From nobody Sat Feb 7 21:30:33 2026 Received: from out-177.mta1.migadu.com (out-177.mta1.migadu.com [95.215.58.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E5E9730AD1D; Fri, 6 Feb 2026 07:22:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.177 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770362568; cv=none; b=Kh3kHbQ15qHJXwck4bMvW0w0fRmxZZdEsjxiKzXQH/BRTOhWqpZRRoGe6W+HjXuRL6rWFs/4qrPh27dpRVtgEA9AMAPZ718BZcxOmyAInD/q/dMLyYDhGPeix23f9PTn7FfKAwVoPIKxGNf4E19KH5WrIfYOFJ1Qs7HBunp/3u4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770362568; c=relaxed/simple; bh=W7Pj5IOXmHNCfVzPNifKS2LnKgE5X8L1spcNsvgNAyA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ZMlB3JILTc7ZWVrFak+8g0pP0q0t1vF/NAqWvhJwfJc3rYE/Lcx4fG/N78DRBomg+dcTl4BOafJrhJ/2ml6wK4r+HYA1o+DoEJXuQB/wPX3G9Q728rGvLnFWVX1L1lhTUzKMi/y+x4j7wFtzUmX1lDryePlgLNj5TK0WGQdDv04= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=K+C4Ejc5; arc=none smtp.client-ip=95.215.58.177 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="K+C4Ejc5" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1770362566; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=QVhNoOKTqhs5FIM84PwOapldZJ1EjdC0zJo6ufYFyUo=; b=K+C4Ejc5kYVa1AMupNC5l8ot9jFScgXyb+D+zIw9ZBvY3NiXL0rK4kEbWmFA7i7a1LUKEa 8/aC154zcQVvLVXsflxO27dIvGWhoyBQ8v3NYygtLhMZecbpziRI9uYqN2sJFcY5KWYXcX 97o64Jq7iwPbBEtR111+cZx2n28j/rk= From: Jiayuan Chen To: linux-mm@kvack.org Cc: Jiayuan Chen , Tejun Heo , Johannes Weiner , =?UTF-8?q?Michal=20Koutn=C3=BD?= , Jonathan Corbet , Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Andrew Morton , Yosry Ahmed , Nhat Pham , Chengming Zhou , Shuah Khan , cgroups@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: [PATCH v2 2/2] selftests/cgroup: add test for zswap incompressible pages Date: Fri, 6 Feb 2026 15:22:16 +0800 Message-ID: <20260206072220.144008-3-jiayuan.chen@linux.dev> In-Reply-To: <20260206072220.144008-1-jiayuan.chen@linux.dev> References: <20260206072220.144008-1-jiayuan.chen@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Migadu-Flow: FLOW_OUT Content-Type: text/plain; charset="utf-8" From: Jiayuan Chen Add test_zswap_incompressible() to verify that the zswap_incomp memcg stat correctly tracks incompressible pages. The test allocates memory filled with random data from /dev/urandom, which cannot be effectively compressed by zswap. When this data is swapped out to zswap, it should be stored as-is and tracked by the zswap_incomp counter. The test verifies that: 1. Pages are swapped out to zswap (zswpout increases) 2. Incompressible pages are tracked (zswap_incomp increases) test: dd if=3D/dev/zero of=3D/swapfile bs=3D1M count=3D2048 chmod 600 /swapfile mkswap /swapfile swapon /swapfile echo Y > /sys/module/zswap/parameters/enabled ./test_zswap TAP version 13 1..8 ok 1 test_zswap_usage ok 2 test_swapin_nozswap ok 3 test_zswapin ok 4 test_zswap_writeback_enabled ok 5 test_zswap_writeback_disabled ok 6 test_no_kmem_bypass ok 7 test_no_invasive_cgroup_shrink ok 8 test_zswap_incompressible Totals: pass:8 fail:0 xfail:0 xpass:0 skip:0 error:0 Signed-off-by: Jiayuan Chen Acked-by: Nhat Pham Acked-by: Shakeel Butt Reviewed-by: SeongJae Park --- tools/testing/selftests/cgroup/test_zswap.c | 96 +++++++++++++++++++++ 1 file changed, 96 insertions(+) diff --git a/tools/testing/selftests/cgroup/test_zswap.c b/tools/testing/se= lftests/cgroup/test_zswap.c index 64ebc3f3f203..8cb8a131357d 100644 --- a/tools/testing/selftests/cgroup/test_zswap.c +++ b/tools/testing/selftests/cgroup/test_zswap.c @@ -5,6 +5,7 @@ #include #include #include +#include #include #include #include @@ -574,6 +575,100 @@ static int test_no_kmem_bypass(const char *root) return ret; } =20 +static int allocate_random_and_wait(const char *cgroup, void *arg) +{ + size_t size =3D (size_t)arg; + char *mem; + int fd; + ssize_t n; + + mem =3D malloc(size); + if (!mem) + return -1; + + /* Fill with random data from /dev/urandom - incompressible */ + fd =3D open("/dev/urandom", O_RDONLY); + if (fd < 0) { + free(mem); + return -1; + } + + for (size_t i =3D 0; i < size; ) { + n =3D read(fd, mem + i, size - i); + if (n <=3D 0) + break; + i +=3D n; + } + close(fd); + + /* Touch all pages to ensure they're faulted in */ + for (size_t i =3D 0; i < size; i +=3D 4096) + mem[i] =3D mem[i]; + + /* Keep memory alive for parent to reclaim and check stats */ + pause(); + free(mem); + return 0; +} + +static long get_zswap_incomp(const char *cgroup) +{ + return cg_read_key_long(cgroup, "memory.stat", "zswap_incomp "); +} + +/* + * Test that incompressible pages (random data) are tracked by zswap_incom= p. + * + * Since incompressible pages stored in zswap are charged at full PAGE_SIZE + * (no memory savings), we cannot rely on memory.max pressure to push them + * into zswap. Instead, we allocate random data within memory.max, then use + * memory.reclaim to proactively push pages into zswap while checking the = stat + * before the child exits (zswap_incomp is a gauge that decreases on free). + */ +static int test_zswap_incompressible(const char *root) +{ + int ret =3D KSFT_FAIL; + char *test_group; + long zswap_incomp; + pid_t child_pid; + int child_status; + + test_group =3D cg_name(root, "zswap_incompressible_test"); + if (!test_group) + goto out; + if (cg_create(test_group)) + goto out; + if (cg_write(test_group, "memory.max", "32M")) + goto out; + + child_pid =3D cg_run_nowait(test_group, allocate_random_and_wait, + (void *)MB(4)); + if (child_pid < 0) + goto out; + + /* Wait for child to finish allocating */ + usleep(500000); + + /* Proactively reclaim to push random pages into zswap */ + cg_write_numeric(test_group, "memory.reclaim", MB(4)); + + zswap_incomp =3D get_zswap_incomp(test_group); + if (zswap_incomp <=3D 0) { + ksft_print_msg("zswap_incomp not increased: %ld\n", zswap_incomp); + goto out_kill; + } + + ret =3D KSFT_PASS; + +out_kill: + kill(child_pid, SIGTERM); + waitpid(child_pid, &child_status, 0); +out: + cg_destroy(test_group); + free(test_group); + return ret; +} + #define T(x) { x, #x } struct zswap_test { int (*fn)(const char *root); @@ -586,6 +681,7 @@ struct zswap_test { T(test_zswap_writeback_disabled), T(test_no_kmem_bypass), T(test_no_invasive_cgroup_shrink), + T(test_zswap_incompressible), }; #undef T =20 --=20 2.43.0