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From: Matthew Wilcox <willy@infradead.org>
To: "Huang, Ying" <ying.huang@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	David Hildenbrand <david@redhat.com>,
	Mel Gorman <mgorman@suse.de>, Vlastimil Babka <vbabka@suse.cz>,
	Zi Yan <ziy@nvidia.com>, Michal Hocko <mhocko@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Minchan Kim <minchan@kernel.org>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Hugh Dickins <hughd@google.com>
Subject: Re: [RFC 0/3] mm: Discard lazily freed pages when migrating
Date: Thu, 27 Feb 2020 19:42:48 -0800	[thread overview]
Message-ID: <20200228034248.GE29971@bombadil.infradead.org> (raw)
In-Reply-To: <20200228033819.3857058-1-ying.huang@intel.com>

On Fri, Feb 28, 2020 at 11:38:16AM +0800, Huang, Ying wrote:
> MADV_FREE is a lazy free mechanism in Linux.  According to the manpage
> of mavise(2), the semantics of MADV_FREE is,
> 
>   The application no longer requires the pages in the range specified
>   by addr and len.  The kernel can thus free these pages, but the
>   freeing could be delayed until memory pressure occurs. ...
> 
> Originally, the pages freed lazily by MADV_FREE will only be freed
> really by page reclaiming when there is memory pressure or when
> unmapping the address range.  In addition to that, there's another
> opportunity to free these pages really, when we try to migrate them.
> 
> The main value to do that is to avoid to create the new memory
> pressure immediately if possible.  Instead, even if the pages are
> required again, they will be allocated gradually on demand.  That is,
> the memory will be allocated lazily when necessary.  This follows the
> common philosophy in the Linux kernel, allocate resources lazily on
> demand.

Do you have an example program which does this (and so benefits)?
If so, can you quantify the benefit at all?


  parent reply	other threads:[~2020-02-28  3:42 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-28  3:38 [RFC 0/3] mm: Discard lazily freed pages when migrating Huang, Ying
2020-02-28  3:38 ` [RFC 1/3] mm, migrate: Check return value of try_to_unmap() Huang, Ying
2020-02-28  3:38 ` [RFC 2/3] mm: Add a new page flag PageLayzyFree() for MADV_FREE Huang, Ying
2020-02-28  6:13   ` David Hildenbrand
2020-02-28  6:47     ` Huang, Ying
2020-03-15  8:18   ` Wei Yang
2020-03-15  8:54     ` Mika Penttilä
2020-03-15 12:22       ` Wei Yang
2020-03-16  1:21         ` Huang, Ying
2020-03-16 22:38           ` Wei Yang
2020-02-28  3:38 ` [RFC 3/3] mm: Discard lazily freed pages when migrating Huang, Ying
2020-02-28  3:42 ` Matthew Wilcox [this message]
2020-02-28  7:25   ` [RFC 0/3] " Huang, Ying
2020-02-28  8:22     ` David Hildenbrand
2020-02-28  8:55       ` Huang, Ying
2020-02-28  9:49         ` Mel Gorman
2020-03-02 11:23           ` Huang, Ying
2020-03-02 15:16             ` Mel Gorman
2020-03-03  1:51               ` Huang, Ying
2020-03-03  8:09                 ` Michal Hocko
2020-03-03  8:47                   ` Huang, Ying
2020-03-03  8:58                     ` Michal Hocko
2020-03-03 11:49                       ` Huang, Ying
2020-03-04  9:58                         ` Michal Hocko
2020-03-04 10:56                           ` Mel Gorman
2020-03-05  1:42                             ` Huang, Ying
2020-03-04 11:15                           ` Huang, Ying
2020-03-04 11:26                             ` Michal Hocko
2020-03-05  1:45                               ` Huang, Ying
2020-03-05 10:48                             ` Mel Gorman
2020-03-06  4:05                               ` Huang, Ying
2020-03-09  5:26                               ` Huang, Ying
2020-03-03 13:02                 ` Mel Gorman
2020-03-04  0:33                   ` Huang, Ying
2020-02-28  9:50         ` Michal Hocko
2020-02-28 10:15           ` Michal Hocko
2020-02-28 13:45           ` Johannes Weiner
2020-03-02 14:12           ` Huang, Ying
2020-03-02 14:23             ` David Hildenbrand
2020-03-03  0:25               ` Huang, Ying
2020-03-02 14:25             ` Michal Hocko
2020-03-03  1:30               ` Huang, Ying
2020-03-03  8:19                 ` Michal Hocko
2020-03-03 11:36                   ` Huang, Ying

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