On Tue 01-12-20 16:02:13, Alex Shi wrote: > Pages in pagevec may have different lruvec, so we have to do relock in > function pagevec_lru_move_fn(), but a relock may cause current cpu wait > for long time on the same lock for spinlock fairness reason. > > Before per memcg lru_lock, we have to bear the relock since the spinlock > is the only way to serialize page's memcg/lruvec. Now TestClearPageLRU > could be used to isolate pages exculsively, and stable the page's > lruvec/memcg. So it gives us a chance to sort the page's lruvec before > moving action in pagevec_lru_move_fn. Then we don't suffer from the > spinlock's fairness wait.
Do you have any data to show any improvements from this? > Signed-off-by: Alex Shi <alex....@linux.alibaba.com> > Cc: Konstantin Khlebnikov <koc...@gmail.com> > Cc: Hugh Dickins <hu...@google.com> > Cc: Yu Zhao <yuz...@google.com> > Cc: Michal Hocko <mho...@suse.com> > Cc: Matthew Wilcox (Oracle) <wi...@infradead.org> > Cc: Andrew Morton <a...@linux-foundation.org> > Cc: linux...@kvack.org > Cc: linux-kernel@vger.kernel.org > --- > mm/swap.c | 92 +++++++++++++++++++++++++++++++++++++++++++++++-------- > 1 file changed, 79 insertions(+), 13 deletions(-) > > diff --git a/mm/swap.c b/mm/swap.c > index 490553f3f9ef..17d8990e5ca7 100644 > --- a/mm/swap.c > +++ b/mm/swap.c > @@ -201,29 +201,95 @@ int get_kernel_page(unsigned long start, int write, > struct page **pages) > } > EXPORT_SYMBOL_GPL(get_kernel_page); > > +/* Pratt's gaps for shell sort, https://en.wikipedia.org/wiki/Shellsort */ > +static int gaps[] = { 6, 4, 3, 2, 1, 0}; > + > +/* Shell sort pagevec[] on page's lruvec.*/ > +static void shell_sort(struct pagevec *pvec, unsigned long *lvaddr) > +{ > + int g, i, j, n = pagevec_count(pvec); > + > + for (g=0; gaps[g] > 0 && gaps[g] <= n/2; g++) { > + int gap = gaps[g]; > + > + for (i = gap; i < n; i++) { > + unsigned long tmp = lvaddr[i]; > + struct page *page = pvec->pages[i]; > + > + for (j = i - gap; j >= 0 && lvaddr[j] > tmp; j -= gap) { > + lvaddr[j + gap] = lvaddr[j]; > + pvec->pages[j + gap] = pvec->pages[j]; > + } > + lvaddr[j + gap] = tmp; > + pvec->pages[j + gap] = page; > + } > + } > +} > + > +/* Get lru bit cleared page and their lruvec address, release the others */ > +void sort_isopv(struct pagevec *pvec, struct pagevec *isopv, > + unsigned long *lvaddr) > +{ > + int i, j; > + struct pagevec busypv; > + > + pagevec_init(&busypv); > + > + for (i = 0, j = 0; i < pagevec_count(pvec); i++) { > + struct page *page = pvec->pages[i]; > + > + pvec->pages[i] = NULL; > + > + /* block memcg migration during page moving between lru */ > + if (!TestClearPageLRU(page)) { > + pagevec_add(&busypv, page); > + continue; > + } > + lvaddr[j++] = (unsigned long) > + mem_cgroup_page_lruvec(page, page_pgdat(page)); > + pagevec_add(isopv, page); > + } > + pagevec_reinit(pvec); > + if (pagevec_count(&busypv)) > + release_pages(busypv.pages, busypv.nr); > + > + shell_sort(isopv, lvaddr); > +} > + > static void pagevec_lru_move_fn(struct pagevec *pvec, > void (*move_fn)(struct page *page, struct lruvec *lruvec)) > { > - int i; > + int i, n; > struct lruvec *lruvec = NULL; > unsigned long flags = 0; > + unsigned long lvaddr[PAGEVEC_SIZE]; > + struct pagevec isopv; > > - for (i = 0; i < pagevec_count(pvec); i++) { > - struct page *page = pvec->pages[i]; > + pagevec_init(&isopv); > > - /* block memcg migration during page moving between lru */ > - if (!TestClearPageLRU(page)) > - continue; > + sort_isopv(pvec, &isopv, lvaddr); > > - lruvec = relock_page_lruvec_irqsave(page, lruvec, &flags); > - (*move_fn)(page, lruvec); > + n = pagevec_count(&isopv); > + if (!n) > + return; > > - SetPageLRU(page); > + lruvec = (struct lruvec *)lvaddr[0]; > + spin_lock_irqsave(&lruvec->lru_lock, flags); > + > + for (i = 0; i < n; i++) { > + /* lock new lruvec if lruvec changes, we have sorted them */ > + if (lruvec != (struct lruvec *)lvaddr[i]) { > + spin_unlock_irqrestore(&lruvec->lru_lock, flags); > + lruvec = (struct lruvec *)lvaddr[i]; > + spin_lock_irqsave(&lruvec->lru_lock, flags); > + } > + > + (*move_fn)(isopv.pages[i], lruvec); > + > + SetPageLRU(isopv.pages[i]); > } > - if (lruvec) > - unlock_page_lruvec_irqrestore(lruvec, flags); > - release_pages(pvec->pages, pvec->nr); > - pagevec_reinit(pvec); > + spin_unlock_irqrestore(&lruvec->lru_lock, flags); > + release_pages(isopv.pages, isopv.nr); > } > > static void pagevec_move_tail_fn(struct page *page, struct lruvec *lruvec) > -- > 2.29.GIT > -- Michal Hocko SUSE Labs
