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Wed, 21 Apr 2021 03:52:05 -0700 (PDT) Date: Wed, 21 Apr 2021 12:51:31 +0200 In-Reply-To: <20210421105132.3965998-1-elver@google.com> Message-Id: <20210421105132.3965998-3-elver@google.com> Mime-Version: 1.0 References: <20210421105132.3965998-1-elver@google.com> X-Mailer: git-send-email 2.31.1.368.gbe11c130af-goog Subject: [PATCH v2 2/3] kfence: maximize allocation wait timeout duration From: Marco Elver To: elver@google.com, akpm@linux-foundation.org Cc: glider@google.com, dvyukov@google.com, jannh@google.com, mark.rutland@arm.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, kasan-dev@googlegroups.com, hdanton@sina.com X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 9427740002E1 X-Stat-Signature: hrweeb34jgetuhu39w4rsangsgn84wik Received-SPF: none (flex--elver.bounces.google.com>: No applicable sender policy available) receiver=imf17; identity=mailfrom; envelope-from="<31QOAYAUKCOYMTdMZOWWOTM.KWUTQVcf-UUSdIKS.WZO@flex--elver.bounces.google.com>"; helo=mail-ej1-f74.google.com; client-ip=209.85.218.74 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1619002323-194433 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: The allocation wait timeout was initially added because of warnings due to CONFIG_DETECT_HUNG_TASK=y [1]. While the 1 sec timeout is sufficient to resolve the warnings (given the hung task timeout must be 1 sec or larger) it may cause unnecessary wake-ups if the system is idle. [1] https://lkml.kernel.org/r/CADYN=9J0DQhizAGB0-jz4HOBBh+05kMBXb4c0cXMS7Qi5NAJiw@mail.gmail.com Fix it by computing the timeout duration in terms of the current sysctl_hung_task_timeout_secs value. Signed-off-by: Marco Elver --- mm/kfence/core.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/mm/kfence/core.c b/mm/kfence/core.c index 235d726f88bc..9742649f3f88 100644 --- a/mm/kfence/core.c +++ b/mm/kfence/core.c @@ -20,6 +20,7 @@ #include #include #include +#include #include #include #include @@ -621,7 +622,16 @@ static void toggle_allocation_gate(struct work_struct *work) /* Enable static key, and await allocation to happen. */ static_branch_enable(&kfence_allocation_key); - wait_event_timeout(allocation_wait, atomic_read(&kfence_allocation_gate), HZ); + if (sysctl_hung_task_timeout_secs) { + /* + * During low activity with no allocations we might wait a + * while; let's avoid the hung task warning. + */ + wait_event_timeout(allocation_wait, atomic_read(&kfence_allocation_gate), + sysctl_hung_task_timeout_secs * HZ / 2); + } else { + wait_event(allocation_wait, atomic_read(&kfence_allocation_gate)); + } /* Disable static key and reset timer. */ static_branch_disable(&kfence_allocation_key);