| Message ID | 20240426094619962AxIC6CSpfpJNeiy8HRA9h@zte.com.cn (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [linux-next,v2] ksm: add ksm involvement information for each process | expand |
On 26.04.24 03:46, 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 > MMF_VM_MERGEABLE and MMF_VM_MERGE_ANY. It helps administrators to > better know the system's KSM behavior at process level. > > KSM_mergeable: yes/no > whether the process'mm is added by madvise() into the candidate list > of KSM or not. > 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. > Thinking about it, we should avoid exposing internal toggles with unclear semantics to the user. See below. > Changelog > ========= > v1 -> v2: > replace the internal flag names with straightforward strings. > * MMF_VM_MERGEABLE -> KSM_mergeable > * MMF_VM_MERGE_ANY -> KSM_merge_any > > Signed-off-by: xu xin <xu.xin16@zte.com.cn> > --- > fs/proc/base.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/fs/proc/base.c b/fs/proc/base.c > index 18550c071d71..50e808ffcda4 100644 > --- a/fs/proc/base.c > +++ b/fs/proc/base.c > @@ -3217,6 +3217,10 @@ static int proc_pid_ksm_stat(struct seq_file *m, struct pid_namespace *ns, > seq_printf(m, "ksm_zero_pages %lu\n", mm->ksm_zero_pages); > 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_mergeable: %s\n", > + test_bit(MMF_VM_MERGEABLE, &mm->flags) ? "yes" : "no"); All it *currently* means is "we called __ksm_enter()" once. It does not mean that KSM is still enabled for that process and that any VMA would be considered for merging. I don't think we should expose this. That information can be more reliably had by looking at "/proc/pid/smaps" and looking for "mg". Which tells you exactly if any VMA (and which) is currently applicable to KSM. > + seq_printf(m, "KSM_merge_any: %s\n", > + test_bit(MMF_VM_MERGE_ANY, &mm->flags) ? "yes" : "no"); This makes more sense to export. It's the same as reading prctl(PR_GET_MEMORY_MERGE). The man page [1] calls it simply "KSM has been enabled for this process", so process-wide KSM compared to per-VMA KSM. "KSM_enabled:" *might* be more reasonable in the context of PR_SET_MEMORY_MERGE. It wouldn't tell though if KSM is enabled on the system, though. [1] https://lore.kernel.org/linux-mm/20230227220206.436662-1-shr@devkernel.io/T/
>> @@ -3217,6 +3217,10 @@ static int proc_pid_ksm_stat(struct seq_file *m, struct pid_namespace *ns, >> seq_printf(m, "ksm_zero_pages %lu\n", mm->ksm_zero_pages); >> 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_mergeable: %s\n", >> + test_bit(MMF_VM_MERGEABLE, &mm->flags) ? "yes" : "no"); > >All it *currently* means is "we called __ksm_enter()" once. It does not >mean that KSM is still enabled for that process and that any VMA would >be considered for merging. > >I don't think we should expose this. > >That information can be more reliably had by looking at > >"/proc/pid/smaps" and looking for "mg". > >Which tells you exactly if any VMA (and which) is currently applicable >to KSM. > > >> + seq_printf(m, "KSM_merge_any: %s\n", >> + test_bit(MMF_VM_MERGE_ANY, &mm->flags) ? "yes" : "no"); > >This makes more sense to export. It's the same as reading >prctl(PR_GET_MEMORY_MERGE). > >The man page [1] calls it simply "KSM has been enabled for this >process", so process-wide KSM compared to per-VMA KSM. > >"KSM_enabled:" > >*might* be more reasonable in the context of PR_SET_MEMORY_MERGE. > >It wouldn't tell though if KSM is enabled on the system, though. > I agree it. But I hope admistrators can tell if the process enabled KSM-scan by madvise or prctl. At this point, only "/proc/pid/smaps" is not enough. So can we add a item "KSM_enabled" which has three value as follows? 1) "prctl": KSM has been fully enabled for this process. 2) "madvise": KSM has been enabled on parts of VMA for this process. 3) "never": KSM has been never enabled for this process. Just refer to the semantics of '/sys/kernel/mm/transparent_hugepage/enabled'
diff --git a/fs/proc/base.c b/fs/proc/base.c index 18550c071d71..50e808ffcda4 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -3217,6 +3217,10 @@ static int proc_pid_ksm_stat(struct seq_file *m, struct pid_namespace *ns, seq_printf(m, "ksm_zero_pages %lu\n", mm->ksm_zero_pages); 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_mergeable: %s\n", + test_bit(MMF_VM_MERGEABLE, &mm->flags) ? "yes" : "no"); + seq_printf(m, "KSM_merge_any: %s\n", + test_bit(MMF_VM_MERGE_ANY, &mm->flags) ? "yes" : "no"); mmput(mm); }