Messages in this thread | | | Date | Mon, 03 Aug 2009 19:55:18 +0300 | From | Izik Eidus <> | Subject | Re: [PATCH 5/12] ksm: keep quiet while list empty |
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Hugh Dickins wrote: > ksm_scan_thread already sleeps in wait_event_interruptible until setting > ksm_run activates it; but if there's nothing on its list to look at, i.e. > nobody has yet said madvise MADV_MERGEABLE, it's a shame to be clocking > up system time and full_scans: ksmd_should_run added to check that too. > > And move the mutex_lock out around it: the new counts showed that when > ksm_run is stopped, a little work often got done afterwards, because it > had been read before taking the mutex. > > Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk> > --- > > mm/ksm.c | 28 ++++++++++++++++++++++------ > 1 file changed, 22 insertions(+), 6 deletions(-) > > --- ksm4/mm/ksm.c 2009-08-02 13:49:59.000000000 +0100 > +++ ksm5/mm/ksm.c 2009-08-02 13:50:07.000000000 +0100 > @@ -1287,21 +1287,27 @@ static void ksm_do_scan(unsigned int sca > } > } > > +static int ksmd_should_run(void) > +{ > + return (ksm_run & KSM_RUN_MERGE) && !list_empty(&ksm_mm_head.mm_list); > +} > + > static int ksm_scan_thread(void *nothing) > { > set_user_nice(current, 5); > > while (!kthread_should_stop()) { > - if (ksm_run & KSM_RUN_MERGE) { > - mutex_lock(&ksm_thread_mutex); > + mutex_lock(&ksm_thread_mutex); > + if (ksmd_should_run()) > ksm_do_scan(ksm_thread_pages_to_scan); > - mutex_unlock(&ksm_thread_mutex); > + mutex_unlock(&ksm_thread_mutex); > + > + if (ksmd_should_run()) { > schedule_timeout_interruptible( > msecs_to_jiffies(ksm_thread_sleep_millisecs)); > } else { > wait_event_interruptible(ksm_thread_wait, > - (ksm_run & KSM_RUN_MERGE) || > - kthread_should_stop()); > + ksmd_should_run() || kthread_should_stop()); > } > } > return 0; > @@ -1346,10 +1352,16 @@ int ksm_madvise(struct vm_area_struct *v > > int __ksm_enter(struct mm_struct *mm) > { > - struct mm_slot *mm_slot = alloc_mm_slot(); > + struct mm_slot *mm_slot; > + int needs_wakeup; > + > + mm_slot = alloc_mm_slot(); > if (!mm_slot) > return -ENOMEM; > > + /* Check ksm_run too? Would need tighter locking */ > + needs_wakeup = list_empty(&ksm_mm_head.mm_list); > + > spin_lock(&ksm_mmlist_lock); > insert_to_mm_slots_hash(mm, mm_slot); > /* > @@ -1361,6 +1373,10 @@ int __ksm_enter(struct mm_struct *mm) > spin_unlock(&ksm_mmlist_lock); > > set_bit(MMF_VM_MERGEABLE, &mm->flags); > + > + if (needs_wakeup) > + wake_up_interruptible(&ksm_thread_wait); > + > return 0; > } > > ACK
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