linux-kernel - Re: [PATCH 1/3] staging: lowmemorykiller: change lowmem_adj to lowmem_score

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Date:	Wed, 22 Jun 2016 11:10:57 +0800
From:	Ganesh Mahendran <opensource.ganesh@...il.com>
To:	David Rientjes <rientjes@...gle.com>
Cc:	devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
	gregkh@...uxfoundation.org, arve@...roid.com, riandrews@...roid.com
Subject: Re: [PATCH 1/3] staging: lowmemorykiller: change lowmem_adj to
 lowmem_score_adj

Hi, David:

On Tue, Jun 21, 2016 at 01:27:40PM -0700, David Rientjes wrote:
> On Tue, 21 Jun 2016, Ganesh Mahendran wrote:
> 
> > om_adj is deprecated, and in lowmemorykiller module, we use score adj
> > to do the comparing.
> > ---
> >                 oom_score_adj = p->signal->oom_score_adj;
> >                 if (oom_score_adj < min_score_adj) {
> >                         task_unlock(p);
> >                         continue;
> >                 }
> > ---
> > 
> > This patch makes the variable name consistent with the usage.
> > 
> 
> Umm, I don't think you can just remove a parameter to a module and replace 
> it with something that has a different unit and not think that userspace 
> will break as a result.

You are right, this change will break android AMS which will set the LMK
watermark via /sys/module/lowmemorykiller/parameters/adj.

Please help to review below change. Only make the varialbe name consistent
with the variable usage.

------
>From 394872fc1993a04ae471b10d7f971d4544812ec4 Mon Sep 17 00:00:00 2001
From: Ganesh Mahendran <opensource.ganesh@...il.com>
Date: Wed, 22 Jun 2016 10:53:13 +0800
Subject: [PATCH v2] staging: lowmemorykiller: make variable name consistent with
 the varialbe usage

LMK use oom_score_adj to do the comparing. But the variable name is
*_adj. This patch makes thevarialbe name consistent with the varialb
usage to avoid ambiguity.

*_adj -> *_score_adj

Signed-off-by: Ganesh Mahendran <opensource.ganesh@...il.com>
---
v2:
  do not change user API - David
---
 drivers/staging/android/lowmemorykiller.c | 23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/drivers/staging/android/lowmemorykiller.c b/drivers/staging/android/lowmemorykiller.c
index 24d2745..6568bbf 100644
--- a/drivers/staging/android/lowmemorykiller.c
+++ b/drivers/staging/android/lowmemorykiller.c
@@ -44,14 +44,15 @@
 #include <linux/notifier.h>
 
 static u32 lowmem_debug_level = 1;
-static short lowmem_adj[6] = {
+
+static short lowmem_score_adj[6] = {
 	0,
-	1,
-	6,
-	12,
+	58,
+	352,
+	705,
 };
 
-static int lowmem_adj_size = 4;
+static int lowmem_score_adj_size = 4;
 static int lowmem_minfree[6] = {
 	3 * 512,	/* 6MB */
 	2 * 1024,	/* 8MB */
@@ -89,20 +90,20 @@ static unsigned long lowmem_scan(struct shrinker *s, struct shrink_control *sc)
 	int minfree = 0;
 	int selected_tasksize = 0;
 	short selected_oom_score_adj;
-	int array_size = ARRAY_SIZE(lowmem_adj);
+	int array_size = ARRAY_SIZE(lowmem_score_adj);
 	int other_free = global_page_state(NR_FREE_PAGES) - totalreserve_pages;
 	int other_file = global_page_state(NR_FILE_PAGES) -
 						global_page_state(NR_SHMEM) -
 						total_swapcache_pages();
 
-	if (lowmem_adj_size < array_size)
-		array_size = lowmem_adj_size;
+	if (lowmem_score_adj_size < array_size)
+		array_size = lowmem_score_adj_size;
 	if (lowmem_minfree_size < array_size)
 		array_size = lowmem_minfree_size;
 	for (i = 0; i < array_size; i++) {
 		minfree = lowmem_minfree[i];
 		if (other_free < minfree && other_file < minfree) {
-			min_score_adj = lowmem_adj[i];
+			min_score_adj = lowmem_score_adj[i];
 			break;
 		}
 	}
@@ -165,7 +166,7 @@ static unsigned long lowmem_scan(struct shrinker *s, struct shrink_control *sc)
 		if (selected->mm)
 			task_set_lmk_waiting(selected);
 		task_unlock(selected);
-		lowmem_print(1, "Killing '%s' (%d), adj %hd,\n"
+		lowmem_print(1, "Killing '%s' (%d), score adj %hd,\n"
 				 "   to free %ldkB on behalf of '%s' (%d) because\n"
 				 "   cache %ldkB is below limit %ldkB for oom_score_adj %hd\n"
 				 "   Free memory is %ldkB above reserved\n",
@@ -205,7 +206,7 @@ device_initcall(lowmem_init);
  * bootargs behaviour is to continue using module_param here.
  */
 module_param_named(cost, lowmem_shrinker.seeks, int, S_IRUGO | S_IWUSR);
-module_param_array_named(adj, lowmem_adj, short, &lowmem_adj_size,
+module_param_array_named(adj, lowmem_score_adj, short, &lowmem_score_adj_size,
 			 S_IRUGO | S_IWUSR);
 module_param_array_named(minfree, lowmem_minfree, uint, &lowmem_minfree_size,
 			 S_IRUGO | S_IWUSR);
-- 
1.9.1