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Message-ID: <c66b2ce5-6f98-46be-bf0d-3172c17fa0f5@intel.com>
Date: Fri, 19 Apr 2024 22:03:20 +0800
User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH v1 05/18] mm: improve folio_likely_mapped_shared() using
 the mapcount of large folios
To: David Hildenbrand <david@redhat.com>, <linux-kernel@vger.kernel.org>
CC: <linux-mm@kvack.org>, <linux-doc@vger.kernel.org>,
	<cgroups@vger.kernel.org>, <linux-sh@vger.kernel.org>,
	<linux-trace-kernel@vger.kernel.org>, <linux-fsdevel@vger.kernel.org>,
	"Andrew Morton" <akpm@linux-foundation.org>, "Matthew Wilcox (Oracle)"
	<willy@infradead.org>, Peter Xu <peterx@redhat.com>, Ryan Roberts
	<ryan.roberts@arm.com>, Yang Shi <shy828301@gmail.com>, Zi Yan
	<ziy@nvidia.com>, Jonathan Corbet <corbet@lwn.net>, Hugh Dickins
	<hughd@google.com>, Yoshinori Sato <ysato@users.sourceforge.jp>, Rich Felker
	<dalias@libc.org>, John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>,
	Chris Zankel <chris@zankel.net>, Max Filippov <jcmvbkbc@gmail.com>, "Muchun
 Song" <muchun.song@linux.dev>, Miaohe Lin <linmiaohe@huawei.com>, "Naoya
 Horiguchi" <naoya.horiguchi@nec.com>, Richard Chang <richardycc@google.com>
References: <20240409192301.907377-1-david@redhat.com>
 <20240409192301.907377-6-david@redhat.com>
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From: "Yin, Fengwei" <fengwei.yin@intel.com>
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On 4/10/2024 3:22 AM, David Hildenbrand wrote:
> We can now read the mapcount of large folios very efficiently. Use it to
> improve our handling of partially-mappable folios, falling back
> to making a guess only in case the folio is not "obviously mapped shared".
> 
> We can now better detect partially-mappable folios where the first page is
> not mapped as "mapped shared", reducing "false negatives"; but false
> negatives are still possible.
> 
> While at it, fixup a wrong comment (false positive vs. false negative)
> for KSM folios.
> 
> Signed-off-by: David Hildenbrand <david@redhat.com>

Reviewed-by: Yin Fengwei <fengwei.yin@intel.com>