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Date:   Wed,  6 May 2020 17:42:09 -0700
From:   Anthony Yznaga <anthony.yznaga@...cle.com>
To:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc:     willy@...radead.org, corbet@....net, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, x86@...nel.org, hpa@...or.com,
        dave.hansen@...ux.intel.com, luto@...nel.org, peterz@...radead.org,
        rppt@...ux.ibm.com, akpm@...ux-foundation.org, hughd@...gle.com,
        ebiederm@...ssion.com, masahiroy@...nel.org, ardb@...nel.org,
        ndesaulniers@...gle.com, dima@...ovin.in, daniel.kiper@...cle.com,
        nivedita@...m.mit.edu, rafael.j.wysocki@...el.com,
        dan.j.williams@...el.com, zhenzhong.duan@...cle.com,
        jroedel@...e.de, bhe@...hat.com, guro@...com,
        Thomas.Lendacky@....com, andriy.shevchenko@...ux.intel.com,
        keescook@...omium.org, hannes@...xchg.org, minchan@...nel.org,
        mhocko@...nel.org, ying.huang@...el.com,
        yang.shi@...ux.alibaba.com, gustavo@...eddedor.com,
        ziqian.lzq@...fin.com, vdavydov.dev@...il.com,
        jason.zeng@...el.com, kevin.tian@...el.com, zhiyuan.lv@...el.com,
        lei.l.li@...el.com, paul.c.lai@...el.com, ashok.raj@...el.com,
        linux-fsdevel@...r.kernel.org, linux-doc@...r.kernel.org,
        kexec@...ts.infradead.org
Subject: [RFC 43/43] PKRAM: improve index alignment of pkram_link entries

To take advantage of optimizations when adding pages to the page cache
via shmem_insert_pages(), improve the likelihood that the pages array
passed to shmem_insert_pages() starts on an aligned index.  Do this
when preserving pages by starting a new pkram_link page when the current
page is aligned and the next aligned page will not fit on the pkram_link
page.

Signed-off-by: Anthony Yznaga <anthony.yznaga@...cle.com>
---
 mm/pkram.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/mm/pkram.c b/mm/pkram.c
index ef092aa5ce7a..416c3ca4411b 100644
--- a/mm/pkram.c
+++ b/mm/pkram.c
@@ -913,11 +913,21 @@ static int __pkram_save_page(struct pkram_stream *ps,
 {
 	struct pkram_link *link = ps->link;
 	struct pkram_obj *obj = ps->obj;
+	int order, align, align_cnt;
 	pkram_entry_t p;
-	int order;
+
+	if (PageTransHuge(page)) {
+		align = 1 << (HPAGE_PMD_ORDER + XA_CHUNK_SHIFT - (HPAGE_PMD_ORDER % XA_CHUNK_SHIFT));
+		align_cnt = align >> HPAGE_PMD_ORDER;
+	} else {
+		align = XA_CHUNK_SIZE;
+		align_cnt = XA_CHUNK_SIZE;
+	}
 
 	if (!link || ps->entry_idx >= PKRAM_LINK_ENTRIES_MAX ||
-	    index != ps->next_index) {
+	    index != ps->next_index ||
+	    (IS_ALIGNED(index, align) &&
+	    (ps->entry_idx + align_cnt > PKRAM_LINK_ENTRIES_MAX))) {
 		struct page *link_page;
 
 		link_page = pkram_alloc_page((ps->gfp_mask & GFP_RECLAIM_MASK) |
-- 
2.13.3

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