From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 76AAA2F7ACB; Tue, 16 Sep 2025 10:12:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758017544; cv=none; b=tEAJFonY7o8cd3rDEA3mWc8Ex87sDXmwSSKfkQutYw2w+LSAn5+R1vhOLMcLagRdJXGX0JNRgGa0ecgACGHvvJXvy/AtK6JT9iZMesATj+z2mGhs0AZ2CUgJW3ztqxd1QLJ4gDo/Nq34ucAOtBrh00vGbqcqkvghPmk8XgkkxeE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758017544; c=relaxed/simple; bh=+jBhf7v7FWI9SUvmU0eP8Ap7x6YsUlvlITRjlGy9t8M=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=AC/ZNedjtcFPy3KVHETDyoWmKClT4mZdxsGjdcUrcVel6twVjZgBtT6fh0HANAd9wDQeVKTNFYXxEFpoeFec6ekUdu3WwdARbdcfzcuvtihKdlyeSFZgRa7gtuQKXWeHBcfe17x8+6tNTZll9hPZi6dNWOmz81sVj9gyCcLgYAU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 35CE912FC; Tue, 16 Sep 2025 03:12:10 -0700 (PDT) Received: from [10.163.42.157] (unknown [10.163.42.157]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id BA3FE3F673; Tue, 16 Sep 2025 03:12:09 -0700 (PDT) Message-ID: Date: Tue, 16 Sep 2025 15:42:07 +0530 Precedence: bulk X-Mailing-List: linux-acpi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mm/memory-failure: Support disabling soft offline for HugeTLB pages To: Kyle Meyer , akpm@linux-foundation.org, corbet@lwn.net, david@redhat.com, linmiaohe@huawei.com, shuah@kernel.org, tony.luck@intel.com, jane.chu@oracle.com, jiaqiyan@google.com Cc: Liam.Howlett@oracle.com, bp@alien8.de, hannes@cmpxchg.org, jack@suse.cz, joel.granados@kernel.org, laoar.shao@gmail.com, lorenzo.stoakes@oracle.com, mclapinski@google.com, mhocko@suse.com, nao.horiguchi@gmail.com, osalvador@suse.de, rafael.j.wysocki@intel.com, rppt@kernel.org, russ.anderson@hpe.com, shawn.fan@intel.com, surenb@google.com, vbabka@suse.cz, linux-acpi@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org References: Content-Language: en-US From: Anshuman Khandual In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 16/09/25 5:57 AM, Kyle Meyer wrote: > Soft offlining a HugeTLB page reduces the HugeTLB page pool. > > Commit 56374430c5dfc ("mm/memory-failure: userspace controls soft-offlining pages") > introduced the following sysctl interface to control soft offline: > > /proc/sys/vm/enable_soft_offline > > The interface does not distinguish between page types: > > 0 - Soft offline is disabled > 1 - Soft offline is enabled > > Convert enable_soft_offline to a bitmask and support disabling soft > offline for HugeTLB pages: > > Bits: > > 0 - Enable soft offline > 1 - Disable soft offline for HugeTLB pages > > Supported values: > > 0 - Soft offline is disabled > 1 - Soft offline is enabled > 3 - Soft offline is enabled (disabled for HugeTLB pages) > > Existing behavior is preserved. > > Update documentation and HugeTLB soft offline self tests. > > Reported-by: Shawn Fan > Suggested-by: Tony Luck > Signed-off-by: Kyle Meyer > --- > > Tony's patch: > * https://lore.kernel.org/all/20250904155720.22149-1-tony.luck@intel.com > > v1: > * https://lore.kernel.org/all/aMGkAI3zKlVsO0S2@hpe.com > > v1 -> v2: > * Make the interface extensible, as suggested by David. > * Preserve existing behavior, as suggested by Jiaqi and David. > > Why clear errno in self tests? > > madvise() does not set errno when it's successful and errno is set by madvise() > during test_soft_offline_common(3) causing test_soft_offline_common(1) to fail: > > # Test soft-offline when enabled_soft_offline=1 > # Hugepagesize is 1048576kB > # enable_soft_offline => 1 > # Before MADV_SOFT_OFFLINE nr_hugepages=7 > # Allocated 0x80000000 bytes of hugetlb pages > # MADV_SOFT_OFFLINE 0x7fd600000000 ret=0, errno=95 > # MADV_SOFT_OFFLINE should ret 0 > # After MADV_SOFT_OFFLINE nr_hugepages=6 > not ok 2 Test soft-offline when enabled_soft_offline=1 > > --- > .../ABI/testing/sysfs-memory-page-offline | 3 ++ > Documentation/admin-guide/sysctl/vm.rst | 28 ++++++++++++++++--- > mm/memory-failure.c | 17 +++++++++-- > .../selftests/mm/hugetlb-soft-offline.c | 19 ++++++++++--- > 4 files changed, 56 insertions(+), 11 deletions(-) > > diff --git a/Documentation/ABI/testing/sysfs-memory-page-offline b/Documentation/ABI/testing/sysfs-memory-page-offline > index 00f4e35f916f..d3f05ed6605e 100644 > --- a/Documentation/ABI/testing/sysfs-memory-page-offline > +++ b/Documentation/ABI/testing/sysfs-memory-page-offline > @@ -20,6 +20,9 @@ Description: > number, or a error when the offlining failed. Reading > the file is not allowed. > > + Soft-offline can be controlled via sysctl, see: > + Documentation/admin-guide/sysctl/vm.rst > + This update is applicable right away without other changes proposed. Probably can be moved into a separate patch in itself ? > What: /sys/devices/system/memory/hard_offline_page > Date: Sep 2009 > KernelVersion: 2.6.33 > diff --git a/Documentation/admin-guide/sysctl/vm.rst b/Documentation/admin-guide/sysctl/vm.rst > index 4d71211fdad8..ace73480eb9d 100644 > --- a/Documentation/admin-guide/sysctl/vm.rst > +++ b/Documentation/admin-guide/sysctl/vm.rst > @@ -309,19 +309,39 @@ physical memory) vs performance / capacity implications in transparent and > HugeTLB cases. > > For all architectures, enable_soft_offline controls whether to soft offline > -memory pages. When set to 1, kernel attempts to soft offline the pages > -whenever it thinks needed. When set to 0, kernel returns EOPNOTSUPP to > -the request to soft offline the pages. Its default value is 1. > +memory pages. > + > +enable_soft_offline is a bitmask: > + > +Bits:: > + > + 0 - Enable soft offline > + 1 - Disable soft offline for HugeTLB pages > + > +Supported values:: > + > + 0 - Soft offline is disabled > + 1 - Soft offline is enabled > + 3 - Soft offline is enabled (disabled for HugeTLB pages) This looks very adhoc even though existing behavior is preserved. - Are HugeTLB pages the only page types to be considered ? - How the remaining bits here are going to be used later ? Also without a bit-wise usage roadmap, is not changing a procfs interface (ABI) bit problematic ? > + > +The default value is 1. > + > +If soft offline is disabled for the requested page type, EOPNOTSUPP is returned. > > It is worth mentioning that after setting enable_soft_offline to 0, the > following requests to soft offline pages will not be performed: > > +- Request to soft offline from sysfs (soft_offline_page). > + > - Request to soft offline pages from RAS Correctable Errors Collector. > > -- On ARM, the request to soft offline pages from GHES driver. > +- On ARM and X86, the request to soft offline pages from GHES driver. > > - On PARISC, the request to soft offline pages from Page Deallocation Table. > > +Note: > + Soft offlining a HugeTLB page reduces the HugeTLB page pool. > + > extfrag_threshold > ================= > > diff --git a/mm/memory-failure.c b/mm/memory-failure.c > index fc30ca4804bf..0ad9ae11d9e8 100644 > --- a/mm/memory-failure.c > +++ b/mm/memory-failure.c > @@ -64,11 +64,14 @@ > #include "internal.h" > #include "ras/ras_event.h" > > +#define SOFT_OFFLINE_ENABLED BIT(0) > +#define SOFT_OFFLINE_SKIP_HUGETLB BIT(1) > + > static int sysctl_memory_failure_early_kill __read_mostly; > > static int sysctl_memory_failure_recovery __read_mostly = 1; > > -static int sysctl_enable_soft_offline __read_mostly = 1; > +static int sysctl_enable_soft_offline __read_mostly = SOFT_OFFLINE_ENABLED; > > atomic_long_t num_poisoned_pages __read_mostly = ATOMIC_LONG_INIT(0); > > @@ -150,7 +153,7 @@ static const struct ctl_table memory_failure_table[] = { > .mode = 0644, > .proc_handler = proc_dointvec_minmax, > .extra1 = SYSCTL_ZERO, > - .extra2 = SYSCTL_ONE, > + .extra2 = SYSCTL_THREE, > } > }; > > @@ -2799,12 +2802,20 @@ int soft_offline_page(unsigned long pfn, int flags) > return -EIO; > } > > - if (!sysctl_enable_soft_offline) { > + if (!(sysctl_enable_soft_offline & SOFT_OFFLINE_ENABLED)) { > pr_info_once("disabled by /proc/sys/vm/enable_soft_offline\n"); > put_ref_page(pfn, flags); > return -EOPNOTSUPP; > } > > + if (sysctl_enable_soft_offline & SOFT_OFFLINE_SKIP_HUGETLB) { > + if (folio_test_hugetlb(pfn_folio(pfn))) { > + pr_info_once("disabled for HugeTLB pages by /proc/sys/vm/enable_soft_offline\n"); > + put_ref_page(pfn, flags); > + return -EOPNOTSUPP; > + } > + } > + > mutex_lock(&mf_mutex); > > if (PageHWPoison(page)) { > diff --git a/tools/testing/selftests/mm/hugetlb-soft-offline.c b/tools/testing/selftests/mm/hugetlb-soft-offline.c > index f086f0e04756..b87c8778cadf 100644 > --- a/tools/testing/selftests/mm/hugetlb-soft-offline.c > +++ b/tools/testing/selftests/mm/hugetlb-soft-offline.c > @@ -5,6 +5,8 @@ > * offlining failed with EOPNOTSUPP. > * - if enable_soft_offline = 1, a hugepage should be dissolved and > * nr_hugepages/free_hugepages should be reduced by 1. > + * - if enable_soft_offline = 3, hugepages should stay intact and soft > + * offlining failed with EOPNOTSUPP. > * > * Before running, make sure more than 2 hugepages of default_hugepagesz > * are allocated. For example, if /proc/meminfo/Hugepagesize is 2048kB: > @@ -32,6 +34,9 @@ > > #define EPREFIX " !!! " > > +#define SOFT_OFFLINE_ENABLED (1 << 0) > +#define SOFT_OFFLINE_SKIP_HUGETLB (1 << 1) > + > static int do_soft_offline(int fd, size_t len, int expect_errno) > { > char *filemap = NULL; > @@ -56,6 +61,7 @@ static int do_soft_offline(int fd, size_t len, int expect_errno) > ksft_print_msg("Allocated %#lx bytes of hugetlb pages\n", len); > > hwp_addr = filemap + len / 2; > + errno = 0; > ret = madvise(hwp_addr, pagesize, MADV_SOFT_OFFLINE); > ksft_print_msg("MADV_SOFT_OFFLINE %p ret=%d, errno=%d\n", > hwp_addr, ret, errno); > @@ -83,7 +89,7 @@ static int set_enable_soft_offline(int value) > char cmd[256] = {0}; > FILE *cmdfile = NULL; > > - if (value != 0 && value != 1) > + if (value < 0 || value > 3) > return -EINVAL; > > sprintf(cmd, "echo %d > /proc/sys/vm/enable_soft_offline", value); > @@ -155,13 +161,17 @@ static int create_hugetlbfs_file(struct statfs *file_stat) > static void test_soft_offline_common(int enable_soft_offline) > { > int fd; > - int expect_errno = enable_soft_offline ? 0 : EOPNOTSUPP; > + int expect_errno = 0; > struct statfs file_stat; > unsigned long hugepagesize_kb = 0; > unsigned long nr_hugepages_before = 0; > unsigned long nr_hugepages_after = 0; > int ret; > > + if (!(enable_soft_offline & SOFT_OFFLINE_ENABLED) || > + (enable_soft_offline & SOFT_OFFLINE_SKIP_HUGETLB)) > + expect_errno = EOPNOTSUPP; > + > ksft_print_msg("Test soft-offline when enabled_soft_offline=%d\n", > enable_soft_offline); > > @@ -198,7 +208,7 @@ static void test_soft_offline_common(int enable_soft_offline) > // No need for the hugetlbfs file from now on. > close(fd); > > - if (enable_soft_offline) { > + if (expect_errno == 0) { > if (nr_hugepages_before != nr_hugepages_after + 1) { > ksft_test_result_fail("MADV_SOFT_OFFLINE should reduced 1 hugepage\n"); > return; > @@ -219,8 +229,9 @@ static void test_soft_offline_common(int enable_soft_offline) > int main(int argc, char **argv) > { > ksft_print_header(); > - ksft_set_plan(2); > + ksft_set_plan(3); > > + test_soft_offline_common(3); > test_soft_offline_common(1); > test_soft_offline_common(0); >