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Shutemov" , Michal Hocko , Mike Kravetz , Shuah Khan , Vlastimil Babka , , , , , , LKML , John Hubbard Subject: [PATCH v2 6/8] mm/gup: /proc/vmstat: pin_user_pages (FOLL_PIN) reporting Date: Tue, 28 Jan 2020 19:24:15 -0800 Message-ID: <20200129032417.3085670-7-jhubbard@nvidia.com> X-Mailer: git-send-email 2.25.0 In-Reply-To: <20200129032417.3085670-1-jhubbard@nvidia.com> References: <20200129032417.3085670-1-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=1580268209; bh=BR5qP9yDgHwmms8MxoALGGT7QIGUZw1rw8GRkZlTQFY=; 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=nFQ9T3Plvdjga7ESszH/TTmMo2dq9KemHTy4oyIwG8+mvuav1sSzZUU/CsVXO4uqG xkK+Vv/udS+xWFaIRVTPRPOgGf9tkLA4daR3jYi+DP2gmM4KMSAbCCoxgtWaRj8SH3 18WhbdSSVXcEK3zKvhuJ7r7VmmtKXQiwxhH9DLVtq6gWvoywUyWMAZL0+YqPc1aFvS P/5XuBVdYY+mtxW1M76o3X94bBDVHmHDP/UDbppjRR3Zhgt/271ttfPSByDWBzvTTb HpM82D+sICghg9fJ7ITMwpRDyJYrjdts4MLkUgkFYxUFDTKGSeEXW55Efux6DpldqY nBB3Ijr9uKFlw== 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: Now that pages are "DMA-pinned" via pin_user_page*(), and unpinned via unpin_user_pages*(), we need some visibility into whether all of this is working correctly. Add two new fields to /proc/vmstat: nr_foll_pin_requested nr_foll_pin_returned These are documented in Documentation/core-api/pin_user_pages.rst. They represent the number of pages (since boot time) that have been pinned ("nr_foll_pin_requested") and unpinned ("nr_foll_pin_returned"), via pin_user_pages*() and unpin_user_pages*(). In the absence of long-running DMA or RDMA operations that hold pages pinned, the above two fields will normally be equal to each other. Signed-off-by: John Hubbard --- include/linux/mmzone.h | 2 ++ mm/gup.c | 21 +++++++++++++++++++++ mm/vmstat.c | 2 ++ 3 files changed, 25 insertions(+) diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 462f6873905a..392868bc4763 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -243,6 +243,8 @@ enum node_stat_item { NR_DIRTIED, /* page dirtyings since bootup */ NR_WRITTEN, /* page writings since bootup */ NR_KERNEL_MISC_RECLAIMABLE, /* reclaimable non-slab kernel pages */ + NR_FOLL_PIN_REQUESTED, /* via: pin_user_page(), gup flag: FOLL_PIN */ + NR_FOLL_PIN_RETURNED, /* pages returned via unpin_user_page() */ NR_VM_NODE_STAT_ITEMS }; =20 diff --git a/mm/gup.c b/mm/gup.c index 03e7a5cfa6a9..d536bda383c4 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -29,6 +29,19 @@ struct follow_page_context { unsigned int page_mask; }; =20 +#ifdef CONFIG_DEBUG_VM +static inline void __update_proc_vmstat(struct page *page, + enum node_stat_item item, int count) +{ + mod_node_page_state(page_pgdat(page), item, count); +} +#else +static inline void __update_proc_vmstat(struct page *page, + enum node_stat_item item, int count) +{ +} +#endif + static void hpage_pincount_add(struct page *page, int refs) { VM_BUG_ON_PAGE(!hpage_pincount_available(page), page); @@ -86,6 +99,8 @@ static __maybe_unused struct page *try_grab_compound_head= (struct page *page, if (flags & FOLL_GET) return try_get_compound_head(page, refs); else if (flags & FOLL_PIN) { + int orig_refs =3D refs; + /* * When pinning a compound page of order > 1 (which is what * hpage_pincount_available() checks for), use an exact count to @@ -104,6 +119,7 @@ static __maybe_unused struct page *try_grab_compound_he= ad(struct page *page, if (hpage_pincount_available(page)) hpage_pincount_add(page, refs); =20 + __update_proc_vmstat(page, NR_FOLL_PIN_REQUESTED, orig_refs); return page; } =20 @@ -159,6 +175,8 @@ bool __must_check try_grab_page(struct page *page, unsi= gned int flags) * once, so that the page really is pinned. */ page_ref_add(page, refs); + + __update_proc_vmstat(page, NR_FOLL_PIN_REQUESTED, 1); } =20 return true; @@ -179,6 +197,7 @@ static bool __unpin_devmap_managed_user_page(struct pag= e *page) =20 count =3D page_ref_sub_return(page, refs); =20 + __update_proc_vmstat(page, NR_FOLL_PIN_RETURNED, 1); /* * devmap page refcounts are 1-based, rather than 0-based: if * refcount is 1, then the page is free and the refcount is @@ -229,6 +248,8 @@ void unpin_user_page(struct page *page) =20 if (page_ref_sub_and_test(page, refs)) __put_page(page); + + __update_proc_vmstat(page, NR_FOLL_PIN_RETURNED, 1); } EXPORT_SYMBOL(unpin_user_page); =20 diff --git a/mm/vmstat.c b/mm/vmstat.c index 78d53378db99..b56808bae1b4 100644 --- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -1168,6 +1168,8 @@ const char * const vmstat_text[] =3D { "nr_dirtied", "nr_written", "nr_kernel_misc_reclaimable", + "nr_foll_pin_requested", + "nr_foll_pin_returned", =20 /* enum writeback_stat_item counters */ "nr_dirty_threshold", --=20 2.25.0