From nobody Fri Apr 3 01:22:50 2026 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 8A4B0346A0B for ; Thu, 2 Apr 2026 06:38:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775111913; cv=none; b=odx+GeSrHP0w004anDZrEyE1SeyM6U683pJilIMe6LaHG9/y7OCd43QB2htEgEt8p8RcZZqC37TknM6xK5Uv1VptBw9xwGRGAWcDs8bkWkFvzc4hrT1H0nZCr8rKf6zfrNoO9duvot1e/O5R8gdjOD5lseJs3yqUl8G9reIgOaY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775111913; c=relaxed/simple; bh=Lc5dBL8pYJp+rq6/inASVmhrpfGTGZtDvbKk/Z72eNM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=l5YUJS37sk/hCbd0qG6Qp57Tb/+aq++hiqoADG/7WodKf6HiZWogEGThROaKBOs3C0h0RhA/LvhHeMXxm2+8l87UCFYrX8ulYJfbllttCXMFkgQ5SHHhgcgf3mU+WdqCK0U+p6O/1ewWXXcMXKjYOYoOFtKwiCvl38WGsIQU55w= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=bLvfyd/8; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="bLvfyd/8" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1775111910; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=ugd9P0cI6Fe499qy5Kl/bBLKO3rB+If5FXFztZIJJ9w=; b=bLvfyd/8s+MWxlJEvi/64oIJgmtVxw50qiUnJMbau1/qBNOQmMo60rg5+tUMLOlW3/SYgf zGw9huU1r/M2ug90hETIGJK3XDfoHnar4vw42b7Sau70TvBinD+1+oSEIAAbxQVzi3UuaS HTBay9bC0WykzJGOaTAalTXQHa5epOA= Received: from mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-283-tJ1hc58aOiWuTcCCJ9kzNQ-1; Thu, 02 Apr 2026 02:38:28 -0400 X-MC-Unique: tJ1hc58aOiWuTcCCJ9kzNQ-1 X-Mimecast-MFC-AGG-ID: tJ1hc58aOiWuTcCCJ9kzNQ_1775111905 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 013F5195607B; Thu, 2 Apr 2026 06:38:25 +0000 (UTC) Received: from fedora-laptop-x1.redhat.com (unknown [10.72.112.158]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 1CC781800351; Thu, 2 Apr 2026 06:38:15 +0000 (UTC) From: Li Wang To: akpm@linux-foundation.org, rppt@kernel.org, david@kernel.org, hannes@cmpxchg.org, yosry@kernel.org, ljs@kernel.org, Liam.Howlett@oracle.com, mhocko@suse.com, shuah@kernel.org, chengming.zhou@linux.dev, longman@redhat.com, nphamcs@gmail.com Cc: linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Michal Hocko , =?UTF-8?q?Michal=20Koutn=C3=BD?= , Muchun Song , Tejun Heo , Roman Gushchin , Shakeel Butt , Yosry Ahmed Subject: [PATCH v6 6/8] selftest/cgroup: fix zswap test_no_invasive_cgroup_shrink on large pagesize system Date: Thu, 2 Apr 2026 14:37:12 +0800 Message-ID: <20260402063714.55124-7-liwang@redhat.com> In-Reply-To: <20260402063714.55124-1-liwang@redhat.com> References: <20260402063714.55124-1-liwang@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 test_no_invasive_cgroup_shrink sets up two cgroups: wb_group, which is expected to trigger zswap writeback, and a control group (renamed to zw_group), which should only have pages sitting in zswap without any writeback. There are two problems with the current test: 1) The data patterns are reversed. wb_group uses allocate_bytes(), which writes only a single byte per page =E2=80=94 trivially compressible, especially by zstd =E2=80=94 so compressed pages fit within zswap.max and writeback is never triggered. Meanwhile, the control group uses getrandom() to produce hard-to-compress data, but it is the group that does *not* need writeback. 2) The test uses fixed sizes (10K zswap.max, 10MB allocation) that are too small on systems with large PAGE_SIZE (e.g. 64K), failing to build enough memory pressure to trigger writeback reliably. Fix both issues by: - Swapping the data patterns: fill wb_group pages with partially random data (getrandom for page_size/4 bytes) to resist compression and trigger writeback, and fill zw_group pages with simple repeated data to stay compressed in zswap. - Making all size parameters PAGE_SIZE-aware: set allocation size to PAGE_SIZE * 1024, memory.zswap.max to PAGE_SIZE, and memory.max to allocation_size / 2 for both cgroups. - Allocating memory inline instead of via cg_run() so the pages remain resident throughout the test. =3D=3D=3D Error Log =3D=3D=3D # getconf PAGESIZE 65536 # ./test_zswap TAP version 13 ... ok 5 test_zswap_writeback_disabled ok 6 # SKIP test_no_kmem_bypass not ok 7 test_no_invasive_cgroup_shrink Signed-off-by: Li Wang Cc: Johannes Weiner Cc: Michal Hocko Cc: Michal Koutn=C3=BD Cc: Muchun Song Cc: Nhat Pham Cc: Tejun Heo Cc: Roman Gushchin Cc: Shakeel Butt Cc: Yosry Ahmed --- Notes: v5: - Swap data patterns: use getrandom() for wb_group and simple memset for zw_group to fix the reversed allocation logic. - Rename control_group to zw_group for clarity. - Allocate memory inline instead of via cg_run() so pages remain resident throughout the test. tools/testing/selftests/cgroup/test_zswap.c | 70 ++++++++++++++------- 1 file changed, 49 insertions(+), 21 deletions(-) diff --git a/tools/testing/selftests/cgroup/test_zswap.c b/tools/testing/se= lftests/cgroup/test_zswap.c index db4889bef6d4..2b14683f9a77 100644 --- a/tools/testing/selftests/cgroup/test_zswap.c +++ b/tools/testing/selftests/cgroup/test_zswap.c @@ -9,6 +9,7 @@ #include #include #include +#include =20 #include "kselftest.h" #include "cgroup_util.h" @@ -424,44 +425,71 @@ static int test_zswap_writeback_disabled(const char *= root) static int test_no_invasive_cgroup_shrink(const char *root) { int ret =3D KSFT_FAIL; - size_t control_allocation_size =3D MB(10); - char *control_allocation =3D NULL, *wb_group =3D NULL, *control_group =3D= NULL; + unsigned int off; + size_t allocation_size =3D page_size * 1024; + unsigned int nr_pages =3D allocation_size / page_size; + char zswap_max_buf[32], mem_max_buf[32]; + char *zw_allocation =3D NULL, *wb_allocation =3D NULL; + char *zw_group =3D NULL, *wb_group =3D NULL; + + snprintf(zswap_max_buf, sizeof(zswap_max_buf), "%d", page_size); + snprintf(mem_max_buf, sizeof(mem_max_buf), "%zu", allocation_size / 2); =20 wb_group =3D setup_test_group_1M(root, "per_memcg_wb_test1"); if (!wb_group) return KSFT_FAIL; - if (cg_write(wb_group, "memory.zswap.max", "10K")) + if (cg_write(wb_group, "memory.zswap.max", zswap_max_buf)) + goto out; + if (cg_write(wb_group, "memory.max", mem_max_buf)) + goto out; + + zw_group =3D setup_test_group_1M(root, "per_memcg_wb_test2"); + if (!zw_group) goto out; - control_group =3D setup_test_group_1M(root, "per_memcg_wb_test2"); - if (!control_group) + if (cg_write(zw_group, "memory.max", mem_max_buf)) goto out; =20 - /* Push some test_group2 memory into zswap */ - if (cg_enter_current(control_group)) + /* Push some zw_group memory into zswap (simple data, easy to compress) */ + if (cg_enter_current(zw_group)) goto out; - control_allocation =3D malloc(control_allocation_size); - for (int i =3D 0; i < control_allocation_size; i +=3D page_size) - control_allocation[i] =3D 'a'; - if (cg_read_key_long(control_group, "memory.stat", "zswapped") < 1) + zw_allocation =3D malloc(allocation_size); + for (int i =3D 0; i < nr_pages; i++) { + off =3D (unsigned long)i * page_size; + memset(&zw_allocation[off], 0, page_size); + memset(&zw_allocation[off], 'a', page_size/4); + } + if (cg_read_key_long(zw_group, "memory.stat", "zswapped") < 1) goto out; =20 - /* Allocate 10x memory.max to push wb_group memory into zswap and trigger= wb */ - if (cg_run(wb_group, allocate_bytes, (void *)MB(10))) + /* Push wb_group memory into zswap with hard-to-compress data to trigger = wb */ + if (cg_enter_current(wb_group)) + goto out; + wb_allocation =3D malloc(allocation_size); + if (!wb_allocation) goto out; + for (int i =3D 0; i < nr_pages; i++) { + off =3D (unsigned long)i * page_size; + memset(&wb_allocation[off], 0, page_size); + getrandom(&wb_allocation[off], page_size/4, 0); + } =20 /* Verify that only zswapped memory from gwb_group has been written back = */ - if (get_cg_wb_count(wb_group) > 0 && get_cg_wb_count(control_group) =3D= =3D 0) + if (get_cg_wb_count(wb_group) > 0 && get_cg_wb_count(zw_group) =3D=3D 0) ret =3D KSFT_PASS; out: cg_enter_current(root); - if (control_group) { - cg_destroy(control_group); - free(control_group); + if (zw_group) { + cg_destroy(zw_group); + free(zw_group); + } + if (wb_group) { + cg_destroy(wb_group); + free(wb_group); } - cg_destroy(wb_group); - free(wb_group); - if (control_allocation) - free(control_allocation); + if (zw_allocation) + free(zw_allocation); + if (wb_allocation) + free(wb_allocation); return ret; } =20 --=20 2.53.0