Re: [PATCH v5] mm: cma: support sysfs

Dmitry Osipenko
2021-03-23T21:19:07Z

23.03.2021 22:50, Minchan Kim пишет:
> Since CMA is getting used more widely, it's more important to
> keep monitoring CMA statistics for system health since it's
> directly related to user experience.
>
> This patch introduces sysfs statistics for CMA, in order to provide
> some basic monitoring of the CMA allocator.
>
> * the number of CMA page successful allocations
> * the number of CMA page allocation failures
>
> These two values allow the user to calcuate the allocation

typo: calculate

> struct cma {
> unsigned long base_pfn;
> @@ -16,6 +22,14 @@ struct cma {
> struct debugfs_u32_array dfs_bitmap;
> #endif
> char name[CMA_MAX_NAME];
> +#ifdef CONFIG_CMA_SYSFS
> + /* the number of CMA page successful allocations */
> + atomic64_t nr_pages_succeeded;
> + /* the number of CMA page allocation failures */
> + atomic64_t nr_pages_failed;
> + /* kobject requires dynamic objecjt */

typo: object
...
> +static void cma_kobj_release(struct kobject *kobj)
> +{
> + struct cma_kobject *cma_kobj =
> + container_of(kobj, struct cma_kobject, kobj);

I'd add a to_cma_kobject() helper to improve readability.

> + struct cma *cma = cma_kobj->cma;
> +
> + kfree(cma_kobj);
> + cma->kobj = NULL;
> +}
> +
> +static struct attribute *cma_attrs[] = {
> + &alloc_pages_success_attr.attr,
> + &alloc_pages_fail_attr.attr,
> + NULL,
> +};
> +ATTRIBUTE_GROUPS(cma);
> +
> +static struct kobject *cma_kobj_root;
> +
> +static struct kobj_type cma_ktype = {
> + .release = cma_kobj_release,
> + .sysfs_ops = &kobj_sysfs_ops,
> + .default_groups = cma_groups
> +};
> +
> +static int __init cma_sysfs_init(void)
> +{
> + int i = 0;

unsigned int, for consistency

There is no need to initialize this variable.

> + struct cma *cma;
> +
> + cma_kobj_root = kobject_create_and_add("cma", mm_kobj);
> + if (!cma_kobj_root)
> + return -ENOMEM;
> +
> + for (i = 0; i < cma_area_count; i++) {
> + struct cma_kobject *kobj;
> +
> + cma = &cma_areas[i];
> + kobj = kzalloc(sizeof(struct cma_kobject), GFP_KERNEL);

Checkpatch should warn that kzalloc(*kobj, ..) is a better variant.

I'd also rename kobj to cma_kobj everywhere, for clarity.

> + if (!kobj)
> + goto out;
> +
> + kobj->cma = cma;
> + cma->kobj = kobj;
> + if (kobject_init_and_add(&cma->kobj->kobj, &cma_ktype,
> + cma_kobj_root, "%s", cma->name)) {
> + kobject_put(&cma->kobj->kobj);
> + goto out;
> + }
> + }
> +
> + return 0;
> +out:
> + kobject_put(cma_kobj_root);
> +
> + return -ENOMEM;

kobject_init_and_add returns a error code, it could be different from
ENOMEM. Won't hurt to propagate the proper error code.