From: Matthew Wilcox <willy@infradead.org>
To: Mina Almasry <almasrymina@google.com>
Cc: no@kvack.org, To-header@kvack.org, on@kvack.org,
"input <"@kvack.org;, "Paul E . McKenney" <paulmckrcu@fb.com>,
Yu Zhao <yuzhao@google.com>, Jonathan Corbet <corbet@lwn.net>,
Andrew Morton <akpm@linux-foundation.org>,
Peter Xu <peterx@redhat.com>,
Ivan Teterevkov <ivan.teterevkov@nutanix.com>,
David Hildenbrand <david@redhat.com>,
Florian Schmidt <florian.schmidt@nutanix.com>,
linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org
Subject: Re: [PATCH v2] mm: Add PM_THP to /proc/pid/pagemap
Date: Thu, 4 Nov 2021 22:05:41 +0000 [thread overview]
Message-ID: <YYRZNWZqHy9+11KW@casper.infradead.org> (raw)
In-Reply-To: <20211104214636.450782-1-almasrymina@google.com>
On Thu, Nov 04, 2021 at 02:46:35PM -0700, Mina Almasry wrote:
> Add PM_THP to allow userspace to detect whether a given virt address is
> currently mapped by a hugepage or not.
Well, no, that's not what that means.
> @@ -1396,6 +1397,8 @@ static pagemap_entry_t pte_to_pagemap_entry(struct pagemapread *pm,
> flags |= PM_FILE;
> if (page && page_mapcount(page) == 1)
> flags |= PM_MMAP_EXCLUSIVE;
> + if (page && PageTransCompound(page))
> + flags |= PM_THP;
All that PageTransCompound() does is call PageCompound(). It doesn't
tell you if the underlying allocation is PMD sized, nor properly aligned.
And you didn't answer my question about whether you want information about
whether a large page is being used that's not quite as large as a PMD.
next prev parent reply other threads:[~2021-11-04 22:10 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-04 21:46 Mina Almasry
2021-11-04 22:05 ` Matthew Wilcox [this message]
2021-11-04 22:45 ` Mina Almasry
2021-11-07 22:56 ` Mina Almasry
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