From: Huang Ying <ying.huang@xxxxxxxxx> Subject: mm, swap: add sysfs interface for VMA based swap readahead The sysfs interface to control the VMA based swap readahead is added as follow, /sys/kernel/mm/swap/vma_ra_enabled Enable the VMA based swap readahead algorithm, or use the original global swap readahead algorithm. /sys/kernel/mm/swap/vma_ra_max_order Set the max order of the readahead window size for the VMA based swap readahead algorithm. The corresponding ABI documentation is added too. Link: http://lkml.kernel.org/r/20170807054038.1843-5-ying.huang@xxxxxxxxx Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: Minchan Kim <minchan@xxxxxxxxxx> Cc: Rik van Riel <riel@xxxxxxxxxx> Cc: Shaohua Li <shli@xxxxxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: Fengguang Wu <fengguang.wu@xxxxxxxxx> Cc: Tim Chen <tim.c.chen@xxxxxxxxx> Cc: Dave Hansen <dave.hansen@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- Documentation/ABI/testing/sysfs-kernel-mm-swap | 26 ++++ mm/swap_state.c | 80 +++++++++++++++ 2 files changed, 106 insertions(+) diff -puN /dev/null Documentation/ABI/testing/sysfs-kernel-mm-swap --- /dev/null +++ a/Documentation/ABI/testing/sysfs-kernel-mm-swap @@ -0,0 +1,26 @@ +What: /sys/kernel/mm/swap/ +Date: August 2017 +Contact: Linux memory management mailing list <linux-mm@xxxxxxxxx> +Description: Interface for swapping + +What: /sys/kernel/mm/swap/vma_ra_enabled +Date: August 2017 +Contact: Linux memory management mailing list <linux-mm@xxxxxxxxx> +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@xxxxxxxxx> +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. diff -puN mm/swap_state.c~mm-swap-add-sysfs-interface-for-vma-based-swap-readahead mm/swap_state.c --- a/mm/swap_state.c~mm-swap-add-sysfs-interface-for-vma-based-swap-readahead +++ a/mm/swap_state.c @@ -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 _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
