From: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
To: Pingfan Liu <kernelfans@gmail.com>, linux-mm@kvack.org
Cc: Andrew Morton <akpm@linux-foundation.org>,
Ira Weiny <ira.weiny@intel.com>,
Dan Williams <dan.j.williams@intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Mike Rapoport <rppt@linux.ibm.com>,
John Hubbard <jhubbard@nvidia.com>,
Keith Busch <keith.busch@intel.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm/gup: remove unnecessary check against CMA in __gup_longterm_locked()
Date: Tue, 4 Jun 2019 14:00:29 +0530 [thread overview]
Message-ID: <bb4fe1fe-dde0-b86b-740a-4b3dfa81d6f0@linux.ibm.com> (raw)
In-Reply-To: <1559633160-14809-1-git-send-email-kernelfans@gmail.com>
On 6/4/19 12:56 PM, Pingfan Liu wrote:
> The PF_MEMALLOC_NOCMA is set by memalloc_nocma_save(), which is finally
> cast to ~_GFP_MOVABLE. So __get_user_pages_locked() will get pages from
> non CMA area and pin them. There is no need to
> check_and_migrate_cma_pages().
That is not completely correct. We can fault in that pages outside
get_user_pages_longterm at which point those pages can get allocated
from CMA region. memalloc_nocma_save() as added as an optimization to
avoid unnecessary page migration.
-aneesh
next prev parent reply other threads:[~2019-06-04 8:30 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-04 7:26 Pingfan Liu
2019-06-04 8:30 ` Aneesh Kumar K.V [this message]
2019-06-04 8:50 ` Pingfan Liu
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