From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-185.mta0.migadu.com (out-185.mta0.migadu.com [91.218.175.185]) (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 DB7B61F03D2 for ; Fri, 13 Feb 2026 07:19:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.185 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770967145; cv=none; b=mD7A6OtMXzFuGieL0eqVjceHXIpD0oKb9TIirUyQZEAffz+qHRZrH5bJRvHgOIPIsfkgnN0E99/ghyrbWzK8dRNpks68JUy4LoYstQwjp9q/vZewbSBxLmgzO6YCs9+RKxKTa7EqOOjbu7LXD2l3WILlr7fQJ8GHeE5+RTL3HbM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770967145; c=relaxed/simple; bh=3FbY3oiUDhxvvJsY+ZzL8u6BhbEXlfel5ApzMIwducM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Eaz6bIG4bomrAfcsRgOT/dzGvJ/V1b7QDy4xJ/f8ghX899VTLZC3ky6u+Qawh/gk5o4xRA5RQUP92o29QZrdw5UZ296p/fW/48TT1LhcaXeC1DKa7ooeWX+HXToy1Ps408vn44GOP5rZdo3SMf5tNJlRxB9EYnAWWyHfUZl/wrU= 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=lIXNPvSq; arc=none smtp.client-ip=91.218.175.185 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="lIXNPvSq" 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=1770967140; 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=fHxD0q/WzMwerrB6ZvB9y/vH4lR5GGZkuNBvcMrlqCg=; b=lIXNPvSqtq/mhCIHqxeszIYr/dYCcHPhuKv8BU2LzkjdLcK9P1zVhUyLfgrTBtWksG2iM/ Cd9uWmaQOjCZeDqnMhBfEkW5CxhEcfoN0N8H3l5JRit/TmtkhvnztmxIr2KOWqN/FtKzwx XJKKxxEqFXLCORDZbvr0dcqUqxpn4b4= From: Jiayuan Chen To: linux-mm@kvack.org Cc: jiayuan.chen@linux.dev, Jiayuan Chen , Shakeel Butt , Nhat Pham , SeongJae Park , Tejun Heo , Johannes Weiner , =?UTF-8?q?Michal=20Koutn=C3=BD?= , Jonathan Corbet , Michal Hocko , Roman Gushchin , Muchun Song , Andrew Morton , Yosry Ahmed , 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 mm-new v3 2/2] selftests/cgroup: add test for zswap incompressible pages Date: Fri, 13 Feb 2026 15:18:23 +0800 Message-ID: <20260213071827.5688-3-jiayuan.chen@linux.dev> In-Reply-To: <20260213071827.5688-1-jiayuan.chen@linux.dev> References: <20260213071827.5688-1-jiayuan.chen@linux.dev> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT 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=/dev/zero of=/swapfile bs=1M count=2048 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 Acked-by: Shakeel Butt Acked-by: Nhat Pham Reviewed-by: SeongJae Park Signed-off-by: Jiayuan Chen --- tools/testing/selftests/cgroup/test_zswap.c | 136 ++++++++++++++++++++ 1 file changed, 136 insertions(+) diff --git a/tools/testing/selftests/cgroup/test_zswap.c b/tools/testing/selftests/cgroup/test_zswap.c index 64ebc3f3f203..a7bdcdd09d62 100644 --- a/tools/testing/selftests/cgroup/test_zswap.c +++ b/tools/testing/selftests/cgroup/test_zswap.c @@ -5,6 +5,8 @@ #include #include #include +#include +#include #include #include #include @@ -574,6 +576,139 @@ static int test_no_kmem_bypass(const char *root) return ret; } +struct incomp_child_args { + size_t size; + int pipefd[2]; + int madvise_ret; + int madvise_errno; +}; + +static int allocate_random_and_wait(const char *cgroup, void *arg) +{ + struct incomp_child_args *values = arg; + size_t size = values->size; + char *mem; + int fd; + ssize_t n; + + close(values->pipefd[0]); + + mem = mmap(NULL, size, PROT_READ | PROT_WRITE, + MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); + if (mem == MAP_FAILED) + return -1; + + /* Fill with random data from /dev/urandom - incompressible */ + fd = open("/dev/urandom", O_RDONLY); + if (fd < 0) { + munmap(mem, size); + return -1; + } + + for (size_t i = 0; i < size; ) { + n = read(fd, mem + i, size - i); + if (n <= 0) + break; + i += n; + } + close(fd); + + /* Touch all pages to ensure they're faulted in */ + for (size_t i = 0; i < size; i += PAGE_SIZE) + mem[i] = mem[i]; + + /* Use MADV_PAGEOUT to push pages into zswap */ + values->madvise_ret = madvise(mem, size, MADV_PAGEOUT); + values->madvise_errno = errno; + + /* Notify parent that allocation and pageout are done */ + write(values->pipefd[1], "x", 1); + close(values->pipefd[1]); + + /* Keep memory alive for parent to check stats */ + pause(); + munmap(mem, size); + 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_incomp. + * + * The child process allocates random data within memory.max, then uses + * MADV_PAGEOUT to push pages into zswap. The parent waits on a pipe for + * the child to finish, then checks the zswap_incomp stat before the child + * exits (zswap_incomp is a gauge that decreases on free). + */ +static int test_zswap_incompressible(const char *root) +{ + int ret = KSFT_FAIL; + struct incomp_child_args *values; + char *test_group; + long zswap_incomp; + pid_t child_pid; + int child_status; + char buf; + + values = mmap(0, sizeof(struct incomp_child_args), PROT_READ | + PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS, -1, 0); + if (values == MAP_FAILED) + return KSFT_FAIL; + + if (pipe(values->pipefd)) { + munmap(values, sizeof(struct incomp_child_args)); + return KSFT_FAIL; + } + + test_group = 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; + + values->size = MB(4); + child_pid = cg_run_nowait(test_group, allocate_random_and_wait, values); + if (child_pid < 0) + goto out; + + close(values->pipefd[1]); + + /* Wait for child to finish allocating and pageout */ + read(values->pipefd[0], &buf, 1); + close(values->pipefd[0]); + + zswap_incomp = get_zswap_incomp(test_group); + if (zswap_incomp <= 0) { + long zswpout = get_zswpout(test_group); + long zswapped = cg_read_key_long(test_group, "memory.stat", "zswapped "); + long zswap_b = cg_read_key_long(test_group, "memory.stat", "zswap "); + + ksft_print_msg("zswap_incomp not increased: %ld\n", zswap_incomp); + ksft_print_msg("debug: zswpout=%ld zswapped=%ld zswap_b=%ld\n", + zswpout, zswapped, zswap_b); + ksft_print_msg("debug: madvise ret=%d errno=%d\n", + values->madvise_ret, values->madvise_errno); + goto out_kill; + } + + ret = KSFT_PASS; + +out_kill: + kill(child_pid, SIGTERM); + waitpid(child_pid, &child_status, 0); +out: + cg_destroy(test_group); + free(test_group); + munmap(values, sizeof(struct incomp_child_args)); + return ret; +} + #define T(x) { x, #x } struct zswap_test { int (*fn)(const char *root); @@ -586,6 +721,7 @@ 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 -- 2.43.0