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Howlett , ryan.roberts@arm.com, Vlastimil Babka , lance.yang@linux.dev, linux-kernel@vger.kernel.org, nphamcs@gmail.com, shikemeng@huaweicloud.com, yosry@kernel.org, qi.zheng@linux.dev, luizcap@redhat.com, kernel-team@meta.com, Usama Arif Subject: [PATCH v9 18/32] fs/proc: account PMD swap entries in smaps Date: Thu, 5 Nov 2026 10:39:02 -0800 Message-ID: <20261105183940.2236717-19-usama.arif@linux.dev> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261105183940.2236717-1-usama.arif@linux.dev> References: <20261105183940.2236717-1-usama.arif@linux.dev> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit smaps_pmd_entry() derives a page from a non-present PMD and gives up if it cannot. A PMD swap entry carries no PFN, so a swapped-out THP is missing from both Swap and SwapPss. The slots of a PMD swap entry can have different swap reference counts, so SwapPss has to be computed one slot at a time rather than divided once. Factor that loop out of smaps_pte_entry() and call it from both levels, then return early: a swapped-out THP is not resident and must not be added to AnonHugePages or Rss. While touching PMD softleaf accounting, match the PTE path and treat device-private PMD entries as fake-present. This lets smaps use mapcount-based PSS and private/shared accounting instead of treating them like migration entries. Signed-off-by: Usama Arif --- fs/proc/task_mmu.c | 41 ++++++++++++++++++++++++++++------------- 1 file changed, 28 insertions(+), 13 deletions(-) diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index 22361607020d1..bfe9d6af76d5a 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -965,6 +965,25 @@ static void smaps_pte_hole_lookup(unsigned long addr, struct mm_walk *walk) #endif } +static void smaps_account_swap(struct mem_size_stats *mss, + softleaf_t entry, unsigned long nr_pages) +{ + mss->swap += nr_pages << PAGE_SHIFT; + do { + int swapcount = swp_swapcount(entry); + + if (swapcount >= 2) { + u64 pss_delta = (u64)PAGE_SIZE << PSS_SHIFT; + + do_div(pss_delta, swapcount); + mss->swap_pss += pss_delta; + } else { + mss->swap_pss += (u64)PAGE_SIZE << PSS_SHIFT; + } + entry.val++; + } while (--nr_pages); +} + static void smaps_pte_entry(pte_t *pte, unsigned long addr, struct mm_walk *walk) { @@ -986,18 +1005,7 @@ static void smaps_pte_entry(pte_t *pte, unsigned long addr, const softleaf_t entry = softleaf_from_pte(ptent); if (softleaf_is_swap(entry)) { - int mapcount; - - mss->swap += PAGE_SIZE; - mapcount = swp_swapcount(entry); - if (mapcount >= 2) { - u64 pss_delta = (u64)PAGE_SIZE << PSS_SHIFT; - - do_div(pss_delta, mapcount); - mss->swap_pss += pss_delta; - } else { - mss->swap_pss += (u64)PAGE_SIZE << PSS_SHIFT; - } + smaps_account_swap(mss, entry, 1); } else if (softleaf_has_pfn(entry)) { if (softleaf_is_device_private(entry)) present = true; @@ -1030,8 +1038,15 @@ static void smaps_pmd_entry(pmd_t *pmd, unsigned long addr, } else if (unlikely(thp_migration_supported())) { const softleaf_t entry = softleaf_from_pmd(*pmd); - if (softleaf_has_pfn(entry)) + if (softleaf_is_swap(entry)) { + smaps_account_swap(mss, entry, HPAGE_PMD_NR); + return; + } + if (softleaf_has_pfn(entry)) { + if (softleaf_is_device_private(entry)) + present = true; page = softleaf_to_page(entry); + } } if (IS_ERR_OR_NULL(page)) return; -- 2.53.0-Meta