From: David Hildenbrand <david@redhat.com>
To: xu.xin16@zte.com.cn, akpm@linux-foundation.org
Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
shr@devkernel.io
Subject: Re: [PATCH linux-next v2] ksm: add ksm involvement information for each process
Date: Fri, 26 Apr 2024 10:13:04 +0200 [thread overview]
Message-ID: <bc0e1cdd-2d9d-437c-8fc9-4df0e13c48c0@redhat.com> (raw)
In-Reply-To: <20240426094619962AxIC6CSpfpJNeiy8HRA9h@zte.com.cn>
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/
--
Cheers,
David / dhildenb
next prev parent reply other threads:[~2024-04-26 8:13 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-26 1:46 [PATCH linux-next v2] ksm: add ksm involvement information for each process xu.xin16
2024-04-26 8:13 ` David Hildenbrand [this message]
2024-05-11 8:12 ` xu xin
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