From: Huang Ying <ying.huang@xxxxxxxxx> Subject: mm, swap: use page-cluster as max window of VMA based swap readahead When the VMA based swap readahead was introduced, a new knob /sys/kernel/mm/swap/vma_ra_max_order was added as the max window of VMA swap readahead. This is to make it possible to use different max window for VMA based readahead and original physical readahead. But Minchan Kim pointed out that this will cause a regression because setting page-cluster sysctl to zero cannot disable swap readahead with the change. To fix the regression, the page-cluster sysctl is used as the max window of both the VMA based swap readahead and original physical swap readahead. If more fine grained control is needed in the future, more knobs can be added as the subordinate knobs of the page-cluster sysctl. The vma_ra_max_order knob is deleted. Because the knob was introduced in v4.14-rc1, and this patch is targeting being merged before v4.14 releasing, there should be no existing users of this newly added ABI. Link: http://lkml.kernel.org/r/20171011070847.16003-1-ying.huang@xxxxxxxxx Fixes: ec560175c0b6fce ("mm, swap: VMA based swap readahead") Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx> Reported-by: Minchan Kim <minchan@xxxxxxxxxx> Acked-by: Minchan Kim <minchan@xxxxxxxxxx> Acked-by: Michal Hocko <mhocko@xxxxxxxx> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> 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 | 10 --- mm/swap_state.c | 41 ++------------- 2 files changed, 7 insertions(+), 44 deletions(-) diff -puN Documentation/ABI/testing/sysfs-kernel-mm-swap~mm-swap-use-page-cluster-as-max-window-of-vma-based-swap-readahead Documentation/ABI/testing/sysfs-kernel-mm-swap --- a/Documentation/ABI/testing/sysfs-kernel-mm-swap~mm-swap-use-page-cluster-as-max-window-of-vma-based-swap-readahead +++ a/Documentation/ABI/testing/sysfs-kernel-mm-swap @@ -14,13 +14,3 @@ Description: Enable/disable VMA based sw 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-use-page-cluster-as-max-window-of-vma-based-swap-readahead mm/swap_state.c --- a/mm/swap_state.c~mm-swap-use-page-cluster-as-max-window-of-vma-based-swap-readahead +++ a/mm/swap_state.c @@ -39,10 +39,6 @@ struct address_space *swapper_spaces[MAX static unsigned int nr_swapper_spaces[MAX_SWAPFILES]; bool swap_vma_readahead = true; -#define SWAP_RA_MAX_ORDER_DEFAULT 3 - -static int swap_ra_max_order = SWAP_RA_MAX_ORDER_DEFAULT; - #define SWAP_RA_WIN_SHIFT (PAGE_SHIFT / 2) #define SWAP_RA_HITS_MASK ((1UL << SWAP_RA_WIN_SHIFT) - 1) #define SWAP_RA_HITS_MAX SWAP_RA_HITS_MASK @@ -664,6 +660,13 @@ struct page *swap_readahead_detect(struc pte_t *tpte; #endif + max_win = 1 << min_t(unsigned int, READ_ONCE(page_cluster), + SWAP_RA_ORDER_CEILING); + if (max_win == 1) { + swap_ra->win = 1; + return NULL; + } + faddr = vmf->address; entry = pte_to_swp_entry(vmf->orig_pte); if ((unlikely(non_swap_entry(entry)))) @@ -672,12 +675,6 @@ struct page *swap_readahead_detect(struc if (page) return page; - max_win = 1 << READ_ONCE(swap_ra_max_order); - if (max_win == 1) { - swap_ra->win = 1; - return NULL; - } - fpfn = PFN_DOWN(faddr); swap_ra_info = GET_SWAP_RA_VAL(vma); pfn = PFN_DOWN(SWAP_RA_ADDR(swap_ra_info)); @@ -786,32 +783,8 @@ static struct kobj_attribute vma_ra_enab __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, }; _ -- 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
