From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AIpwx49wXPamkJAN6HXbT5mjPY+l41o9j4C3quy0wNekVUuQmCtbyWtQt5CtyNCzl4whtQ2SVyAl ARC-Seal: i=1; a=rsa-sha256; t=1524406319; cv=none; d=google.com; s=arc-20160816; b=T2P0mYdStlfmJ6ZX+2FJ9CMaIWl7t15SG8q1Ma5+jEfylJGhjj1I2YnQKfIxKFxJsm 6Zyltl5RzlKYZdmLmtSWVK2r4idsKrTkF6CxptxhMCzJo/2J7Sj0+kk+/Bpu11zjvtJb oLSAuoZjwNFQDwoy0Eam0bMbt99rxSXWA0zKh5nIKU2djm9nRWRLcHJrcKkS23ghstiS eNkH92zz6v0AI85equg9rprMLHe+kJQpjbHcUhvw8fdsIumplIFM+Le5vTI5AkDLocL+ 5QE/rGPsLD/2hEEfuAYez2/YxMjdENd30hkZbtzciRwaZwPpWgYNRUydpZ9UvHTvJzy/ gFcQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=mime-version:user-agent:references:in-reply-to:message-id:date :subject:cc:to:from:arc-authentication-results; bh=tL99ktpevfSKsRENxmmxoR3NRrM6PMAIyfwYW36/nxQ=; b=miNcPmd5yVuHLf/ZU/RWf7S4ukU9xQNwpPb666GBnkhDMGcvIltBw7isZGn4cwSKjq Ra21tzGsgkCBPHrvoAx9/Q5KZIqvOCsxixlzD47ynKmUD4Q146M2XgH180apDmCtouYj eI+hdbxx6PYX9gbIg8vbVnUcxTdmc1Xws8iK3w+mOneKJaiHmC46pYCWw2nGF3S0bvdH 2D7eOePxyO3DX7oUK3tdXnYUJGQ7xRKuerDoggsNccKBw+v53TuJg6tokqgJfHKeDas1 SFiCgakcDg6tEaQm318WdOnCQUhJf/cpPMMTWZWloj8SWbdf4l8o+8nW7kAuP40xaoZn XHfA== ARC-Authentication-Results: i=1; mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 90.92.61.202 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 90.92.61.202 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Vlastimil Babka , Pekka Enberg , Christoph Lameter , Joonsoo Kim , David Rientjes , Tejun Heo , Lai Jiangshan , John Stultz , Thomas Gleixner , Stephen Boyd , Andrew Morton , Linus Torvalds Subject: [PATCH 4.9 09/95] mm, slab: reschedule cache_reap() on the same CPU Date: Sun, 22 Apr 2018 15:52:38 +0200 Message-Id: <20180422135210.807931140@linuxfoundation.org> X-Mailer: git-send-email 2.17.0 In-Reply-To: <20180422135210.432103639@linuxfoundation.org> References: <20180422135210.432103639@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-LABELS: =?utf-8?b?IlxcU2VudCI=?= X-GMAIL-THRID: =?utf-8?q?1598454810628611405?= X-GMAIL-MSGID: =?utf-8?q?1598455880591026859?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Vlastimil Babka commit a9f2a846f0503e7d729f552e3ccfe2279010fe94 upstream. cache_reap() is initially scheduled in start_cpu_timer() via schedule_delayed_work_on(). But then the next iterations are scheduled via schedule_delayed_work(), i.e. using WORK_CPU_UNBOUND. Thus since commit ef557180447f ("workqueue: schedule WORK_CPU_UNBOUND work on wq_unbound_cpumask CPUs") there is no guarantee the future iterations will run on the originally intended cpu, although it's still preferred. I was able to demonstrate this with /sys/module/workqueue/parameters/debug_force_rr_cpu. IIUC, it may also happen due to migrating timers in nohz context. As a result, some cpu's would be calling cache_reap() more frequently and others never. This patch uses schedule_delayed_work_on() with the current cpu when scheduling the next iteration. Link: http://lkml.kernel.org/r/20180411070007.32225-1-vbabka@suse.cz Fixes: ef557180447f ("workqueue: schedule WORK_CPU_UNBOUND work on wq_unbound_cpumask CPUs") Signed-off-by: Vlastimil Babka Acked-by: Pekka Enberg Acked-by: Christoph Lameter Cc: Joonsoo Kim Cc: David Rientjes Cc: Tejun Heo Cc: Lai Jiangshan Cc: John Stultz Cc: Thomas Gleixner Cc: Stephen Boyd Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/slab.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/mm/slab.c +++ b/mm/slab.c @@ -4096,7 +4096,8 @@ next: next_reap_node(); out: /* Set up the next iteration */ - schedule_delayed_work(work, round_jiffies_relative(REAPTIMEOUT_AC)); + schedule_delayed_work_on(smp_processor_id(), work, + round_jiffies_relative(REAPTIMEOUT_AC)); } #ifdef CONFIG_SLABINFO