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Message-ID: <bc0d16a6-e340-e261-82a0-e17bd236c2d9@linux.alibaba.com>
Date: Thu, 4 Aug 2022 16:04:17 +0800
From: haoxin <xhao@...ux.alibaba.com>
To: David Hildenbrand <david@...hat.com>, willy@...radead.org
Cc: akpm@...ux-foundation.org, adobriyan@...il.com,
keescook@...omium.org, linux-kernel@...r.kernel.org,
linux-mm@...ck.org
Subject: Re: [RFC PATCH V4 1/1] mm: add last level page table numa info to
/proc/pid/numa_pgtable
在 2022/8/1 下午9:28, David Hildenbrand 写道:
> On 01.08.22 14:17, Xin Hao wrote:
>> In many data center servers, the shared memory architectures is
>> Non-Uniform Memory Access (NUMA), remote numa node data access
>> often brings a high latency problem, but what we are easy to ignore
>> is that the page table remote numa access, It can also leads to a
>> performance degradation.
> Let me try rewriting:
>
> "
> Many data center servers employ Non-Uniform Memory Access (NUMA)
> architectures. Remote numa memory access results in high latency. While
> memory placement is one issue, sub-optimal page table placement can also
> result in surprise performance degradation.
> "
Thanks, it reads more clearly.
>> So there add a new interface in /proc, This will help developers to
>> get more info about performance issues if they are caused by cross-NUMA.
>
> Why do we only care about "last level page table", why not about the others?
>
> IMHO, we could emit something like "0, 1, 3, 0" instead for a given user
> space address, showing the NUMA node the page table belongs to from
> highest to lowest page table level.
I have planned to implement the PTE page table in this version first,
and then support other page tables in the next patch later.
>
>> Reported-by: kernel test robot <lkp@...el.com>
> The kernel test robot reported that we need "/proc/pid/numa_pgtable" ?! :)
>
> Just drop that unless it's a follow-up fix.
Get it.
>
>> Signed-off-by: Xin Hao <xhao@...ux.alibaba.com>
>> ---
>> fs/proc/base.c | 2 ++
>> fs/proc/internal.h | 1 +
>> fs/proc/task_mmu.c | 87 ++++++++++++++++++++++++++++++++++++++++++++++
>> 3 files changed, 90 insertions(+)
>>
>> diff --git a/fs/proc/base.c b/fs/proc/base.c
>> index 8dfa36a99c74..487e82dd3275 100644
>> --- a/fs/proc/base.c
>> +++ b/fs/proc/base.c
>> @@ -3224,6 +3224,7 @@ static const struct pid_entry tgid_base_stuff[] = {
>> REG("maps", S_IRUGO, proc_pid_maps_operations),
>> #ifdef CONFIG_NUMA
>> REG("numa_maps", S_IRUGO, proc_pid_numa_maps_operations),
>> + REG("numa_pgtable", S_IRUGO, proc_pid_numa_pgtable_operations),
>> #endif
>> REG("mem", S_IRUSR|S_IWUSR, proc_mem_operations),
>> LNK("cwd", proc_cwd_link),
>> @@ -3571,6 +3572,7 @@ static const struct pid_entry tid_base_stuff[] = {
>> #endif
>> #ifdef CONFIG_NUMA
>> REG("numa_maps", S_IRUGO, proc_pid_numa_maps_operations),
>> + REG("numa_pgtable", S_IRUGO, proc_pid_numa_pgtable_operations),
>> #endif
>> REG("mem", S_IRUSR|S_IWUSR, proc_mem_operations),
>> LNK("cwd", proc_cwd_link),
>> diff --git a/fs/proc/internal.h b/fs/proc/internal.h
>> index 06a80f78433d..e7ed9ef097b6 100644
>> --- a/fs/proc/internal.h
>> +++ b/fs/proc/internal.h
>> @@ -296,6 +296,7 @@ struct mm_struct *proc_mem_open(struct inode *inode, unsigned int mode);
>>
>> extern const struct file_operations proc_pid_maps_operations;
>> extern const struct file_operations proc_pid_numa_maps_operations;
>> +extern const struct file_operations proc_pid_numa_pgtable_operations;
>> extern const struct file_operations proc_pid_smaps_operations;
>> extern const struct file_operations proc_pid_smaps_rollup_operations;
>> extern const struct file_operations proc_clear_refs_operations;
>> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
>> index 2d04e3470d4c..77b7a49757f5 100644
>> --- a/fs/proc/task_mmu.c
>> +++ b/fs/proc/task_mmu.c
>> @@ -1999,4 +1999,91 @@ const struct file_operations proc_pid_numa_maps_operations = {
>> .release = proc_map_release,
>> };
>>
>> +struct pgtable_numa_private {
>> + struct proc_maps_private proc_maps;
>> + unsigned long node[MAX_NUMNODES];
>> +};
>> +
>> +static int gather_pgtable_numa_stats(pmd_t *pmd, unsigned long addr,
>> + unsigned long end, struct mm_walk *walk)
>> +{
>> + struct pgtable_numa_private *priv = walk->private;
>> + struct page *page;
>> + int nid;
>> +
>> + if (pmd_huge(*pmd)) {
>> + page = virt_to_page(pmd);
>> + } else {
>> + page = pmd_page(*pmd);
>> + }
>> +
>> + nid = page_to_nid(page);
>> + priv->node[nid]++;
>> +
>> + return 0;
>> +}
>> +
>> +static const struct mm_walk_ops show_numa_pgtable_ops = {
>> + .pmd_entry = gather_pgtable_numa_stats,
>> +};
>> +
>> +/*
>> + * Display the page talbe allocated per node via /proc.
> s/talbe/table/
>
> but the comment somehow doesn't make sense. We don't display a page table.
>
>> + */
>> +static int show_numa_pgtable(struct seq_file *m, void *v)
>> +{
>> + struct pgtable_numa_private *numa_priv = m->private;
>> + struct vm_area_struct *vma = v;
>> + struct mm_struct *mm = vma->vm_mm;
>> + struct file *file = vma->vm_file;
>> + int nid;
>> +
>> + if (!mm)
>> + return 0;
>> +
>> + memset(numa_priv->node, 0, sizeof(numa_priv->node));
>> +
>> + seq_printf(m, "%08lx ", vma->vm_start);
>> +
>> + if (file) {
>> + seq_puts(m, " file=");
>> + seq_file_path(m, file, "\n\t= ");
>> + } else if (vma->vm_start <= mm->brk && vma->vm_end >= mm->start_brk) {
>> + seq_puts(m, " heap");
>> + } else if (is_stack(vma)) {
>> + seq_puts(m, " stack");
>> + }
>> +
>> + /* mmap_lock is held by m_start */
>> + walk_page_vma(vma, &show_numa_pgtable_ops, numa_priv);
>> +
>> + for_each_node_state(nid, N_MEMORY) {
>> + if (numa_priv->node[nid])
>> + seq_printf(m, " N%d=%lu", nid, numa_priv->node[nid]);
>> + }
>> + seq_putc(m, '\n');
>> +
>> + return 0;
>> +}
>> +
>> +static const struct seq_operations proc_pid_numa_pgtable_op = {
>> + .start = m_start,
>> + .next = m_next,
>> + .stop = m_stop,
>> + .show = show_numa_pgtable,
>> +};
>> +
>> +static int pid_numa_pgtable_open(struct inode *inode, struct file *file)
>> +{
>> + return proc_maps_open(inode, file, &proc_pid_numa_pgtable_op,
>> + sizeof(struct pgtable_numa_private));
>> +}
>> +
>> +const struct file_operations proc_pid_numa_pgtable_operations = {
>> + .open = pid_numa_pgtable_open,
>> + .read = seq_read,
>> + .llseek = seq_lseek,
>> + .release = proc_map_release,
>> +};
>> +
>> #endif /* CONFIG_NUMA */
>> --
>> 2.31.0
>>
>
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