From: Michal Hocko <mhocko@suse.com>
To: Muchun Song <songmuchun@bytedance.com>
Cc: Oscar Salvador <osalvador@suse.de>,
Mike Kravetz <mike.kravetz@oracle.com>,
Andrew Morton <akpm@linux-foundation.org>,
Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
Andi Kleen <ak@linux.intel.com>,
Linux Memory Management List <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [External] Re: [PATCH v4 4/6] mm: hugetlb: retry dissolve page when hitting race
Date: Wed, 13 Jan 2021 13:03:20 +0100 [thread overview]
Message-ID: <20210113120320.GY22493@dhcp22.suse.cz> (raw)
In-Reply-To: <CAMZfGtWn95u2s11MUk33z4MDVec5j4+usRasTqHxRp9Ud73mSA@mail.gmail.com>
On Wed 13-01-21 19:20:17, Muchun Song wrote:
> On Wed, Jan 13, 2021 at 7:15 PM Oscar Salvador <osalvador@suse.de> wrote:
> >
> > On Wed, Jan 13, 2021 at 07:11:06PM +0800, Muchun Song wrote:
> > > If there is no task to be scheduled. Here is just a while loop.
> > > The cpu_relax is a good thing to insert into busy-wait loops,
> > > right?
> >
> > But if the race window is that small, does it make sense?
>
> Actually, there is one exception. The race window could
> become larger. If the page is freed via a workqueue (see
> free_huge_page()). In this case, the cpu_relax() can
> make sense. Right?
The system would have to be under serious stress for WQ to clog. I do
not expect there would be nothing runable at that stage. Possible?
Maybe but if that matters than a short sleep would be more preferable
than cpu_relax.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2021-01-13 12:04 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-13 5:22 [PATCH v4 0/6] Fix some bugs about HugeTLB code Muchun Song
2021-01-13 5:22 ` [PATCH v4 1/6] mm: migrate: do not migrate HugeTLB page whose refcount is one Muchun Song
2021-01-13 10:30 ` David Hildenbrand
2021-01-13 10:57 ` Oscar Salvador
2021-01-13 11:03 ` [External] " Muchun Song
2021-01-13 11:03 ` Muchun Song
2021-01-13 5:22 ` [PATCH v4 2/6] mm: hugetlbfs: fix cannot migrate the fallocated HugeTLB page Muchun Song
2021-01-13 11:00 ` Oscar Salvador
2021-01-13 5:22 ` [PATCH v4 3/6] mm: hugetlb: fix a race between freeing and dissolving the page Muchun Song
2021-01-13 9:31 ` Michal Hocko
2021-01-13 5:22 ` [PATCH v4 4/6] mm: hugetlb: retry dissolve page when hitting race Muchun Song
2021-01-13 9:33 ` Michal Hocko
2021-01-13 10:14 ` [External] " Muchun Song
2021-01-13 10:14 ` Muchun Song
2021-01-13 10:38 ` Michal Hocko
2021-01-13 11:11 ` Muchun Song
2021-01-13 11:11 ` Muchun Song
2021-01-13 11:14 ` Oscar Salvador
2021-01-13 11:20 ` Muchun Song
2021-01-13 11:20 ` Muchun Song
2021-01-13 12:03 ` Michal Hocko [this message]
2021-01-13 11:22 ` Michal Hocko
2021-01-13 12:15 ` Muchun Song
2021-01-13 12:15 ` Muchun Song
2021-01-13 5:22 ` [PATCH v4 5/6] mm: hugetlb: fix a race between isolating and freeing page Muchun Song
2021-01-13 5:22 ` [PATCH v4 6/6] mm: hugetlb: remove VM_BUG_ON_PAGE from page_huge_active Muchun Song
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