From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f199.google.com (mail-pf0-f199.google.com [209.85.192.199]) by kanga.kvack.org (Postfix) with ESMTP id 1997B6B0268 for ; Mon, 24 Oct 2016 20:14:18 -0400 (EDT) Received: by mail-pf0-f199.google.com with SMTP id 128so133709395pfz.1 for ; Mon, 24 Oct 2016 17:14:18 -0700 (PDT) Received: from mga11.intel.com (mga11.intel.com. [192.55.52.93]) by mx.google.com with ESMTPS id p187si17912762pfg.145.2016.10.24.17.14.17 for (version=TLS1 cipher=AES128-SHA bits=128/128); Mon, 24 Oct 2016 17:14:17 -0700 (PDT) From: "Kirill A. Shutemov" Subject: [PATCHv4 17/43] HACK: readahead: alloc huge pages, if allowed Date: Tue, 25 Oct 2016 03:13:16 +0300 Message-Id: <20161025001342.76126-18-kirill.shutemov@linux.intel.com> In-Reply-To: <20161025001342.76126-1-kirill.shutemov@linux.intel.com> References: <20161025001342.76126-1-kirill.shutemov@linux.intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: Theodore Ts'o , Andreas Dilger , Jan Kara , Andrew Morton Cc: Alexander Viro , Hugh Dickins , Andrea Arcangeli , Dave Hansen , Vlastimil Babka , Matthew Wilcox , Ross Zwisler , linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-block@vger.kernel.org, "Kirill A. Shutemov" Most page cache allocation happens via readahead (sync or async), so if we want to have significant number of huge pages in page cache we need to find a ways to allocate them from readahead. Unfortunately, huge pages doesn't fit into current readahead design: 128 max readahead window, assumption on page size, PageReadahead() to track hit/miss. I haven't found a ways to get it right yet. This patch just allocates huge page if allowed, but doesn't really provide any readahead if huge page is allocated. We read out 2M a time and I would expect spikes in latancy without readahead. Therefore HACK. Having that said, I don't think it should prevent huge page support to be applied. Future will show if lacking readahead is a big deal with huge pages in page cache. Any suggestions are welcome. Signed-off-by: Kirill A. Shutemov --- mm/readahead.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) diff --git a/mm/readahead.c b/mm/readahead.c index c8a955b1297e..f46a9080f6a9 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -174,6 +174,21 @@ int __do_page_cache_readahead(struct address_space *mapping, struct file *filp, if (page_offset > end_index) break; + if (IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE) && + (!page_idx || !(page_offset % HPAGE_PMD_NR)) && + page_cache_allow_huge(mapping, page_offset)) { + page = __page_cache_alloc_order(gfp_mask | __GFP_COMP, + HPAGE_PMD_ORDER); + if (page) { + prep_transhuge_page(page); + page->index = round_down(page_offset, + HPAGE_PMD_NR); + list_add(&page->lru, &page_pool); + ret++; + goto start_io; + } + } + rcu_read_lock(); page = radix_tree_lookup(&mapping->page_tree, page_offset); rcu_read_unlock(); @@ -189,7 +204,7 @@ int __do_page_cache_readahead(struct address_space *mapping, struct file *filp, SetPageReadahead(page); ret++; } - +start_io: /* * Now start the IO. We ignore I/O errors - if the page is not * uptodate then the caller will launch readpage again, and -- 2.9.3 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org