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?
Looks like you didn't apply this. Here's proper patch:
>From 8b4b0d0742998042b38d2ba26d4432b26fe71707 Mon Sep 17 00:00:00 2001
From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Date: Thu, 2 Apr 2015 14:56:25 +0300
Subject: [PATCH] thp: cleanup khugepaged startup
Few trivial cleanups:
- no need to call set_recommended_min_free_kbytes() from
late_initcall() -- start_khugepaged() calls it;
- no need to call set_recommended_min_free_kbytes() from
start_khugepaged() if khugepaged is not started;
- there isn't much point in running start_khugepaged() if we've just
set transparent_hugepage_flags to zero;
- start_khugepaged() is misnamed -- it also used to stop the thread;
Not-yet-signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
---
mm/huge_memory.c | 18 ++++++++----------
1 file changed, 8 insertions(+), 10 deletions(-)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 370a3bbc960d..95df717c0095 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -110,10 +110,6 @@ static int set_recommended_min_free_kbytes(void)
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_kbytes(void)
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 kobject *kobj,
int err;
mutex_lock(&khugepaged_mutex);
- err = start_khugepaged();
+ err = start_stop_khugepaged();
mutex_unlock(&khugepaged_mutex);
if (err)
@@ -651,10 +647,12 @@ 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;
+ return 0;
+ }
- err = start_khugepaged();
+ err = start_stop_khugepaged();
if (err)
goto err_khugepaged;
--
Kirill A. Shutemov
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