| Message ID | 20241203192633836RVHhkoK1Amnqjt84D4Ryd@zte.com.cn (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [linux-next,v4] ksm: add ksm involvement information for each process | expand |
On Tue, 3 Dec 2024 19:26:33 +0800 (CST) <xu.xin16@zte.com.cn> wrote: > From: xu xin <xu.xin16@zte.com.cn> > > In /proc/<pid>/ksm_stat, Add two extra ksm involvement items including > KSM_mergeable and KSM_merge_any. It helps administrators to > better know the system's KSM behavior at process level. It's hard for me to judge the usefulness of this. Please tell us more: usage examples, what actions have been taken using this information, etc. > KSM_mergeable: yes/no > whether any VMAs of the process'mm are currently applicable to KSM. Could we simply display VM_MERGEABLE in /proc/<pid>/maps? > KSM_merge_any: yes/no > whether the process'mm is added by prctl() into the candidate list > of KSM or not, and fully enabled at process level. > > ... > > fs/proc/base.c | 11 +++++++++++ > include/linux/ksm.h | 1 + > mm/ksm.c | 19 +++++++++++++++++++ Documentation/admin-guide/mm/ksm.rst will require an update please. > > ... > > --- a/fs/proc/base.c > +++ b/fs/proc/base.c > @@ -3269,6 +3269,7 @@ static int proc_pid_ksm_stat(struct seq_file *m, struct pid_namespace *ns, > struct pid *pid, struct task_struct *task) > { > struct mm_struct *mm; > + int ret = 0; > > mm = get_task_mm(task); > if (mm) { > @@ -3276,6 +3277,16 @@ static int proc_pid_ksm_stat(struct seq_file *m, struct pid_namespace *ns, > seq_printf(m, "ksm_zero_pages %ld\n", mm_ksm_zero_pages(mm)); > seq_printf(m, "ksm_merging_pages %lu\n", mm->ksm_merging_pages); > seq_printf(m, "ksm_process_profit %ld\n", ksm_process_profit(mm)); > + seq_printf(m, "ksm_merge_any: %s\n", > + test_bit(MMF_VM_MERGE_ANY, &mm->flags) ? "yes" : "no"); > + ret = mmap_read_lock_killable(mm); Could do the locking in ksm_process_mergeable()? > + if (ret) { > + mmput(mm); > + return ret; > + } > + seq_printf(m, "ksm_mergeable: %s\n", > + ksm_process_mergeable(mm) ? "yes" : "no"); Calling seq_printf() after the mmap_read_unlock() would be a little more scalable. > + mmap_read_unlock(mm); > mmput(mm); > } > > ... > > --- a/mm/ksm.c > +++ b/mm/ksm.c > @@ -3263,6 +3263,25 @@ static void wait_while_offlining(void) > #endif /* CONFIG_MEMORY_HOTREMOVE */ > > #ifdef CONFIG_PROC_FS > +/* > + * The process is mergeable only if any VMA (and which) is currently > + * applicable to KSM. That sentence needs revisiting, please. > + * The mmap lock must be held in read mode. > + */ > +bool ksm_process_mergeable(struct mm_struct *mm) > +{ > + struct vm_area_struct *vma; > + > + mmap_assert_locked(mm); > + VMA_ITERATOR(vmi, mm, 0); > + for_each_vma(vmi, vma) > + if (vma->vm_flags & VM_MERGEABLE) > + return true; > + > + return false; > +}
On 04.12.24 01:56, Andrew Morton wrote: > On Tue, 3 Dec 2024 19:26:33 +0800 (CST) <xu.xin16@zte.com.cn> wrote: > >> From: xu xin <xu.xin16@zte.com.cn> >> >> In /proc/<pid>/ksm_stat, Add two extra ksm involvement items including >> KSM_mergeable and KSM_merge_any. It helps administrators to >> better know the system's KSM behavior at process level. > > It's hard for me to judge the usefulness of this. Please tell us more: > usage examples, what actions have been taken using this information, etc. Seconded. > >> KSM_mergeable: yes/no >> whether any VMAs of the process'mm are currently applicable to KSM. > > Could we simply display VM_MERGEABLE in /proc/<pid>/maps? We indicate in /proc/<pid>/smaps "mg" for VM_MERGEABLE already. The "nasty" thing about smaps is that it does all the page table walking to gather memory statistics, which can be rather expensive. I was recently asking myself whether we should have a "cheaper" way to obtain such details about mappings. /proc/<pid>/maps is likely impossible to extend (similarly display flags) I suspect.
diff --git a/fs/proc/base.c b/fs/proc/base.c index 0edf14a9840e..a50b222a5917 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -3269,6 +3269,7 @@ static int proc_pid_ksm_stat(struct seq_file *m, struct pid_namespace *ns, struct pid *pid, struct task_struct *task) { struct mm_struct *mm; + int ret = 0; mm = get_task_mm(task); if (mm) { @@ -3276,6 +3277,16 @@ static int proc_pid_ksm_stat(struct seq_file *m, struct pid_namespace *ns, seq_printf(m, "ksm_zero_pages %ld\n", mm_ksm_zero_pages(mm)); seq_printf(m, "ksm_merging_pages %lu\n", mm->ksm_merging_pages); seq_printf(m, "ksm_process_profit %ld\n", ksm_process_profit(mm)); + seq_printf(m, "ksm_merge_any: %s\n", + test_bit(MMF_VM_MERGE_ANY, &mm->flags) ? "yes" : "no"); + ret = mmap_read_lock_killable(mm); + if (ret) { + mmput(mm); + return ret; + } + seq_printf(m, "ksm_mergeable: %s\n", + ksm_process_mergeable(mm) ? "yes" : "no"); + mmap_read_unlock(mm); mmput(mm); } diff --git a/include/linux/ksm.h b/include/linux/ksm.h index 6a53ac4885bb..d73095b5cd96 100644 --- a/include/linux/ksm.h +++ b/include/linux/ksm.h @@ -93,6 +93,7 @@ void folio_migrate_ksm(struct folio *newfolio, struct folio *folio); void collect_procs_ksm(const struct folio *folio, const struct page *page, struct list_head *to_kill, int force_early); long ksm_process_profit(struct mm_struct *); +bool ksm_process_mergeable(struct mm_struct *mm); #else /* !CONFIG_KSM */ diff --git a/mm/ksm.c b/mm/ksm.c index 7ac59cde626c..e87af149d5ee 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -3263,6 +3263,25 @@ static void wait_while_offlining(void) #endif /* CONFIG_MEMORY_HOTREMOVE */ #ifdef CONFIG_PROC_FS +/* + * The process is mergeable only if any VMA (and which) is currently + * applicable to KSM. + * + * The mmap lock must be held in read mode. + */ +bool ksm_process_mergeable(struct mm_struct *mm) +{ + struct vm_area_struct *vma; + + mmap_assert_locked(mm); + VMA_ITERATOR(vmi, mm, 0); + for_each_vma(vmi, vma) + if (vma->vm_flags & VM_MERGEABLE) + return true; + + return false; +} + long ksm_process_profit(struct mm_struct *mm) { return (long)(mm->ksm_merging_pages + mm_ksm_zero_pages(mm)) * PAGE_SIZE -