Messages in this thread Patch in this message | | | Date | Mon, 13 Jun 2022 11:18:23 +0530 | Subject | Re: [PATCH v6 03/13] mm/demotion: Return error on write to numa_demotion sysfs | From | Aneesh Kumar K V <> |
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On 6/13/22 11:03 AM, Ying Huang wrote: > On Mon, 2022-06-13 at 09:05 +0530, Aneesh Kumar K V wrote: >> On 6/13/22 8:56 AM, Ying Huang wrote: >>> On Fri, 2022-06-10 at 19:22 +0530, Aneesh Kumar K.V wrote: >>>> With CONFIG_MIGRATION disabled return EINVAL on write. >>>> >>>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> >>>> --- >>>> mm/memory-tiers.c | 3 +++ >>>> 1 file changed, 3 insertions(+) >>>> >>>> diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c >>>> index 9c6b40d7e0bf..c3123a457d90 100644 >>>> --- a/mm/memory-tiers.c >>>> +++ b/mm/memory-tiers.c >>>> @@ -105,6 +105,9 @@ static ssize_t numa_demotion_enabled_store(struct kobject *kobj, >>>> { >>>> ssize_t ret; >>>> >>>> >>>> >>>> + if (!IS_ENABLED(CONFIG_MIGRATION)) >>>> + return -EINVAL; >>>> + >>> >>> How about enclose numa_demotion_enabled_xxx related code with CONFIG_MIGRATION? >>> >> >> IIUC there is a desire to use IS_ENABLED() in the kernel instead of >> #ifdef since that helps in more compile time checks. Because there are >> no dead codes during compile now with IS_ENABLED(). > > IS_ENABLED() is used to reduce usage of "#ifdef" in ".c" file, > especially inside a function. We have good build test coverage with > 0Day now. > > To avoid code size inflate, it's better to use #ifdef CONFIG_MIGRATION. >
For a diff like below I am finding IS_ENABLED better.
size memory-tiers.o.isenabled memory-tiers.o text data bss dec hex filename 4776 989 5 5770 168a memory-tiers.o.isenabled 5257 990 5 6252 186c memory-tiers.o
modified mm/memory-tiers.c @@ -710,12 +710,11 @@ static int __meminit migrate_on_reclaim_callback(struct notifier_block *self,
static void __init migrate_on_reclaim_init(void) { - - if (IS_ENABLED(CONFIG_MIGRATION)) { +#ifdef CONFIG_MIGRATION node_demotion = kcalloc(MAX_NUMNODES, sizeof(struct demotion_nodes), GFP_KERNEL); WARN_ON(!node_demotion); - } +#endif hotplug_memory_notifier(migrate_on_reclaim_callback, 100); }
@@ -844,14 +843,19 @@ static ssize_t numa_demotion_enabled_show(struct kobject *kobj, numa_demotion_enabled ? "true" : "false"); }
+#ifdef CONFIG_MIGRATION static ssize_t numa_demotion_enabled_store(struct kobject *kobj, struct kobj_attribute *attr, const char *buf, size_t count) { - ssize_t ret; - - if (!IS_ENABLED(CONFIG_MIGRATION)) - return -EINVAL; + return -EINVAL; +} +#else +static ssize_t numa_demotion_enabled_store(struct kobject *kobj, + struct kobj_attribute *attr, + const char *buf, size_t count) +{ + ssize_t ret;
ret = kstrtobool(buf, &numa_demotion_enabled); if (ret) @@ -859,6 +863,7 @@ static ssize_t numa_demotion_enabled_store(struct kobject *kobj,
return count; } +#endif
static struct kobj_attribute numa_demotion_enabled_attr = __ATTR(demotion_enabled, 0644, numa_demotion_enabled_show, I also find that #ifdef config not easier to the eyes. If there is a large code that we can end up #ifdef out, then it might be worth it. IIUC, we might want to keep the establish_migration target to find top_tier rank and lower_tier mask. Once we do that only thing that we could comment out is the node_demotion sysfs creation and I was considering to keep that even if migration is disabled with a write to the file returning EINVAL. I could switch that if you strongly feel that we should hide node_demotion sysfs file.
-aneesh
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