lkml.org 
[lkml]   [2020]   [Nov]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    From
    SubjectRe: [PATCH next] mm/swap.c: reduce lock contention in lru_cache_add
    On Thu, Nov 26, 2020 at 02:39:03PM +0800, Alex Shi wrote:
    >
    >
    > 在 2020/11/26 下午12:52, Yu Zhao 写道:
    > >> */
    > >> void __pagevec_lru_add(struct pagevec *pvec)
    > >> {
    > >> - int i;
    > >> - struct lruvec *lruvec = NULL;
    > >> + int i, nr_lruvec;
    > >> unsigned long flags = 0;
    > >> + struct page *page;
    > >> + struct lruvecs lruvecs;
    > >>
    > >> - for (i = 0; i < pagevec_count(pvec); i++) {
    > >> - struct page *page = pvec->pages[i];
    > >> + nr_lruvec = sort_page_lruvec(&lruvecs, pvec);
    > > Simply looping pvec multiple times (15 at most) for different lruvecs
    > > would be better because 1) it requires no extra data structures and
    > > therefore has better cache locality (theoretically faster) 2) it only
    > > loops once when !CONFIG_MEMCG and !CONFIG_NUMA and therefore has no
    > > impact on Android and Chrome OS.
    > >
    >
    > With multiple memcgs, it do help a lot, I had gotten 30% grain on readtwice
    > case. but yes, w/o MEMCG and NUMA, it's good to keep old behavior. So
    > would you like has a proposal for this?

    Oh, no, I'm not against your idea. I was saying it doesn't seem
    necessary to sort -- a nested loop would just do the job given
    pagevec is small.

    diff --git a/mm/swap.c b/mm/swap.c
    index cb3794e13b48..1d238edc2907 100644
    --- a/mm/swap.c
    +++ b/mm/swap.c
    @@ -996,15 +996,26 @@ static void __pagevec_lru_add_fn(struct page *page, struct lruvec *lruvec)
    */
    void __pagevec_lru_add(struct pagevec *pvec)
    {
    - int i;
    + int i, j;
    struct lruvec *lruvec = NULL;
    unsigned long flags = 0;

    for (i = 0; i < pagevec_count(pvec); i++) {
    struct page *page = pvec->pages[i];

    + if (!page)
    + continue;
    +
    lruvec = relock_page_lruvec_irqsave(page, lruvec, &flags);
    - __pagevec_lru_add_fn(page, lruvec);
    +
    + for (j = i; j < pagevec_count(pvec); j++) {
    + if (page_to_nid(pvec->pages[j]) != page_to_nid(page) ||
    + page_memcg(pvec->pages[j]) != page_memcg(page))
    + continue;
    +
    + __pagevec_lru_add_fn(pvec->pages[j], lruvec);
    + pvec->pages[j] = NULL;
    + }
    }
    if (lruvec)
    unlock_page_lruvec_irqrestore(lruvec, flags);
    \
     
     \ /
      Last update: 2020-11-26 08:26    [W:2.422 / U:0.216 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site