linux-kernel - Re: [PATCH v9 07/10] mm: Device exclusive memory access

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Message-ID: <10231977.pWpf7cJbZl@nvdebian>
Date:   Fri, 4 Jun 2021 11:07:42 +1000
From:   Alistair Popple <apopple@...dia.com>
To:     Peter Xu <peterx@...hat.com>
CC:     Balbir Singh <bsingharora@...il.com>,
        John Hubbard <jhubbard@...dia.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        <linux-mm@...ck.org>, <nouveau@...ts.freedesktop.org>,
        <bskeggs@...hat.com>, <rcampbell@...dia.com>,
        <linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <dri-devel@...ts.freedesktop.org>, <hch@...radead.org>,
        <jglisse@...hat.com>, <willy@...radead.org>, <jgg@...dia.com>,
        <hughd@...gle.com>, Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v9 07/10] mm: Device exclusive memory access

On Friday, 4 June 2021 12:47:40 AM AEST Peter Xu wrote:
> External email: Use caution opening links or attachments
> 
> On Thu, Jun 03, 2021 at 09:39:32PM +1000, Alistair Popple wrote:
> > Reclaim won't run on the page due to the extra references from the special
> > swap entries.
> 
> That sounds reasonable, but I didn't find the point that stops it, probably
> due to my limited knowledge on the reclaim code.  Could you elaborate?

Sure, it isn't immediately obvious but it ends up being detected at the start 
of is_page_cache_freeable() in the pageout code:


static pageout_t pageout(struct page *page, struct address_space *mapping)
{

[...]

	if (!is_page_cache_freeable(page))
		return PAGE_KEEP;

 - Alistair

> --
> Peter Xu