Re: [PATCH RFC v2 3/4] mm/ksm: introduce force_madvise knob

Timofey Titovets
2019-05-15T00:49:29Z

LGTM

Reviewed-by: Timofey Titovets <nefelim4ag@gmail.com>

вт, 14 мая 2019 г. в 16:22, Aaron Tomlin <atomlin@redhat.com>:
>
> On Tue 2019-05-14 15:16 +0200, Oleksandr Natalenko wrote:
> > Present a new sysfs knob to mark task's anonymous memory as mergeable.
> >
> > To force merging task's VMAs, its PID is echoed in a write-only file:
> >
> > # echo PID > /sys/kernel/mm/ksm/force_madvise
> >
> > Force unmerging is done similarly, but with "minus" sign:
> >
> > # echo -PID > /sys/kernel/mm/ksm/force_madvise
> >
> > "0" or "-0" can be used to control the current task.
> >
> > To achieve this, previously introduced ksm_enter()/ksm_leave() helpers
> > are used in the "store" handler.
> >
> > Signed-off-by: Oleksandr Natalenko <oleksandr@redhat.com>
> > ---
> > mm/ksm.c | 68 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> > 1 file changed, 68 insertions(+)
> >
> > diff --git a/mm/ksm.c b/mm/ksm.c
> > index e9f3901168bb..22c59fb03d3a 100644
> > --- a/mm/ksm.c
> > +++ b/mm/ksm.c
> > @@ -2879,10 +2879,77 @@ static void wait_while_offlining(void)
> >
> > #define KSM_ATTR_RO(_name) \
> > static struct kobj_attribute _name##_attr = __ATTR_RO(_name)
> > +#define KSM_ATTR_WO(_name) \
> > + static struct kobj_attribute _name##_attr = __ATTR_WO(_name)
> > #define KSM_ATTR(_name) \
> > static struct kobj_attribute _name##_attr = \
> > __ATTR(_name, 0644, _name##_show, _name##_store)
> >
> > +static ssize_t force_madvise_store(struct kobject *kobj,
> > + struct kobj_attribute *attr,
> > + const char *buf, size_t count)
> > +{
> > + int err;
> > + pid_t pid;
> > + bool merge = true;
> > + struct task_struct *tsk;
> > + struct mm_struct *mm;
> > + struct vm_area_struct *vma;
> > +
> > + err = kstrtoint(buf, 10, &pid);
> > + if (err)
> > + return -EINVAL;
> > +
> > + if (pid < 0) {
> > + pid = abs(pid);
> > + merge = false;
> > + }
> > +
> > + if (!pid && *buf == '-')
> > + merge = false;
> > +
> > + rcu_read_lock();
> > + if (pid) {
> > + tsk = find_task_by_vpid(pid);
> > + if (!tsk) {
> > + err = -ESRCH;
> > + rcu_read_unlock();
> > + goto out;
> > + }
> > + } else {
> > + tsk = current;
> > + }
> > +
> > + tsk = tsk->group_leader;
> > +
> > + get_task_struct(tsk);
> > + rcu_read_unlock();
> > +
> > + mm = get_task_mm(tsk);
> > + if (!mm) {
> > + err = -EINVAL;
> > + goto out_put_task_struct;
> > + }
> > + down_write(&mm->mmap_sem);
> > + vma = mm->mmap;
> > + while (vma) {
> > + if (merge)
> > + ksm_enter(vma->vm_mm, vma, &vma->vm_flags);
> > + else
> > + ksm_leave(vma, vma->vm_start, vma->vm_end, &vma->vm_flags);
> > + vma = vma->vm_next;
> > + }
> > + up_write(&mm->mmap_sem);
> > + mmput(mm);
> > +
> > +out_put_task_struct:
> > + put_task_struct(tsk);
> > +
> > +out:
> > + return err ? err : count;
> > +}
> > +KSM_ATTR_WO(force_madvise);
> > +
> > static ssize_t sleep_millisecs_show(struct kobject *kobj,
> > struct kobj_attribute *attr, char *buf)
> > {
> > @@ -3185,6 +3252,7 @@ static ssize_t full_scans_show(struct kobject *kobj,
> > KSM_ATTR_RO(full_scans);
> >
> > static struct attribute *ksm_attrs[] = {
> > + &force_madvise_attr.attr,
> > &sleep_millisecs_attr.attr,
> > &pages_to_scan_attr.attr,
> > &run_attr.attr,
>
> Looks fine to me.
>
> Reviewed-by: Aaron Tomlin <atomlin@redhat.com>
>
> --
> Aaron Tomlin

--
Have a nice day,
Timofey.