Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759217AbcKCVEg (ORCPT ); Thu, 3 Nov 2016 17:04:36 -0400 Received: from mail-pf0-f193.google.com ([209.85.192.193]:34524 "EHLO mail-pf0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755881AbcKCVEf (ORCPT ); Thu, 3 Nov 2016 17:04:35 -0400 Date: Thu, 3 Nov 2016 22:04:28 +0100 From: Vitaly Wool To: Linux-MM , linux-kernel@vger.kernel.org Cc: Dan Streetman , Andrew Morton Subject: [PATH] z3fold: extend compaction function Message-Id: <20161103220428.984a8d09d0c9569e6bc6b8cc@gmail.com> X-Mailer: Sylpheed 3.4.1 (GTK+ 2.24.23; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2839 Lines: 94 z3fold_compact_page() currently only handles the situation when there's a single middle chunk within the z3fold page. However it may be worth it to move middle chunk closer to either first or last chunk, whichever is there, if the gap between them is big enough. This patch adds the relevant code, using BIG_CHUNK_GAP define as a threshold for middle chunk to be worth moving. Signed-off-by: Vitaly Wool --- mm/z3fold.c | 60 +++++++++++++++++++++++++++++++++++++++++++++++------------- 1 file changed, 47 insertions(+), 13 deletions(-) diff --git a/mm/z3fold.c b/mm/z3fold.c index 4d02280..fea6791 100644 --- a/mm/z3fold.c +++ b/mm/z3fold.c @@ -250,26 +250,60 @@ static void z3fold_destroy_pool(struct z3fold_pool *pool) kfree(pool); } +static inline void *mchunk_memmove(struct z3fold_header *zhdr, + unsigned short dst_chunk) +{ + void *beg = zhdr; + return memmove(beg + (dst_chunk << CHUNK_SHIFT), + beg + (zhdr->start_middle << CHUNK_SHIFT), + zhdr->middle_chunks << CHUNK_SHIFT); +} + +#define BIG_CHUNK_GAP 3 /* Has to be called with lock held */ static int z3fold_compact_page(struct z3fold_header *zhdr) { struct page *page = virt_to_page(zhdr); - void *beg = zhdr; + int ret = 0; + + if (test_bit(MIDDLE_CHUNK_MAPPED, &page->private)) + goto out; + if (zhdr->middle_chunks != 0) { + if (zhdr->first_chunks == 0 && zhdr->last_chunks == 0) { + mchunk_memmove(zhdr, 1); /* move to the beginning */ + zhdr->first_chunks = zhdr->middle_chunks; + zhdr->middle_chunks = 0; + zhdr->start_middle = 0; + zhdr->first_num++; + ret = 1; + goto out; + } - if (!test_bit(MIDDLE_CHUNK_MAPPED, &page->private) && - zhdr->middle_chunks != 0 && - zhdr->first_chunks == 0 && zhdr->last_chunks == 0) { - memmove(beg + ZHDR_SIZE_ALIGNED, - beg + (zhdr->start_middle << CHUNK_SHIFT), - zhdr->middle_chunks << CHUNK_SHIFT); - zhdr->first_chunks = zhdr->middle_chunks; - zhdr->middle_chunks = 0; - zhdr->start_middle = 0; - zhdr->first_num++; - return 1; + /* + * moving data is expensive, so let's only do that if + * there's substantial gain (at least BIG_CHUNK_GAP chunks) + */ + if (zhdr->first_chunks != 0 && zhdr->last_chunks == 0 && + zhdr->start_middle > zhdr->first_chunks + BIG_CHUNK_GAP) { + mchunk_memmove(zhdr, zhdr->first_chunks + 1); + zhdr->start_middle = zhdr->first_chunks + 1; + ret = 1; + goto out; + } + if (zhdr->last_chunks != 0 && zhdr->first_chunks == 0 && + zhdr->middle_chunks + zhdr->last_chunks <= + NCHUNKS - zhdr->start_middle - BIG_CHUNK_GAP) { + unsigned short new_start = NCHUNKS - zhdr->last_chunks - + zhdr->middle_chunks; + mchunk_memmove(zhdr, new_start); + zhdr->start_middle = new_start; + ret = 1; + goto out; + } } - return 0; +out: + return ret; } /** -- 2.4.2