On Sun, May 08, 2022 at 09:27:10AM +0000, cgel.zte@xxxxxxxxx wrote:
> If ksm_force is set to 0, cancel the feature of ksm_force of this
> process and unmerge those merged pages belonging to VMAs which is not
> madvised as MADV_MERGEABLE of this process, but leave MADV_MERGEABLE
> areas merged.
Is that actually a useful feature? Otherwise, we could simply turn
on/off the existing MMF_VM_MERGEABLE flag instead of introducing this
new bool.
> +Controlling KSM with procfs
> +===========================
> +
> +KSM can also operate on anonymous areas of address space of those processes's
> +knob ``/proc/<pid>/ksm_force`` is on, even if app codes doesn't call madvise()
> +explicitly to advise specific areas as MADV_MERGEABLE.
> +
> +You can set ksm_force to 1 to force all anonymous and qualified VMAs of
> +this process to be involved in KSM scanning. But It is effective only when the
> +klob of ``/sys/kernel/mm/ksm/run`` is set as 1.
I think that last sentence doesn't really add any value.
> + memset(buffer, 0, sizeof(buffer));
> + if (count > sizeof(buffer) - 1)
> + count = sizeof(buffer) - 1;
> + if (copy_from_user(buffer, buf, count)) {
> + err = -EFAULT;
> + goto out_return;
This feels a bit unnecessary. Just 'return -EFAULT' here.
> + }
> +
> + err = kstrtoint(strstrip(buffer), 0, &force);
> +
> + if (err)
> + goto out_return;
'return err'
> + if (force != 0 && force != 1) {
> + err = -EINVAL;
> + goto out_return;
'return -EINVAL'
> + }
> +
> + task = get_proc_task(file_inode(file));
> + if (!task) {
> + err = -ESRCH;
> + goto out_return;
'return -ESRCH'
