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[2607:7c80:54:e::133]) by mx.google.com with ESMTPS id p6si5353319pgi.531.2019.03.21.15.00.45 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 21 Mar 2019 15:00:45 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of peterz@infradead.org designates 2607:7c80:54:e::133 as permitted sender) client-ip=2607:7c80:54:e::133; Authentication-Results: mx.google.com; dkim=pass header.i=@infradead.org header.s=bombadil.20170209 header.b=pSWHajQs; spf=pass (google.com: best guess record for domain of peterz@infradead.org designates 2607:7c80:54:e::133 as permitted sender) smtp.mailfrom=peterz@infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=JVdztBDJcSey0QI9UZ8uSOMuJf9GvmkjJ47WwH+ajqs=; b=pSWHajQsPC7Dnpe2r+iQ7C2or UFxfv/su+iL/pKAP1gL41nDsBFsAb+DZM7b3AC8jaWN1Nbr6zTLE4rlY7vXWA6ShCSc+lKp24ZqUG qhRw/NfaVJZq1G/CZ36bCkP/M+xVdDArAkWcgTFPjD32YIh0KrgZKLFiUJQHkaz2C83VSRMMOm2GV D2jvftVr170zAbhGkv4lfpzXvHNnGDd0q40AKVeo7vgk2svIcocNRSlzTKx1GjXiti2EhTXA7ASG4 6fLbS8rQB6J+iUyMkw9PqSK7xGSs6ue2cucX/lcfS8l9qu+ffGrvUpFoYiWLToHMAzHZhgA5KgGNU 6C1Eh4s7w==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=worktop.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1h75jr-0001Fe-Im; Thu, 21 Mar 2019 22:00:40 +0000 Received: by worktop.programming.kicks-ass.net (Postfix, from userid 1000) id 737E7984EEA; Thu, 21 Mar 2019 23:00:35 +0100 (CET) Date: Thu, 21 Mar 2019 23:00:35 +0100 From: Peter Zijlstra To: Waiman Long Cc: Andrew Morton , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , linux-kernel@vger.kernel.org, linux-mm@kvack.org, selinux@vger.kernel.org, Paul Moore , Stephen Smalley , Eric Paris , Oleg Nesterov Subject: Re: [PATCH 4/4] mm: Do periodic rescheduling when freeing objects in kmem_free_up_q() Message-ID: <20190321220035.GF7905@worktop.programming.kicks-ass.net> References: <20190321214512.11524-1-longman@redhat.com> <20190321214512.11524-5-longman@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190321214512.11524-5-longman@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) 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: On Thu, Mar 21, 2019 at 05:45:12PM -0400, Waiman Long wrote: > If the freeing queue has many objects, freeing all of them consecutively > may cause soft lockup especially on a debug kernel. So kmem_free_up_q() > is modified to call cond_resched() if running in the process context. > > Signed-off-by: Waiman Long > --- > mm/slab_common.c | 11 ++++++++++- > 1 file changed, 10 insertions(+), 1 deletion(-) > > diff --git a/mm/slab_common.c b/mm/slab_common.c > index dba20b4208f1..633a1d0f6d20 100644 > --- a/mm/slab_common.c > +++ b/mm/slab_common.c > @@ -1622,11 +1622,14 @@ EXPORT_SYMBOL_GPL(kmem_free_q_add); > * kmem_free_up_q - free all the objects in the freeing queue > * @head: freeing queue head > * > - * Free all the objects in the freeing queue. > + * Free all the objects in the freeing queue. The caller cannot hold any > + * non-sleeping locks. > */ > void kmem_free_up_q(struct kmem_free_q_head *head) > { > struct kmem_free_q_node *node, *next; > + bool do_resched = !in_irq(); > + int cnt = 0; > > for (node = head->first; node; node = next) { > next = node->next; > @@ -1634,6 +1637,12 @@ void kmem_free_up_q(struct kmem_free_q_head *head) > kmem_cache_free(node->cachep, node); > else > kfree(node); > + /* > + * Call cond_resched() every 256 objects freed when in > + * process context. > + */ > + if (do_resched && !(++cnt & 0xff)) > + cond_resched(); Why not just: cond_resched() ? > } > } > EXPORT_SYMBOL_GPL(kmem_free_up_q); > -- > 2.18.1 >