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From: Matthew Wilcox <willy@infradead.org>
To: Michal Hocko <mhocko@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Mike Kravetz <mike.kravetz@oracle.com>,
	Waiman Long <longman@redhat.com>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	aneesh.kumar@linux.ibm.com
Subject: Re: [PATCH v2] mm/hugetlb: defer free_huge_page() to a workqueue
Date: Mon, 16 Dec 2019 09:18:38 -0800	[thread overview]
Message-ID: <20191216171838.GA32169@bombadil.infradead.org> (raw)
In-Reply-To: <20191216161748.tgi2oictlfqy6azi@linux-p48b>

On Mon, Dec 16, 2019 at 08:17:48AM -0800, Davidlohr Bueso wrote:
> On Mon, 16 Dec 2019, Michal Hocko wrote:
> > I am afraid that work_struct is too large to be stuffed into the struct
> > page array (because of the lockdep part).
> 
> Yeah, this needs to be done without touching struct page.
> 
> Which is why I had done the stack allocated way in this patch, but we
> cannot wait for it to complete in irq, so that's out the window. Andi
> had suggested percpu allocated work items, but having played with the
> idea over the weekend, I don't see how we can prevent another page being
> freed on the same cpu before previous work on the same cpu is complete
> (cpu0 wants to free pageA, schedules the work, in the mean time cpu0
> wants to free pageB and workerfn for pageA still hasn't been called).

Why is it that we can call functions after-an-RCU-period-has-elapsed time,
at returning-to-userspace time and after-exiting-hardirq-handler
time easily, but the mechanism for calling a function
after-we've-finished-handling-softirqs is so bloody hard to use?

That's surely the major problem we need to fix.


  reply	other threads:[~2019-12-16 17:18 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-11 19:46 [PATCH v2] hugetlbfs: Disable softIRQ when taking hugetlb_lock Waiman Long
2019-12-11 22:04 ` Mike Kravetz
2019-12-11 22:19   ` Waiman Long
2019-12-12  1:11     ` Mike Kravetz
2019-12-12  6:06       ` Davidlohr Bueso
2019-12-12  6:30         ` Davidlohr Bueso
2019-12-12 19:04           ` [PATCH v2] mm/hugetlb: defer free_huge_page() to a workqueue Davidlohr Bueso
2019-12-12 19:22             ` Mike Kravetz
2019-12-12 19:36               ` Davidlohr Bueso
2019-12-12 20:52               ` Waiman Long
2019-12-12 21:04                 ` Waiman Long
2019-12-16 13:26                 ` Michal Hocko
2019-12-16 15:38                   ` Waiman Long
2019-12-16 18:44                     ` Waiman Long
2019-12-17  9:00                       ` Michal Hocko
2019-12-17 18:05                         ` Mike Kravetz
2019-12-18 12:18                           ` hugetlbfs testing coverage (was: Re: [PATCH v2] mm/hugetlb: defer free_huge_page() to a workqueue) Michal Hocko
2019-12-12 21:01             ` [PATCH v2] mm/hugetlb: defer free_huge_page() to a workqueue Waiman Long
2019-12-16 13:37             ` Michal Hocko
2019-12-16 16:17               ` Waiman Long
2019-12-16 16:17               ` Davidlohr Bueso
2019-12-16 17:18                 ` Matthew Wilcox [this message]
2019-12-16 19:08                 ` Mike Kravetz
2019-12-16 19:13                   ` Waiman Long
2019-12-12 21:32         ` [PATCH v2] hugetlbfs: Disable softIRQ when taking hugetlb_lock Andi Kleen
2019-12-12 22:42           ` Davidlohr Bueso
2019-12-11 23:05 ` Andi Kleen

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