mm, swap: add sysfs interface for VMA based swap readahead (d9bfcfdc) · Commits · 戴 / test

Documentation/ABI/testing/sysfs-kernel-mm-swap

0 → 100644

+26 −0

Original line number	Diff line number	Diff line
		What: /sys/kernel/mm/swap/
		Date: August 2017
		Contact: Linux memory management mailing list <linux-mm@kvack.org>
		Description: Interface for swapping

		What: /sys/kernel/mm/swap/vma_ra_enabled
		Date: August 2017
		Contact: Linux memory management mailing list <linux-mm@kvack.org>
		Description: Enable/disable VMA based swap readahead.

		If set to true, the VMA based swap readahead algorithm
		will be used for swappable anonymous pages mapped in a
		VMA, and the global swap readahead algorithm will be
		still used for tmpfs etc. other users. If set to
		false, the global swap readahead algorithm will be
		used for all swappable pages.

		What: /sys/kernel/mm/swap/vma_ra_max_order
		Date: August 2017
		Contact: Linux memory management mailing list <linux-mm@kvack.org>
		Description: The max readahead size in order for VMA based swap readahead

		VMA based swap readahead algorithm will readahead at
		most 1 << max_order pages for each readahead. The
		real readahead size for each readahead will be scaled
		according to the estimation algorithm.

mm/swap_state.c

+80 −0

Original line number	Diff line number	Diff line
		@@ -751,3 +751,83 @@ skip:
		return read_swap_cache_async(fentry, gfp_mask, vma, vmf->address,
		swap_ra->win == 1);
		}

		#ifdef CONFIG_SYSFS
		static ssize_t vma_ra_enabled_show(struct kobject *kobj,
		struct kobj_attribute attr, char buf)
		{
		return sprintf(buf, "%s\n", swap_vma_readahead ? "true" : "false");
		}
		static ssize_t vma_ra_enabled_store(struct kobject *kobj,
		struct kobj_attribute *attr,
		const char *buf, size_t count)
		{
		if (!strncmp(buf, "true", 4) \|\| !strncmp(buf, "1", 1))
		swap_vma_readahead = true;
		else if (!strncmp(buf, "false", 5) \|\| !strncmp(buf, "0", 1))
		swap_vma_readahead = false;
		else
		return -EINVAL;

		return count;
		}
		static struct kobj_attribute vma_ra_enabled_attr =
		__ATTR(vma_ra_enabled, 0644, vma_ra_enabled_show,
		vma_ra_enabled_store);

		static ssize_t vma_ra_max_order_show(struct kobject *kobj,
		struct kobj_attribute attr, char buf)
		{
		return sprintf(buf, "%d\n", swap_ra_max_order);
		}
		static ssize_t vma_ra_max_order_store(struct kobject *kobj,
		struct kobj_attribute *attr,
		const char *buf, size_t count)
		{
		int err, v;

		err = kstrtoint(buf, 10, &v);
		if (err \|\| v > SWAP_RA_ORDER_CEILING \|\| v <= 0)
		return -EINVAL;

		swap_ra_max_order = v;

		return count;
		}
		static struct kobj_attribute vma_ra_max_order_attr =
		__ATTR(vma_ra_max_order, 0644, vma_ra_max_order_show,
		vma_ra_max_order_store);

		static struct attribute *swap_attrs[] = {
		&vma_ra_enabled_attr.attr,
		&vma_ra_max_order_attr.attr,
		NULL,
		};

		static struct attribute_group swap_attr_group = {
		.attrs = swap_attrs,
		};

		static int __init swap_init_sysfs(void)
		{
		int err;
		struct kobject *swap_kobj;

		swap_kobj = kobject_create_and_add("swap", mm_kobj);
		if (!swap_kobj) {
		pr_err("failed to create swap kobject\n");
		return -ENOMEM;
		}
		err = sysfs_create_group(swap_kobj, &swap_attr_group);
		if (err) {
		pr_err("failed to register swap group\n");
		goto delete_obj;
		}
		return 0;

		delete_obj:
		kobject_put(swap_kobj);
		return err;
		}
		subsys_initcall(swap_init_sysfs);
		#endif

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