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=-15.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 E0EADC433E0 for ; Wed, 24 Feb 2021 20:03:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9EEA264F2A for ; Wed, 24 Feb 2021 20:03:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235242AbhBXUDV (ORCPT ); Wed, 24 Feb 2021 15:03:21 -0500 Received: from mail.kernel.org ([198.145.29.99]:55484 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235270AbhBXUC2 (ORCPT ); Wed, 24 Feb 2021 15:02:28 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 0DC9264E83; Wed, 24 Feb 2021 20:01:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1614196913; bh=ZJh8e4jsUNE/0SFEbgId4dpUQgEPbalDIanXSj7b92I=; h=Date:From:To:Subject:In-Reply-To:From; b=Y92M9F8CLjrxrWhIFwnor0e47wk4EE3fgS8zam6yfVbnaV6yDrAWRr0Qu5ALT72MD TSM0cPfQf3IgZEJf06ymxQv0T9KJluDWvaUf3WiG/Wyh2mkrsbKNDtT/7rObfRwOAx up+IOdv/QPc2ptukQNEgol3FFJx8zTMakcS6zFvU= Date: Wed, 24 Feb 2021 12:01:52 -0800 From: Andrew Morton To: akpm@linux-foundation.org, hch@lst.de, kent.overstreet@gmail.com, linmiaohe@huawei.com, linux-mm@kvack.org, mm-commits@vger.kernel.org, torvalds@linux-foundation.org, willy@infradead.org Subject: [patch 031/173] mm/filemap: remove dynamically allocated array from filemap_read Message-ID: <20210224200152.sbTamoMyG%akpm@linux-foundation.org> In-Reply-To: <20210224115824.1e289a6895087f10c41dd8d6@linux-foundation.org> User-Agent: s-nail v14.8.16 Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org From: "Matthew Wilcox (Oracle)" Subject: mm/filemap: remove dynamically allocated array from filemap_read Increasing the batch size runs into diminishing returns. It's probably better to make, eg, three calls to filemap_get_pages() than it is to call into kmalloc(). Link: https://lkml.kernel.org/r/20210122160140.223228-3-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: Christoph Hellwig Reviewed-by: Miaohe Lin Cc: Kent Overstreet Signed-off-by: Andrew Morton --- mm/filemap.c | 15 ++------------- 1 file changed, 2 insertions(+), 13 deletions(-) --- a/mm/filemap.c~mm-filemap-remove-dynamically-allocated-array-from-filemap_read +++ a/mm/filemap.c @@ -2431,8 +2431,8 @@ ssize_t generic_file_buffered_read(struc struct file_ra_state *ra = &filp->f_ra; struct address_space *mapping = filp->f_mapping; struct inode *inode = mapping->host; - struct page *pages_onstack[PAGEVEC_SIZE], **pages = NULL; - unsigned int nr_pages = min_t(unsigned int, 512, + struct page *pages[PAGEVEC_SIZE]; + unsigned int nr_pages = min_t(unsigned int, PAGEVEC_SIZE, ((iocb->ki_pos + iter->count + PAGE_SIZE - 1) >> PAGE_SHIFT) - (iocb->ki_pos >> PAGE_SHIFT)); int i, pg_nr, error = 0; @@ -2446,14 +2446,6 @@ ssize_t generic_file_buffered_read(struc iov_iter_truncate(iter, inode->i_sb->s_maxbytes); - if (nr_pages > ARRAY_SIZE(pages_onstack)) - pages = kmalloc_array(nr_pages, sizeof(void *), GFP_KERNEL); - - if (!pages) { - pages = pages_onstack; - nr_pages = min_t(unsigned int, nr_pages, ARRAY_SIZE(pages_onstack)); - } - do { cond_resched(); @@ -2538,9 +2530,6 @@ put_pages: file_accessed(filp); - if (pages != pages_onstack) - kfree(pages); - return written ? written : error; } EXPORT_SYMBOL_GPL(generic_file_buffered_read); _