From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753404AbbDUKlf (ORCPT ); Tue, 21 Apr 2015 06:41:35 -0400 Received: from cantor2.suse.de ([195.135.220.15]:34108 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752775AbbDUKl3 (ORCPT ); Tue, 21 Apr 2015 06:41:29 -0400 From: Mel Gorman To: Linux-MM Cc: Rik van Riel , Hugh Dickins , Minchan Kim , Dave Hansen , Andi Kleen , LKML , Mel Gorman Subject: [PATCH 6/6] mm: Gather more PFNs before sending a TLB to flush unmapped pages Date: Tue, 21 Apr 2015 11:41:20 +0100 Message-Id: <1429612880-21415-7-git-send-email-mgorman@suse.de> X-Mailer: git-send-email 2.1.2 In-Reply-To: <1429612880-21415-1-git-send-email-mgorman@suse.de> References: <1429612880-21415-1-git-send-email-mgorman@suse.de> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The patch "mm: Send a single IPI to TLB flush multiple pages when unmapping" would batch 32 pages before sending an IPI. This patch increases the size of the data structure to hold a pages worth of PFNs before sending an IPI. This is a trade-off between memory usage and reducing IPIS sent. In the ideal case where multiple processes are reading large mapped files, this patch reduces interrupts/second from roughly 180K per second to 60K per second. Signed-off-by: Mel Gorman Reviewed-by: Rik van Riel --- include/linux/sched.h | 9 +++++---- kernel/fork.c | 6 ++++-- mm/vmscan.c | 5 +++-- 3 files changed, 12 insertions(+), 8 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index 5c09db02fe78..3e4d3f545005 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1275,16 +1275,17 @@ enum perf_event_task_context { perf_nr_task_contexts, }; -/* Matches SWAP_CLUSTER_MAX but refined to limit header dependencies */ -#define BATCH_TLBFLUSH_SIZE 32UL - /* Track pages that require TLB flushes */ struct tlbflush_unmap_batch { struct cpumask cpumask; unsigned long nr_pages; - unsigned long pfns[BATCH_TLBFLUSH_SIZE]; + unsigned long pfns[0]; }; +/* alloc_tlb_ubc() always allocates a page */ +#define BATCH_TLBFLUSH_SIZE \ + ((PAGE_SIZE - sizeof(struct tlbflush_unmap_batch)) / sizeof(unsigned long)) + struct task_struct { volatile long state; /* -1 unrunnable, 0 runnable, >0 stopped */ void *stack; diff --git a/kernel/fork.c b/kernel/fork.c index 86c872fec9fb..f260663f209a 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -247,8 +247,10 @@ void __put_task_struct(struct task_struct *tsk) put_signal_struct(tsk->signal); #ifdef CONFIG_ARCH_SUPPORTS_LOCAL_TLB_PFN_FLUSH - kfree(tsk->tlb_ubc); - tsk->tlb_ubc = NULL; + if (tsk->tlb_ubc) { + free_page((unsigned long)tsk->tlb_ubc); + tsk->tlb_ubc = NULL; + } #endif if (!profile_handoff_task(tsk)) diff --git a/mm/vmscan.c b/mm/vmscan.c index e39e7c4bf548..080ba929049c 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2775,14 +2775,15 @@ out: /* * Allocate the control structure for batch TLB flushing. An allocation * failure is harmless as the reclaimer will send IPIs where necessary. + * If the allocation size changes then update BATCH_TLBFLUSH_SIZE. */ void alloc_tlb_ubc(void) { if (current->tlb_ubc) return; - current->tlb_ubc = kmalloc(sizeof(struct tlbflush_unmap_batch), - GFP_ATOMIC | __GFP_NOWARN); + current->tlb_ubc = (struct tlbflush_unmap_batch *) + __get_free_page(GFP_KERNEL | __GFP_NOWARN); if (!current->tlb_ubc) return; -- 2.1.2