From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michal Hocko Subject: [PATCH 3/3] mm, proc: report PR_SET_THP_DISABLE in proc Date: Tue, 11 Dec 2018 15:36:41 +0100 Message-ID: <20181211143641.3503-4-mhocko@kernel.org> References: <20181211143641.3503-1-mhocko@kernel.org> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <20181211143641.3503-1-mhocko@kernel.org> Sender: linux-kernel-owner@vger.kernel.org To: Andrew Morton Cc: linux-api@vger.kernel.org, linux-mm@kvack.org, LKML , Michal Hocko , Vlastimil Babka List-Id: linux-api@vger.kernel.org From: Michal Hocko David Rientjes has reported that 1860033237d4 ("mm: make PR_SET_THP_DISABLE immediately active") has changed the way how we report THPable VMAs to the userspace. Their monitoring tool is triggering false alarms on PR_SET_THP_DISABLE tasks because it considers an insufficient THP usage as a memory fragmentation resp. memory pressure issue. Before the said commit each newly created VMA inherited VM_NOHUGEPAGE flag and that got exposed to the userspace via /proc//smaps file. This implementation had its downsides as explained in the commit message but it is true that the userspace doesn't have any means to query for the process wide THP enabled/disabled status. PR_SET_THP_DISABLE is a process wide flag so it makes a lot of sense to export in the process wide context rather than per-vma. Introduce a new field to /proc//status which export this status. If PR_SET_THP_DISABLE is used then it reports false same as when the THP is not compiled in. It doesn't consider the global THP status because we already export that information via sysfs Fixes: 1860033237d4 ("mm: make PR_SET_THP_DISABLE immediately active") Acked-by: Vlastimil Babka Signed-off-by: Michal Hocko --- Documentation/filesystems/proc.txt | 3 +++ fs/proc/array.c | 10 ++++++++++ 2 files changed, 13 insertions(+) diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt index cd465304bec4..b24fd9bccc99 100644 --- a/Documentation/filesystems/proc.txt +++ b/Documentation/filesystems/proc.txt @@ -182,6 +182,7 @@ For example, to get the status information of a process, all you have to do is VmSwap: 0 kB HugetlbPages: 0 kB CoreDumping: 0 + THP_enabled: 1 Threads: 1 SigQ: 0/28578 SigPnd: 0000000000000000 @@ -256,6 +257,8 @@ Table 1-2: Contents of the status files (as of 4.8) HugetlbPages size of hugetlb memory portions CoreDumping process's memory is currently being dumped (killing the process may lead to a corrupted core) + THP_enabled process is allowed to use THP (returns 0 when + PR_SET_THP_DISABLE is set on the process Threads number of threads SigQ number of signals queued/max. number for queue SigPnd bitmap of pending signals for the thread diff --git a/fs/proc/array.c b/fs/proc/array.c index 0ceb3b6b37e7..9d428d5a0ac8 100644 --- a/fs/proc/array.c +++ b/fs/proc/array.c @@ -392,6 +392,15 @@ static inline void task_core_dumping(struct seq_file *m, struct mm_struct *mm) seq_putc(m, '\n'); } +static inline void task_thp_status(struct seq_file *m, struct mm_struct *mm) +{ + bool thp_enabled = IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE); + + if (thp_enabled) + thp_enabled = !test_bit(MMF_DISABLE_THP, &mm->flags); + seq_printf(m, "THP_enabled:\t%d\n", thp_enabled); +} + int proc_pid_status(struct seq_file *m, struct pid_namespace *ns, struct pid *pid, struct task_struct *task) { @@ -406,6 +415,7 @@ int proc_pid_status(struct seq_file *m, struct pid_namespace *ns, if (mm) { task_mem(m, mm); task_core_dumping(m, mm); + task_thp_status(m, mm); mmput(mm); } task_sig(m, task); -- 2.19.2