From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f170.google.com (mail-pl1-f170.google.com [209.85.214.170]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 57E1317B50B for ; Thu, 6 Mar 2025 21:47:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.170 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741297670; cv=none; b=DGINijffm06xtKPGMmjQ4A0B175eB5VNBXToGrWoAKdcaQ4vocmCfN6NRryEhJkm3bwpUVEmXW/mk3w1MXWP/eAGdcIDO12NZMe0+F3BKkh1R7cFBAjhSQMWVgBivjxOYH2erp+CTh2Ken+ef7z9j0MxGkHZFwF/4dL7eDVDKKo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741297670; c=relaxed/simple; bh=cH9Hq7WQ5/zsdr0tUWmk3KoiT3Q/pLhW6KUfARagBdk=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=qa8TeylKWfg4DnEARCfEq6VkJJ/Vsnr1J2rMVk4HreJx4uDVDFB8kyQ2Hkx6bAyin2qSZ/rUaz6y5UeJ+QLzzKwD2N/PQif106OH+qSlXW+B9UuEX0H7RaHPLhdqfhcXty/Z5SYHDp9Mdb8gDhmRoACNTwRusRYPg9MkVuSen3U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=Q0sJp75Z; arc=none smtp.client-ip=209.85.214.170 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Q0sJp75Z" Received: by mail-pl1-f170.google.com with SMTP id d9443c01a7336-2235189adaeso19986945ad.0 for ; Thu, 06 Mar 2025 13:47:49 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1741297668; x=1741902468; darn=vger.kernel.org; h=content-transfer-encoding:in-reply-to:from:content-language :references:cc:to:subject:user-agent:mime-version:date:message-id :from:to:cc:subject:date:message-id:reply-to; bh=t9a0dAVL/AZWOUQR/lGFl+t00mrO/OYf4dYWFlvsLAw=; b=Q0sJp75Z+slO/DkO+04Lw1UkL1FXcXnBY5iqeDCmOHk1n1R9aeeVrC4OD7La2Kd9rc c4tUuYdiD2gKzaaldCfuh1eUy370l9LaWjlmf7pvXr2nq7MWGk9UYOIfHEoeTJjKzq2H XSi0Oq8Qr0+kHZM4eI97Nm2VymKQo+13dOak9rvrJ3QVPQkvZLa/zfiDSZmySMYqqASn v9YypYwJ5In3m4iHM/wvvhM40HEAQQpdHtJ/62ddjbE2jNQe1ZgTJZpOWDcF5qB6Y9rJ VSZHCj2f7g2I8DEAljmIKkhsIfCu0MxFD9ccOBF6t7bfk/IeahOsHyZlEuK7//Jp4psy go9g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1741297668; x=1741902468; h=content-transfer-encoding:in-reply-to:from:content-language :references:cc:to:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=t9a0dAVL/AZWOUQR/lGFl+t00mrO/OYf4dYWFlvsLAw=; b=rcyI7w57qKk4zR1Oug5CHH67Y+yFgH1a6hTRPGYKaXnauJ6lBabswcJkVZDE0aXE3q RpG0ncfpJf/HD0MMsktKIX7HR5QQ43+SFRz7pdQ3iJKWPrrAVNaX7eBLYM6nJIASk0M4 oUBF4b79GdRnZsJZzu2prnZJgqrFxPoRXf/Qzoa5PHK+xvPBn4NbB+JNa1IO7qoNX8hU TAhQKGdgOwAccGTK2D2NcCEk+VePy38Zq/u534jKAxK6pOU2UFbn4ek3j0LynOK8B2fQ TFeWohuiLl3OpiUqVIQSNNlmGTq5II7s7a1xPsTKM8mSaKEoohcnx1FUMoolJFuzP2z1 t/MQ== X-Forwarded-Encrypted: i=1; AJvYcCViLK20uTTkHQ3pd25mZmmzbnxiVEfjDJUHasGHQ0//mQ/zm2ObVIep88h5jk3bNIzDHqr3cFEu@vger.kernel.org X-Gm-Message-State: AOJu0Yw4WquJWaLJ9qdmqzr5vVzdHQQQ0HSVEqYX0THBIshsCCqVtqDp U/MK7nb+wyx4KCxlSJJFSIjJ0mzete/oQDExhDmBllbxE7zS2oCGBV/3OQ== X-Gm-Gg: ASbGnct//3bqLjuUpD/SEQ+0VGbbVnPNu+0fkUefMhr+7BsqPVMLHe/A0Ttm53ir+lc frMIoB3GMSily1VzKvT5SnXcoEttBcm8ll6ALTsYMw2hJMREaRynGJHDDx9zIwkFCtwh6mRxaBv IrMZ1aI+mqXZ/IWh+rZsdq3M9S3wnEuxHyD022AujwVlOssEdHFlpUTO3kOj+ZJaABEUlYIYBVS 6pZQYOX5lQHPbogXNG1nC1JsaUOCCWQEvaS0cv7Kk3P+qufJ6ek856E2WPy39q1sfUBYq9QeqGB K2WxDgjH8Z4Gtuky5yfXSi1dEg3HRZImegA8FMRRS/d6N9MzAW6Ty2idrRH9StIbgWX2rS96Kaj / X-Google-Smtp-Source: AGHT+IGVGsKex96vDISYzZdtD1CF7FPmnf5XXQSJH1a6blsHvrz5J51CDUj3DDOuLRqv9alKaayf2A== X-Received: by 2002:a17:903:11d0:b0:21f:53a5:19e0 with SMTP id d9443c01a7336-22409404e15mr79186615ad.12.1741297668292; Thu, 06 Mar 2025 13:47:48 -0800 (PST) Received: from ?IPV6:2a03:83e0:1151:15:d431:c86b:892f:8e30? ([2620:10d:c090:500::6:d8b]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-224109ddcaesm17349635ad.28.2025.03.06.13.47.47 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 06 Mar 2025 13:47:47 -0800 (PST) Message-ID: Date: Thu, 6 Mar 2025 13:47:46 -0800 Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 3/4 v2] cgroup: separate rstat locks for subsystems To: Yosry Ahmed Cc: tj@kernel.org, shakeel.butt@linux.dev, mhocko@kernel.org, hannes@cmpxchg.org, akpm@linux-foundation.org, linux-mm@kvack.org, cgroups@vger.kernel.org, kernel-team@meta.com References: <20250227215543.49928-1-inwardvessel@gmail.com> <20250227215543.49928-4-inwardvessel@gmail.com> Content-Language: en-US From: JP Kobryn In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2/28/25 11:20 AM, Yosry Ahmed wrote: > On Thu, Feb 27, 2025 at 01:55:42PM -0800, inwardvessel wrote: >> From: JP Kobryn >> >> Let the existing locks be dedicated to the base stats and rename them as >> such. Also add new rstat locks for each enabled subsystem. When handling >> cgroup subsystem states, distinguish between formal subsystems (memory, >> io, etc) and the base stats subsystem state (represented by >> cgroup::self) to decide on which locks to take. This change is made to >> prevent contention between subsystems when updating/flushing stats. >> >> Signed-off-by: JP Kobryn >> --- >> kernel/cgroup/rstat.c | 93 +++++++++++++++++++++++++++++++++---------- >> 1 file changed, 72 insertions(+), 21 deletions(-) >> >> diff --git a/kernel/cgroup/rstat.c b/kernel/cgroup/rstat.c >> index 88908ef9212d..b3eaefc1fd07 100644 >> --- a/kernel/cgroup/rstat.c >> +++ b/kernel/cgroup/rstat.c >> @@ -9,8 +9,12 @@ >> >> #include >> >> -static DEFINE_SPINLOCK(cgroup_rstat_lock); >> -static DEFINE_PER_CPU(raw_spinlock_t, cgroup_rstat_cpu_lock); >> +static DEFINE_SPINLOCK(cgroup_rstat_base_lock); >> +static DEFINE_PER_CPU(raw_spinlock_t, cgroup_rstat_base_cpu_lock); >> + >> +static spinlock_t cgroup_rstat_subsys_lock[CGROUP_SUBSYS_COUNT]; >> +static DEFINE_PER_CPU(raw_spinlock_t, >> + cgroup_rstat_subsys_cpu_lock[CGROUP_SUBSYS_COUNT]); >> >> static void cgroup_base_stat_flush(struct cgroup *cgrp, int cpu); >> >> @@ -20,8 +24,13 @@ static struct cgroup_rstat_cpu *cgroup_rstat_cpu( >> return per_cpu_ptr(css->rstat_cpu, cpu); >> } >> >> +static inline bool is_base_css(struct cgroup_subsys_state *css) >> +{ >> + return css->ss == NULL; >> +} >> + >> /* >> - * Helper functions for rstat per CPU lock (cgroup_rstat_cpu_lock). >> + * Helper functions for rstat per CPU locks. >> * >> * This makes it easier to diagnose locking issues and contention in >> * production environments. The parameter @fast_path determine the >> @@ -36,12 +45,12 @@ unsigned long _cgroup_rstat_cpu_lock(raw_spinlock_t *cpu_lock, int cpu, >> bool contended; >> >> /* >> - * The _irqsave() is needed because cgroup_rstat_lock is >> - * spinlock_t which is a sleeping lock on PREEMPT_RT. Acquiring >> - * this lock with the _irq() suffix only disables interrupts on >> - * a non-PREEMPT_RT kernel. The raw_spinlock_t below disables >> - * interrupts on both configurations. The _irqsave() ensures >> - * that interrupts are always disabled and later restored. >> + * The _irqsave() is needed because the locks used for flushing are >> + * spinlock_t which is a sleeping lock on PREEMPT_RT. Acquiring this lock >> + * with the _irq() suffix only disables interrupts on a non-PREEMPT_RT >> + * kernel. The raw_spinlock_t below disables interrupts on both >> + * configurations. The _irqsave() ensures that interrupts are always >> + * disabled and later restored. >> */ >> contended = !raw_spin_trylock_irqsave(cpu_lock, flags); >> if (contended) { >> @@ -87,7 +96,7 @@ __bpf_kfunc void cgroup_rstat_updated( >> struct cgroup_subsys_state *css, int cpu) >> { >> struct cgroup *cgrp = css->cgroup; >> - raw_spinlock_t *cpu_lock = per_cpu_ptr(&cgroup_rstat_cpu_lock, cpu); >> + raw_spinlock_t *cpu_lock; >> unsigned long flags; >> >> /* >> @@ -101,6 +110,12 @@ __bpf_kfunc void cgroup_rstat_updated( >> if (data_race(cgroup_rstat_cpu(css, cpu)->updated_next)) >> return; >> >> + if (is_base_css(css)) >> + cpu_lock = per_cpu_ptr(&cgroup_rstat_base_cpu_lock, cpu); >> + else >> + cpu_lock = per_cpu_ptr(cgroup_rstat_subsys_cpu_lock, cpu) + >> + css->ss->id; >> + > > Maybe wrap this in a macro or function since it's used more than once. > >> flags = _cgroup_rstat_cpu_lock(cpu_lock, cpu, cgrp, true); >> >> /* put @css and all ancestors on the corresponding updated lists */ >> @@ -208,11 +223,17 @@ static struct cgroup_subsys_state *cgroup_rstat_updated_list( >> struct cgroup_subsys_state *root, int cpu) >> { >> struct cgroup *cgrp = root->cgroup; >> - raw_spinlock_t *cpu_lock = per_cpu_ptr(&cgroup_rstat_cpu_lock, cpu); >> struct cgroup_rstat_cpu *rstatc = cgroup_rstat_cpu(root, cpu); >> struct cgroup_subsys_state *head = NULL, *parent, *child; >> + raw_spinlock_t *cpu_lock; >> unsigned long flags; >> >> + if (is_base_css(root)) >> + cpu_lock = per_cpu_ptr(&cgroup_rstat_base_cpu_lock, cpu); >> + else >> + cpu_lock = per_cpu_ptr(cgroup_rstat_subsys_cpu_lock, cpu) + >> + root->ss->id; >> + >> flags = _cgroup_rstat_cpu_lock(cpu_lock, cpu, cgrp, false); >> >> /* Return NULL if this subtree is not on-list */ >> @@ -315,7 +336,7 @@ static void cgroup_rstat_flush_locked(struct cgroup_subsys_state *css, >> struct cgroup *cgrp = css->cgroup; >> int cpu; >> >> - lockdep_assert_held(&cgroup_rstat_lock); >> + lockdep_assert_held(&lock); >> >> for_each_possible_cpu(cpu) { >> struct cgroup_subsys_state *pos; >> @@ -356,12 +377,18 @@ static void cgroup_rstat_flush_locked(struct cgroup_subsys_state *css, >> __bpf_kfunc void cgroup_rstat_flush(struct cgroup_subsys_state *css) >> { >> struct cgroup *cgrp = css->cgroup; >> + spinlock_t *lock; >> + >> + if (is_base_css(css)) >> + lock = &cgroup_rstat_base_lock; >> + else >> + lock = &cgroup_rstat_subsys_lock[css->ss->id]; > > Same here. Also, instead of passing locks around, can we just pass > the css to __cgroup_rstat_lock/unlock() and have them find the correct > lock and use it directly? I like this and will take that approach in v3. It will allow the lock selection code you previously commented on to exist in just one place. > >> >> might_sleep(); >> >> - __cgroup_rstat_lock(&cgroup_rstat_lock, cgrp, -1); >> - cgroup_rstat_flush_locked(css, &cgroup_rstat_lock); >> - __cgroup_rstat_unlock(&cgroup_rstat_lock, cgrp, -1); >> + __cgroup_rstat_lock(lock, cgrp, -1); >> + cgroup_rstat_flush_locked(css, lock); >> + __cgroup_rstat_unlock(lock, cgrp, -1); >> } >> >> /** >> @@ -376,10 +403,16 @@ __bpf_kfunc void cgroup_rstat_flush(struct cgroup_subsys_state *css) >> void cgroup_rstat_flush_hold(struct cgroup_subsys_state *css) >> { >> struct cgroup *cgrp = css->cgroup; >> + spinlock_t *lock; >> + >> + if (is_base_css(css)) >> + lock = &cgroup_rstat_base_lock; >> + else >> + lock = &cgroup_rstat_subsys_lock[css->ss->id]; >> >> might_sleep(); >> - __cgroup_rstat_lock(&cgroup_rstat_lock, cgrp, -1); >> - cgroup_rstat_flush_locked(css, &cgroup_rstat_lock); >> + __cgroup_rstat_lock(lock, cgrp, -1); >> + cgroup_rstat_flush_locked(css, lock); >> } >> >> /** >> @@ -389,7 +422,14 @@ void cgroup_rstat_flush_hold(struct cgroup_subsys_state *css) >> void cgroup_rstat_flush_release(struct cgroup_subsys_state *css) >> { >> struct cgroup *cgrp = css->cgroup; >> - __cgroup_rstat_unlock(&cgroup_rstat_lock, cgrp, -1); >> + spinlock_t *lock; >> + >> + if (is_base_css(css)) >> + lock = &cgroup_rstat_base_lock; >> + else >> + lock = &cgroup_rstat_subsys_lock[css->ss->id]; >> + >> + __cgroup_rstat_unlock(lock, cgrp, -1); >> } >> >> int cgroup_rstat_init(struct cgroup_subsys_state *css) >> @@ -435,10 +475,21 @@ void cgroup_rstat_exit(struct cgroup_subsys_state *css) >> >> void __init cgroup_rstat_boot(void) >> { >> - int cpu; >> + struct cgroup_subsys *ss; >> + int cpu, ssid; >> >> - for_each_possible_cpu(cpu) >> - raw_spin_lock_init(per_cpu_ptr(&cgroup_rstat_cpu_lock, cpu)); >> + for_each_subsys(ss, ssid) { >> + spin_lock_init(&cgroup_rstat_subsys_lock[ssid]); >> + } >> + >> + for_each_possible_cpu(cpu) { >> + raw_spin_lock_init(per_cpu_ptr(&cgroup_rstat_base_cpu_lock, cpu)); >> + >> + for_each_subsys(ss, ssid) { >> + raw_spin_lock_init( >> + per_cpu_ptr(cgroup_rstat_subsys_cpu_lock, cpu) + ssid); >> + } >> + } >> } >> >> /* >> -- >> 2.43.5 >> >>