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Shutemov" , Michal Hocko , Mike Kravetz , Shuah Khan , Vlastimil Babka , Matthew Wilcox , , , , , , LKML , John Hubbard , "Kirill A . Shutemov" Subject: [PATCH v5 09/12] mm: dump_page(): better diagnostics for huge pinned pages Date: Thu, 6 Feb 2020 19:37:32 -0800 Message-ID: <20200207033735.308000-10-jhubbard@nvidia.com> X-Mailer: git-send-email 2.25.0 In-Reply-To: <20200207033735.308000-1-jhubbard@nvidia.com> References: <20200207033735.308000-1-jhubbard@nvidia.com> MIME-Version: 1.0 X-NVConfidentiality: public Content-Transfer-Encoding: quoted-printable Content-Type: text/plain DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1581046599; bh=jmOUjzJ549EfFTXaNo+IqA1m0L9Edt0hTMtlZOuZ9oI=; h=X-PGP-Universal:From:To:CC:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:X-NVConfidentiality: Content-Transfer-Encoding:Content-Type; b=ef/4udRoouVf31SNt8dxH8rGemdY2KQ3FUhL1foXTZbDgzP4IyhLK4YjOkoH8c4J7 vZIBhMUtt/Q4ked+2xEBrgqdgHxMVPEsMO+ZlJHNnQBUA0b/dN7rEQuPkTfxV5Iz+m YwMe+ClfugPn1gCR754PWzgyqnw3AwyYFOcqRCqkmf5o2pBbdcO5A8xjcfl4on2s17 zxAj6h1KNcrH4VfNdeKRUNav6fFaca+k9pEYjlc5vne5iyY9kswBj9/R7pYLkzXyQ4 Vp5jnRVUcRp0yCDbFslLV8IXO7B+toifjZo7qM2L5LOadtrhiHvkBEE9Lq9NvmG1A3 7txFYKNBc41Kg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: As part of pin_user_pages() and related API calls, pages are "dma-pinned". For the case of compound pages of order > 1, the per-page accounting of dma pins is accomplished via the 3rd struct page in the compound page. In order to support debugging of any pin_user_pages()- related problems, enhance dump_page() so as to report the pin count in that case. Documentation/core-api/pin_user_pages.rst is also updated accordingly. Acked-by: Kirill A. Shutemov Reviewed-by: Jan Kara Signed-off-by: John Hubbard --- Documentation/core-api/pin_user_pages.rst | 7 +++++ mm/debug.c | 34 +++++++++++++++++------ 2 files changed, 33 insertions(+), 8 deletions(-) diff --git a/Documentation/core-api/pin_user_pages.rst b/Documentation/core= -api/pin_user_pages.rst index 7e5dd8b1b3f2..24641f1a1eba 100644 --- a/Documentation/core-api/pin_user_pages.rst +++ b/Documentation/core-api/pin_user_pages.rst @@ -215,6 +215,13 @@ Those are both going to show zero, unless CONFIG_DEBUG= _VM is set. This is because there is a noticeable performance drop in unpin_user_page(), when = they are activated. =20 +Other diagnostics +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D + +dump_page() has been enhanced slightly, to handle these new counting field= s, and +to better report on compound pages in general. Specifically, for compound = pages +with order > 1, the exact (hpage_pinned_refcount) pincount is reported. + References =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =20 diff --git a/mm/debug.c b/mm/debug.c index f074077eee11..e82c878c27df 100644 --- a/mm/debug.c +++ b/mm/debug.c @@ -57,10 +57,20 @@ static void __dump_tail_page(struct page *page, int map= count) page, page_ref_count(page), mapcount, page->mapping, page_to_pgoff(page)); } else { - pr_warn("page:%px compound refcount:%d mapcount:%d mapping:%px " - "index:%#lx compound_mapcount:%d\n", - page, page_ref_count(head), mapcount, head->mapping, - page_to_pgoff(head), compound_mapcount(page)); + if (hpage_pincount_available(page)) + pr_warn("page:%px compound refcount:%d mapcount:%d " + "mapping:%px index:%#lx compound_mapcount:%d " + "compound_pincount:%d\n", + page, page_ref_count(head), mapcount, + head->mapping, page_to_pgoff(head), + compound_mapcount(page), + compound_pincount(page)); + else + pr_warn("page:%px compound refcount:%d mapcount:%d " + "mapping:%px index:%#lx compound_mapcount:%d\n", + page, page_ref_count(head), mapcount, + head->mapping, page_to_pgoff(head), + compound_mapcount(page)); } =20 if (page_ref_count(page) !=3D 0) { @@ -104,10 +114,18 @@ void __dump_page(struct page *page, const char *reaso= n) =20 if (PageTail(page)) __dump_tail_page(page, mapcount); - else - pr_warn("page:%px refcount:%d mapcount:%d mapping:%px index:%#lx\n", - page, page_ref_count(page), mapcount, - page->mapping, page_to_pgoff(page)); + else { + if (hpage_pincount_available(page)) + pr_warn("page:%px refcount:%d mapcount:%d mapping:%px " + "index:%#lx compound pincount: %d\n", + page, page_ref_count(page), mapcount, + page->mapping, page_to_pgoff(page), + compound_pincount(page)); + else + pr_warn("page:%px refcount:%d mapcount:%d mapping:%px " + "index:%#lx\n", page, page_ref_count(page), + mapcount, page->mapping, page_to_pgoff(page)); + } if (PageKsm(page)) type =3D "ksm "; else if (PageAnon(page)) --=20 2.25.0