From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Michal Hocko <mhocko@kernel.org>,
Mel Gorman <mgorman@techsingularity.net>,
Matthew Wilcox <willy@infradead.org>
Subject: Re: [PATCH 1/3] mm, page_owner: record page owner for each subpage
Date: Fri, 16 Aug 2019 17:04:30 +0300 [thread overview]
Message-ID: <20190816140430.aoya6k7qxxrls72h@box> (raw)
In-Reply-To: <20190816101401.32382-2-vbabka@suse.cz>
On Fri, Aug 16, 2019 at 12:13:59PM +0200, Vlastimil Babka wrote:
> Currently, page owner info is only recorded for the first page of a high-order
> allocation, and copied to tail pages in the event of a split page. With the
> plan to keep previous owner info after freeing the page, it would be benefical
> to record page owner for each subpage upon allocation. This increases the
> overhead for high orders, but that should be acceptable for a debugging option.
>
> The order stored for each subpage is the order of the whole allocation. This
> makes it possible to calculate the "head" pfn and to recognize "tail" pages
> (quoted because not all high-order allocations are compound pages with true
> head and tail pages). When reading the page_owner debugfs file, keep skipping
> the "tail" pages so that stats gathered by existing scripts don't get inflated.
>
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Hm. That's all reasonable, but I have a question: do you see how page
owner thing works for THP now?
I don't see anything in split_huge_page() path (do not confuse it with
split_page() path) that would copy the information to tail pages. Do you?
--
Kirill A. Shutemov
next prev parent reply other threads:[~2019-08-16 14:04 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-16 10:13 [PATCH 0/3] debug_pagealloc improvements through page_owner Vlastimil Babka
2019-08-16 10:13 ` [PATCH 1/3] mm, page_owner: record page owner for each subpage Vlastimil Babka
2019-08-16 14:04 ` Kirill A. Shutemov [this message]
2019-08-19 11:46 ` Vlastimil Babka
2019-08-19 11:55 ` Kirill A. Shutemov
2019-08-19 11:57 ` Kirill A. Shutemov
2019-08-19 13:11 ` Vlastimil Babka
2019-08-16 10:14 ` [PATCH 2/3] mm, page_owner: keep owner info when freeing the page Vlastimil Babka
2019-08-16 10:14 ` [PATCH 3/3] mm, page_owner, debug_pagealloc: save and dump freeing stack trace Vlastimil Babka
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