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From: Peter Zijlstra <peterz@infradead.org>
To: Mike Kravetz <mike.kravetz@oracle.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	Michal Hocko <mhocko@suse.com>,
	Shakeel Butt <shakeelb@google.com>,
	Oscar Salvador <osalvador@suse.de>,
	David Hildenbrand <david@redhat.com>,
	Muchun Song <songmuchun@bytedance.com>,
	David Rientjes <rientjes@google.com>,
	Miaohe Lin <linmiaohe@huawei.com>,
	Matthew Wilcox <willy@infradead.org>,
	HORIGUCHI NAOYA <naoya.horiguchi@nec.com>,
	"Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>,
	Waiman Long <longman@redhat.com>, Peter Xu <peterx@redhat.com>,
	Mina Almasry <almasrymina@google.com>,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [RFC PATCH 7/8] hugetlb: add update_and_free_page_no_sleep for irq context
Date: Mon, 22 Mar 2021 09:41:01 +0100	[thread overview]
Message-ID: <YFhYHZ9onwdZMeDi@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20210319224209.150047-8-mike.kravetz@oracle.com>

On Fri, Mar 19, 2021 at 03:42:08PM -0700, Mike Kravetz wrote:
> The locks acquired in free_huge_page are irq safe.  However, in certain
> circumstances the routine update_and_free_page could sleep.  Since
> free_huge_page can be called from any context, it can not sleep.
> 
> Use a waitqueue to defer freeing of pages if the operation may sleep.  A
> new routine update_and_free_page_no_sleep provides this functionality
> and is only called from free_huge_page.
> 
> Note that any 'pages' sent to the workqueue for deferred freeing have
> already been removed from the hugetlb subsystem.  What is actually
> deferred is returning those base pages to the low level allocator.

So maybe I'm stupid, but why do you need that work in hugetlb? Afaict it
should be in cma_release().

Also, afaict cma_release() does free_contig_range() *first*, and then
does the 'difficult' bits. So how about you re-order
free_gigantic_page() a bit to make it unconditionally do
free_contig_range() and *then* call into CMA, which can then do a
workqueue thingy if it feels like it.

That way none of the hugetlb accounting is delayed, and only CMA gets to
suffer.

  parent reply	other threads:[~2021-03-22  8:42 UTC|newest]

Thread overview: 47+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-19 22:42 [RFC PATCH 0/8] make hugetlb put_page safe for all calling contexts Mike Kravetz
2021-03-19 22:42 ` [RFC PATCH 1/8] hugetlb: add per-hstate mutex to synchronize user adjustments Mike Kravetz
2021-03-22 13:59   ` Michal Hocko
2021-03-22 16:57     ` Mike Kravetz
2021-03-23  7:48       ` Michal Hocko
2021-03-19 22:42 ` [RFC PATCH 2/8] hugetlb: recompute min_count when dropping hugetlb_lock Mike Kravetz
2021-03-22 14:07   ` Michal Hocko
2021-03-22 23:07     ` Mike Kravetz
2021-03-23  7:50       ` Michal Hocko
2021-03-23  8:01         ` Peter Zijlstra
2021-03-23  8:14           ` Michal Hocko
2021-03-23 23:18             ` Mike Kravetz
2021-03-24  8:36               ` Michal Hocko
2021-03-24 16:43                 ` Mike Kravetz
2021-03-19 22:42 ` [RFC PATCH 3/8] hugetlb: create remove_hugetlb_page() to separate functionality Mike Kravetz
2021-03-22 14:15   ` Michal Hocko
2021-03-22 17:01     ` Mike Kravetz
2021-03-19 22:42 ` [RFC PATCH 4/8] hugetlb: call update_and_free_page without hugetlb_lock Mike Kravetz
2021-03-22 14:19   ` Michal Hocko
2021-03-19 22:42 ` [RFC PATCH 5/8] hugetlb: change free_pool_huge_page to remove_pool_huge_page Mike Kravetz
2021-03-22 14:31   ` Michal Hocko
2021-03-22 23:28     ` Mike Kravetz
2021-03-23  7:57       ` Michal Hocko
2021-03-24  1:03         ` Mike Kravetz
2021-03-24  8:40           ` Michal Hocko
2021-03-24 16:38             ` Mike Kravetz
2021-03-24 16:50               ` Michal Hocko
2021-03-19 22:42 ` [RFC PATCH 6/8] hugetlb: make free_huge_page irq safe Mike Kravetz
2021-03-21 19:55   ` Mike Kravetz
2021-03-22 13:36   ` [hugetlb] cd190f60f9: BUG:sleeping_function_called_from_invalid_context_at_mm/hugetlb.c kernel test robot
2021-03-22 13:36     ` kernel test robot
2021-03-22 13:36     ` [LTP] " kernel test robot
2021-03-22 14:35   ` [RFC PATCH 6/8] hugetlb: make free_huge_page irq safe Michal Hocko
2021-03-19 22:42 ` [RFC PATCH 7/8] hugetlb: add update_and_free_page_no_sleep for irq context Mike Kravetz
2021-03-20  1:18   ` Hillf Danton
2021-03-25  0:26     ` Mike Kravetz
2021-03-22  8:41   ` Peter Zijlstra [this message]
2021-03-22 17:42     ` Mike Kravetz
2021-03-22 18:10       ` Roman Gushchin
2021-03-23 18:51         ` Mike Kravetz
2021-03-23 19:07           ` Roman Gushchin
2021-03-24  8:43           ` Michal Hocko
2021-03-24 16:53             ` Mike Kravetz
2021-03-22 20:43       ` Peter Zijlstra
2021-03-22 14:42   ` Michal Hocko
2021-03-22 14:46     ` Michal Hocko
2021-03-19 22:42 ` [RFC PATCH 8/8] hugetlb: track hugetlb pages allocated via cma_alloc Mike Kravetz

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