From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id F136EC33CBA for ; Mon, 13 Jan 2020 15:37:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C68D221739 for ; Mon, 13 Jan 2020 15:37:58 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="h5nnknDp" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728808AbgAMPhy (ORCPT ); Mon, 13 Jan 2020 10:37:54 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:57854 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728789AbgAMPhx (ORCPT ); Mon, 13 Jan 2020 10:37:53 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From:Sender :Reply-To:Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From :Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help: List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=dOAadIMTUupd20Eg2Q5RqFxOIthPxhUDYq6Q/juU65U=; b=h5nnknDpxtg47EUFlq9egYwY2Q BVp+XqvUz3RyOjCxys3SgxE+ritoHjVvgyDZ36NkMrrrwfr2kC2knN1NP0CoGkVdvtuFhj2Yvf4tA VjSYy3z+eL3rL11kVEmD7VKk1EGwVF9GyZ7wc8sscVYOXXEURYqq314o60EJJWx/6ToUW5CoKJjAn DpuvjUPQ5hkFpWzMcnaTNX+I0A70aAjno35EMwqvH8u+pFuUGSYiQjJrf8chJCmwN5w6GYyvu31GU pa2Kqn/JHsmhmGP6MdHRRtR0ZidTpsH5FAet4RtCa4BKvSNH4Xi2reB0reKS+G7/yxIkwXXkq0YYg vYkIgTuw==; Received: from willy by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1ir1mr-00075z-5B; Mon, 13 Jan 2020 15:37:53 +0000 From: Matthew Wilcox To: linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Cc: "Matthew Wilcox (Oracle)" , jlayton@kernel.org, hch@infradead.org Subject: [PATCH 3/8] mm: Use a pagevec for readahead Date: Mon, 13 Jan 2020 07:37:41 -0800 Message-Id: <20200113153746.26654-4-willy@infradead.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20200113153746.26654-1-willy@infradead.org> References: <20200113153746.26654-1-willy@infradead.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-xfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org From: "Matthew Wilcox (Oracle)" Instead of using a linked list, use a small array. This does mean we will allocate and then submit for I/O no more than 15 pages at a time (60kB), but we have the block queue plugged so the bios can be combined afterwards. We generally don't readahead more than 256kB anyway, so this is not a huge reduction in efficiency, and we'll make up for it with later patches. Signed-off-by: Matthew Wilcox (Oracle) --- mm/readahead.c | 97 +++++++++++++++++++++++++++----------------------- 1 file changed, 52 insertions(+), 45 deletions(-) diff --git a/mm/readahead.c b/mm/readahead.c index 6bf73ef33b7e..76a70a4406b5 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -113,35 +113,37 @@ int read_cache_pages(struct address_space *mapping, struct list_head *pages, EXPORT_SYMBOL(read_cache_pages); -static int read_pages(struct address_space *mapping, struct file *filp, - struct list_head *pages, unsigned int nr_pages, gfp_t gfp) +/* + * We ignore I/O errors - they will be handled by the actual consumer of + * the data that we attempted to prefetch. + */ +static unsigned read_pages(struct address_space *mapping, struct file *filp, + struct pagevec *pvec, pgoff_t offset, gfp_t gfp) { - struct blk_plug plug; - unsigned page_idx; - int ret; - - blk_start_plug(&plug); + struct page *page; + unsigned int nr_pages = pagevec_count(pvec); if (mapping->a_ops->readpages) { - ret = mapping->a_ops->readpages(filp, mapping, pages, nr_pages); - /* Clean up the remaining pages */ - put_pages_list(pages); - goto out; - } + LIST_HEAD(pages); - for (page_idx = 0; page_idx < nr_pages; page_idx++) { - struct page *page = lru_to_page(pages); - list_del(&page->lru); - if (!add_to_page_cache_lru(page, mapping, page->index, gfp)) - mapping->a_ops->readpage(filp, page); - put_page(page); + pagevec_for_each(pvec, page) { + page->index = offset++; + list_add(&page->lru, &pages); + } + mapping->a_ops->readpages(filp, mapping, &pages, nr_pages); + /* Clean up the remaining pages */ + put_pages_list(&pages); + } else { + pagevec_for_each(pvec, page) { + if (!add_to_page_cache_lru(page, mapping, offset++, + gfp)) + mapping->a_ops->readpage(filp, page); + put_page(page); + } } - ret = 0; -out: - blk_finish_plug(&plug); - - return ret; + pagevec_reinit(pvec); + return nr_pages; } /* @@ -159,59 +161,64 @@ unsigned long __do_page_cache_readahead(struct address_space *mapping, struct inode *inode = mapping->host; struct page *page; unsigned long end_index; /* The last page we want to read */ - LIST_HEAD(page_pool); + struct pagevec pages; int page_idx; + pgoff_t page_offset = offset; unsigned long nr_pages = 0; loff_t isize = i_size_read(inode); gfp_t gfp_mask = readahead_gfp_mask(mapping); + struct blk_plug plug; + + blk_start_plug(&plug); if (isize == 0) goto out; end_index = ((isize - 1) >> PAGE_SHIFT); + pagevec_init(&pages); /* * Preallocate as many pages as we will need. */ for (page_idx = 0; page_idx < nr_to_read; page_idx++) { - pgoff_t page_offset = offset + page_idx; + page_offset++; if (page_offset > end_index) break; page = xa_load(&mapping->i_pages, page_offset); + + /* + * Page already present? Kick off the current batch of + * contiguous pages before continuing with the next batch. + */ if (page && !xa_is_value(page)) { - /* - * Page already present? Kick off the current batch of - * contiguous pages before continuing with the next - * batch. - */ - if (nr_pages) - read_pages(mapping, filp, &page_pool, nr_pages, - gfp_mask); - nr_pages = 0; + unsigned int count = pagevec_count(&pages); + + if (count) + nr_pages += read_pages(mapping, filp, &pages, + offset, gfp_mask); + offset = page_offset + 1; continue; } page = __page_cache_alloc(gfp_mask); if (!page) break; - page->index = page_offset; - list_add(&page->lru, &page_pool); + if (pagevec_add(&pages, page) == 0) { + nr_pages += read_pages(mapping, filp, &pages, + offset, gfp_mask); + offset = page_offset + 1; + } if (page_idx == nr_to_read - lookahead_size) SetPageReadahead(page); - nr_pages++; } - /* - * Now start the IO. We ignore I/O errors - if the page is not - * uptodate then the caller will launch readpage again, and - * will then handle the error. - */ - if (nr_pages) - read_pages(mapping, filp, &page_pool, nr_pages, gfp_mask); - BUG_ON(!list_empty(&page_pool)); + if (pagevec_count(&pages)) + nr_pages += read_pages(mapping, filp, &pages, offset, gfp_mask); out: + blk_finish_plug(&plug); + return nr_pages; } -- 2.24.1