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Tue, 25 Aug 2026 08:32:54 -0700 (PDT) From: Nhat Pham To: akpm@linux-foundation.org Cc: chrisl@kernel.org, kasong@tencent.com, hannes@cmpxchg.org, mhocko@kernel.org, roman.gushchin@linux.dev, shakeel.butt@linux.dev, yosry@kernel.org, david@kernel.org, muchun.song@linux.dev, shikemeng@huaweicloud.com, baoquan.he@linux.dev, baohua@kernel.org, youngjun.park@lge.com, chengming.zhou@linux.dev, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, qi.zheng@linux.dev, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, riel@surriel.com, gourry@gourry.net, haowenchao22@gmail.com, corbet@lwn.net, hughd@google.com, baolin.wang@linux.alibaba.com, tj@kernel.org, mkoutny@suse.com, skhan@linuxfoundation.org, kunwu.chan@linux.dev, kernel-team@meta.com, nphamcs@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, cgroups@vger.kernel.org Subject: [PATCH v4 09/11] mm, swap: add debugfs counters for vswap Date: Tue, 25 Aug 2026 08:32:35 -0700 Message-ID: <20260825153238.2695446-10-nphamcs@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260825153238.2695446-1-nphamcs@gmail.com> References: <20260825153238.2695446-1-nphamcs@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: AAD1840013 X-Stat-Signature: dohhic5p3w5t39858mgqr4cwphippfye X-HE-Tag: 1787671976-25872 X-HE-Meta: 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 xxBAu6fz 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Add /sys/kernel/debug/vswap/ with two counters: * used: virtual swap slots (pages) currently allocated * alloc_reject: cumulative pages that failed to get a vswap slot Signed-off-by: Nhat Pham --- mm/swapfile.c | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) diff --git a/mm/swapfile.c b/mm/swapfile.c index 517fa58f8022..3b10173cddc3 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -7,6 +7,7 @@ */ #include +#include #include #include #include @@ -142,6 +143,8 @@ static DEFINE_PER_CPU(struct percpu_vswap_cluster, percpu_vswap_cluster) = { .lock = INIT_LOCAL_LOCK(), }; +static atomic_long_t vswap_alloc_reject = ATOMIC_LONG_INIT(0); + static bool vswap_alloc(struct folio *folio); static void vswap_mark_cache_only(struct swap_cluster_info *ci, unsigned int ci_off); @@ -1983,6 +1986,7 @@ static bool vswap_alloc(struct folio *folio) this_cpu_write(percpu_vswap_cluster.offset[order], SWAP_ENTRY_INVALID); local_unlock(&percpu_vswap_cluster.lock); + atomic_long_add(folio_nr_pages(folio), &vswap_alloc_reject); return false; } @@ -4795,9 +4799,25 @@ early_param("vswap", early_vswap); /* vswap does no IO on its own. */ static const struct swap_ops vswap_ops = { }; +static int vswap_used_get(void *data, u64 *val) +{ + *val = swap_usage_in_pages(vswap_si); + return 0; +} +DEFINE_DEBUGFS_ATTRIBUTE(vswap_used_fops, vswap_used_get, NULL, "%llu\n"); + +static int vswap_alloc_reject_get(void *data, u64 *val) +{ + *val = atomic_long_read(&vswap_alloc_reject); + return 0; +} +DEFINE_DEBUGFS_ATTRIBUTE(vswap_alloc_reject_fops, vswap_alloc_reject_get, NULL, + "%llu\n"); + static int __init vswap_init(void) { struct swap_info_struct *si; + struct dentry *root; unsigned long maxpages; int err; @@ -4841,6 +4861,12 @@ static int __init vswap_init(void) mutex_unlock(&swapon_mutex); vswap_si = si; + + root = debugfs_create_dir("vswap", NULL); + debugfs_create_file("used", 0444, root, NULL, &vswap_used_fops); + debugfs_create_file("alloc_reject", 0444, root, NULL, + &vswap_alloc_reject_fops); + pr_info("vswap: created virtual swap device (%lu pages)\n", maxpages); /* Last: everything above must be visible before routing starts. */ -- 2.53.0-Meta