Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753676AbbGBIsb (ORCPT ); Thu, 2 Jul 2015 04:48:31 -0400 Received: from cantor2.suse.de ([195.135.220.15]:37450 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752999AbbGBIrZ (ORCPT ); Thu, 2 Jul 2015 04:47:25 -0400 From: Vlastimil Babka To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, Andrew Morton , Hugh Dickins , Andrea Arcangeli , "Kirill A. Shutemov" , Rik van Riel , Mel Gorman , David Rientjes , Joonsoo Kim , Vlastimil Babka Subject: [RFC 4/4] mm, thp: check hugepage availability for fault allocations Date: Thu, 2 Jul 2015 10:46:35 +0200 Message-Id: <1435826795-13777-5-git-send-email-vbabka@suse.cz> X-Mailer: git-send-email 2.4.3 In-Reply-To: <1435826795-13777-1-git-send-email-vbabka@suse.cz> References: <1435826795-13777-1-git-send-email-vbabka@suse.cz> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4794 Lines: 135 Since we track hugepage availability for khugepaged THP collapses, we can use it also for page fault THP allocations. If hugepages are considered unavailable on a node, the cost of reclaim/compaction during the page fault could be easily higher than any THP benefits (if it at all succeeds), so we better fallback to base pages instead. We clear the THP availability flag for a node if we do attempt and fail to allocate during page fault. Kcompactd is woken up both in the case of attempt skipped due to assumed non-availability, and for the truly failed allocation. This is to fully translate the need for hugepages into kcompactd activity. With this patch we also set the availability flag if we are freeing a large enough page from any context, to prevent false negatives after e.g. a process quits and another immediately starts. This does not consider high-order pages created by buddy merging, as that would need modifying the fast path and is unlikely to make much difference. Note that in case of false-positive hugepage availability, the allocation attempt may still result in a limited direct compaction, depending on /sys/kernel/mm/transparent_hugepage/defrag which defaults to "always". The default could be later changed to e.g. "madvise" to eliminate all of the page fault latency related to THP and rely exlusively on kcompactd. Also restructure alloc_pages_vma() a bit. Signed-off-by: Vlastimil Babka --- mm/mempolicy.c | 42 +++++++++++++++++++++++++++--------------- mm/page_alloc.c | 3 +++ 2 files changed, 30 insertions(+), 15 deletions(-) diff --git a/mm/mempolicy.c b/mm/mempolicy.c index 7477432..502e173 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -94,6 +94,7 @@ #include #include #include +#include #include #include @@ -1963,17 +1964,34 @@ alloc_pages_vma(gfp_t gfp, int order, struct vm_area_struct *vma, unsigned long addr, int node, bool hugepage) { struct mempolicy *pol; - struct page *page; + struct page *page = NULL; unsigned int cpuset_mems_cookie; struct zonelist *zl; nodemask_t *nmask; + /* Help compiler eliminate code */ + hugepage = IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && hugepage; + retry_cpuset: pol = get_vma_policy(vma, addr); cpuset_mems_cookie = read_mems_allowed_begin(); - if (unlikely(IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && hugepage && - pol->mode != MPOL_INTERLEAVE)) { + if (pol->mode == MPOL_INTERLEAVE) { + unsigned nid; + + nid = interleave_nid(pol, vma, addr, PAGE_SHIFT + order); + mpol_cond_put(pol); + if (!hugepage || thp_avail_isset(nid)) + page = alloc_page_interleave(gfp, order, nid); + if (hugepage && !page) { + thp_avail_clear(nid); + wakeup_kcompactd(nid, true); + } + goto out; + } + + nmask = policy_nodemask(gfp, pol); + if (hugepage) { /* * For hugepage allocation and non-interleave policy which * allows the current node, we only try to allocate from the @@ -1983,25 +2001,19 @@ alloc_pages_vma(gfp_t gfp, int order, struct vm_area_struct *vma, * If the policy is interleave, or does not allow the current * node in its nodemask, we allocate the standard way. */ - nmask = policy_nodemask(gfp, pol); if (!nmask || node_isset(node, *nmask)) { mpol_cond_put(pol); - page = alloc_pages_exact_node(node, + if (thp_avail_isset(node)) + page = alloc_pages_exact_node(node, gfp | __GFP_THISNODE, order); + if (!page) { + thp_avail_clear(node); + wakeup_kcompactd(node, true); + } goto out; } } - if (pol->mode == MPOL_INTERLEAVE) { - unsigned nid; - - nid = interleave_nid(pol, vma, addr, PAGE_SHIFT + order); - mpol_cond_put(pol); - page = alloc_page_interleave(gfp, order, nid); - goto out; - } - - nmask = policy_nodemask(gfp, pol); zl = policy_zonelist(gfp, pol, node); mpol_cond_put(pol); page = __alloc_pages_nodemask(gfp, order, zl, nmask); diff --git a/mm/page_alloc.c b/mm/page_alloc.c index d9cd834..ccd87b2 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -830,6 +830,9 @@ static void __free_pages_ok(struct page *page, unsigned int order) set_freepage_migratetype(page, migratetype); free_one_page(page_zone(page), page, pfn, order, migratetype); local_irq_restore(flags); + if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) + && order >= HPAGE_PMD_ORDER) + thp_avail_set(page_to_nid(page)); } void __init __free_pages_bootmem(struct page *page, unsigned int order) -- 2.4.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/