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SubjectRe: [PATCH 2/3] mm: replace per-cpu lru-add page-vectors with page-lists
Konstantin Khlebnikov wrote:
> This patch replaces page-vectors with page-lists in lru_cache_add*() functions.
> We can use page->lru for linking because page obviously not in lru.
>
> Now per-cpu batch limited with its pages total size, not pages count,
> otherwise it can be extremely huge if there many huge-pages inside:
> PAGEVEC_SIZE * HPAGE_SIZE = 28Mb, per-cpu!
> These pages are hidden from memory reclaimer for a while.
> New limit: LRU_CACHE_ADD_BATCH = 64 (* PAGE_SIZE = 256Kb)
>
> So, huge-page adding now will always drain per-cpu list. Huge-page allocation
> and preparation is long procedure, thus nobody will notice this draining.
>
> Draining procedure disables preemption only for pages list isolation,
> thus batch size can be increased without negative effect for latency.
>
> Plus this patch introduces new function lru_cache_add_list() and use it in
> mpage_readpages() and read_pages(). There pages already collected in list.
> Unlike to single-page lru-add, list-add reuse page-referencies from caller,
> thus we save one page_get()/page_put() per page.
>
> Signed-off-by: Konstantin Khlebnikov<khlebnikov@openvz.org>
> ---
> fs/mpage.c | 21 +++++++----
> include/linux/swap.h | 2 +
> mm/readahead.c | 15 +++++---
> mm/swap.c | 99 +++++++++++++++++++++++++++++++++++++++++++++-----
> 4 files changed, 114 insertions(+), 23 deletions(-)
>

>
> pvec =&per_cpu(lru_rotate_pvecs, cpu);
> @@ -765,6 +841,11 @@ EXPORT_SYMBOL(pagevec_lookup_tag);
> void __init swap_setup(void)
> {
> unsigned long megs = totalram_pages>> (20 - PAGE_SHIFT);
> + int cpu, lru;
> +
> + for_each_possible_cpu(cpu)
> + for_each_lru(lru)
> + INIT_LIST_HEAD(per_cpu(lru_add_pages, cpu) + lru);

As I afraid, here is is too late for this initialization.
This must be in core-initcall.

I'll send v2 together with update lru-lock splitting rebased to linux-next.

>
> #ifdef CONFIG_SWAP
> bdi_init(swapper_space.backing_dev_info);
>



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