From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752687AbcGYOjt (ORCPT ); Mon, 25 Jul 2016 10:39:49 -0400 Received: from mx1.redhat.com ([209.132.183.28]:51955 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751418AbcGYOjn (ORCPT ); Mon, 25 Jul 2016 10:39:43 -0400 From: Kyle Walker To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, Kyle Walker , Andrew Morton , Michal Hocko , Geliang Tang , Vlastimil Babka , Roman Gushchin , "Kirill A. Shutemov" Subject: [PATCH] mm: Move readahead limit outside of readahead, and advisory syscalls Date: Mon, 25 Jul 2016 10:39:25 -0400 Message-Id: <1469457565-22693-1-git-send-email-kwalker@redhat.com> X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Mon, 25 Jul 2016 14:39:42 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Java workloads using the MappedByteBuffer library result in the fadvise() and madvise() syscalls being used extensively. Following recent readahead limiting alterations, such as 600e19af ("mm: use only per-device readahead limit") and 6d2be915 ("mm/readahead.c: fix readahead failure for memoryless NUMA nodes and limit readahead pages"), application performance suffers in instances where small readahead is configured. By moving this limit outside of the syscall codepaths, the syscalls are able to advise an inordinately large amount of readahead when desired. With a cap being imposed based on the half of NR_INACTIVE_FILE and NR_FREE_PAGES. In essence, allowing performance tuning efforts to define a small readahead limit, but then benefiting from large sequential readahead values selectively. Signed-off-by: Kyle Walker Cc: Andrew Morton Cc: Michal Hocko Cc: Geliang Tang Cc: Vlastimil Babka Cc: Roman Gushchin Cc: "Kirill A. Shutemov" --- mm/readahead.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/mm/readahead.c b/mm/readahead.c index 65ec288..6f8bb44 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -211,7 +211,9 @@ int force_page_cache_readahead(struct address_space *mapping, struct file *filp, if (unlikely(!mapping->a_ops->readpage && !mapping->a_ops->readpages)) return -EINVAL; - nr_to_read = min(nr_to_read, inode_to_bdi(mapping->host)->ra_pages); + nr_to_read = min(nr_to_read, (global_page_state(NR_INACTIVE_FILE) + + (global_page_state(NR_FREE_PAGES)) / 2)); + while (nr_to_read) { int err; @@ -484,6 +486,7 @@ void page_cache_sync_readahead(struct address_space *mapping, /* be dumb */ if (filp && (filp->f_mode & FMODE_RANDOM)) { + req_size = min(req_size, inode_to_bdi(mapping->host)->ra_pages); force_page_cache_readahead(mapping, filp, offset, req_size); return; } -- 2.5.5