30 +0000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/2] sched/uclamp: Add uclamp_is_used() check before enable it To: Xuewen Yan , vincent.guittot@linaro.org, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com Cc: dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, hongyan.xia2@arm.com, ke.wang@unisoc.com, di.shen@unisoc.com, xuewen.yan94@gmail.com, linux-kernel@vger.kernel.org References: <20250219093747.2612-1-xuewen.yan@unisoc.com> <20250219093747.2612-2-xuewen.yan@unisoc.com> Content-Language: en-US From: Christian Loehle In-Reply-To: <20250219093747.2612-2-xuewen.yan@unisoc.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 2/19/25 09:37, Xuewen Yan wrote: > Because the static_branch_enable() would get the cpus_read_lock(), > and sometimes users may frequently set the uclamp value of tasks, > and this operation would call the static_branch_enable() > frequently, so add the uclamp_is_used() check to prevent calling > the cpus_read_lock() frequently. > And to make the code more concise, add a helper function to encapsulate > this and use it everywhere we enable sched_uclamp_used. > > Signed-off-by: Xuewen Yan > --- > V2: > - change some commit message; > - Add a helper function and use it everywhere when enable uclamp (Vincent) > --- > --- > kernel/sched/core.c | 6 +++--- > kernel/sched/sched.h | 14 ++++++++++++++ > kernel/sched/syscalls.c | 2 +- > 3 files changed, 18 insertions(+), 4 deletions(-) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 38a7192bfc19..0466a2f61b99 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -1942,12 +1942,12 @@ static int sysctl_sched_uclamp_handler(const struct ctl_table *table, int write, > } > > if (update_root_tg) { > - static_branch_enable(&sched_uclamp_used); > + sched_uclamp_enable(); > uclamp_update_root_tg(); > } > > if (old_min_rt != sysctl_sched_uclamp_util_min_rt_default) { > - static_branch_enable(&sched_uclamp_used); > + sched_uclamp_enable(); > uclamp_sync_util_min_rt_default(); > } > > @@ -9295,7 +9295,7 @@ static ssize_t cpu_uclamp_write(struct kernfs_open_file *of, char *buf, > if (req.ret) > return req.ret; > > - static_branch_enable(&sched_uclamp_used); > + sched_uclamp_enable(); > > guard(mutex)(&uclamp_mutex); > guard(rcu)(); > diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h > index 3624fdce5536..bd22af347d0b 100644 > --- a/kernel/sched/sched.h > +++ b/kernel/sched/sched.h > @@ -3407,6 +3407,18 @@ static inline bool uclamp_is_used(void) > return static_branch_likely(&sched_uclamp_used); > } > > +/* > + * Enabling static branches would get the cpus_read_lock(), > + * check whether uclamp_is_used before enable it to avoid always > + * calling cpus_read_lock(). Because we never disable this > + * static key once enable it. > + */ > +static inline void sched_uclamp_enable(void) > +{ > + if (!uclamp_is_used()) > + static_branch_enable(&sched_uclamp_used); > +} > + Reviewed-by > static inline unsigned long uclamp_rq_get(struct rq *rq, > enum uclamp_id clamp_id) > { > @@ -3486,6 +3498,8 @@ static inline bool uclamp_is_used(void) > return false; > } > > +static inline void sched_uclamp_enable(void) {} > + > static inline unsigned long > uclamp_rq_get(struct rq *rq, enum uclamp_id clamp_id) > { > diff --git a/kernel/sched/syscalls.c b/kernel/sched/syscalls.c > index 456d339be98f..9100a77e9d79 100644 > --- a/kernel/sched/syscalls.c > +++ b/kernel/sched/syscalls.c > @@ -368,7 +368,7 @@ static int uclamp_validate(struct task_struct *p, > * blocking operation which obviously cannot be done while holding > * scheduler locks. > */ > - static_branch_enable(&sched_uclamp_used); > + sched_uclamp_enable(); > > return 0; > } Reviewed-by: Christian Loehle