On Fri, Mar 27, 2015 at 03:00:26PM -0700, Andrew Morton wrote:
> On Fri, 27 Mar 2015 14:47:08 -0700 Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> > Fair enough, but take a look at start_khugepaged():
> >
> > : static int start_khugepaged(void)
> > : {
> > : int err = 0;
> > : if (khugepaged_enabled()) {
> > : if (!khugepaged_thread)
> > : khugepaged_thread = kthread_run(khugepaged, NULL,
> > : "khugepaged");
> > : if (unlikely(IS_ERR(khugepaged_thread))) {
> > : pr_err("khugepaged: kthread_run(khugepaged) failed\n");
> > : err = PTR_ERR(khugepaged_thread);
> > : khugepaged_thread = NULL;
> >
> > -->> stop here
> >
> > : }
> > :
> > : if (!list_empty(&khugepaged_scan.mm_head))
> > : wake_up_interruptible(&khugepaged_wait);
> > :
> > : set_recommended_min_free_kbytes();
> > : } else if (khugepaged_thread) {
> > : kthread_stop(khugepaged_thread);
> > : khugepaged_thread = NULL;
> > : }
> > :
> > : return err;
> > : }
>
> Looking more closely... This code seems a bit screwy.
>
> - why is set_recommended_min_free_kbytes() a late_initcall? We've
> already done that within
> subsys_initcall->hugepage_init->set_recommended_min_free_kbytes()
>
> - there isn't much point in running start_khugepaged() if we've just
> set transparent_hugepage_flags to zero.
>
> - start_khugepaged() is misnamed.
>
> So something like this?
Yeah, looks good to me.
> --- a/mm/huge_memory.c~a
> +++ a/mm/huge_memory.c
> @@ -110,10 +110,6 @@ static int set_recommended_min_free_kbyt
> int nr_zones = 0;
> unsigned long recommended_min;
>
> - /* khugepaged thread has stopped to failed to start */
> - if (!khugepaged_thread)
> - return 0;
> -
> for_each_populated_zone(zone)
> nr_zones++;
>
> @@ -145,9 +141,8 @@ static int set_recommended_min_free_kbyt
> setup_per_zone_wmarks();
> return 0;
> }
> -late_initcall(set_recommended_min_free_kbytes);
>
> -static int start_khugepaged(void)
> +static int start_stop_khugepaged(void)
> {
> int err = 0;
> if (khugepaged_enabled()) {
> @@ -158,6 +153,7 @@ static int start_khugepaged(void)
> pr_err("khugepaged: kthread_run(khugepaged) failed\n");
> err = PTR_ERR(khugepaged_thread);
> khugepaged_thread = NULL;
> + goto fail;
> }
>
> if (!list_empty(&khugepaged_scan.mm_head))
> @@ -168,7 +164,7 @@ static int start_khugepaged(void)
> kthread_stop(khugepaged_thread);
> khugepaged_thread = NULL;
> }
> -
> +fail:
> return err;
> }
>
> @@ -302,7 +298,7 @@ static ssize_t enabled_store(struct kobj
> int err;
>
> mutex_lock(&khugepaged_mutex);
> - err = start_khugepaged();
> + err = start_stop_khugepaged();
> mutex_unlock(&khugepaged_mutex);
>
> if (err)
> @@ -651,12 +647,13 @@ static int __init hugepage_init(void)
> * where the extra memory used could hurt more than TLB overhead
> * is likely to save. The admin can still enable it through /sys.
> */
> - if (totalram_pages < (512 << (20 - PAGE_SHIFT)))
> + if (totalram_pages < (512 << (20 - PAGE_SHIFT))) {
> transparent_hugepage_flags = 0;
> -
> - err = start_khugepaged();
> - if (err)
> - goto err_khugepaged;
> + } else {
> + err = start_stop_khugepaged();
> + if (err)
> + goto err_khugepaged;
> + }
>
> return 0;
> err_khugepaged:
> _
>
> --
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--
Kirill A. Shutemov
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