From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752626Ab2ABKZu (ORCPT ); Mon, 2 Jan 2012 05:25:50 -0500 Received: from mail-ee0-f46.google.com ([74.125.83.46]:55270 "EHLO mail-ee0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752115Ab2ABKZa (ORCPT ); Mon, 2 Jan 2012 05:25:30 -0500 From: Gilad Ben-Yossef To: linux-kernel@vger.kernel.org Cc: Gilad Ben-Yossef , Christoph Lameter , Chris Metcalf , Peter Zijlstra , Frederic Weisbecker , Russell King , linux-mm@kvack.org, Pekka Enberg , Matt Mackall , Sasha Levin , Rik van Riel , Andi Kleen , Mel Gorman , Andrew Morton , Alexander Viro , linux-fsdevel@vger.kernel.org, Avi Kivity Subject: [PATCH v5 6/8] fs: only send IPI to invalidate LRU BH when needed Date: Mon, 2 Jan 2012 12:24:17 +0200 Message-Id: <1325499859-2262-7-git-send-email-gilad@benyossef.com> X-Mailer: git-send-email 1.7.0.4 In-Reply-To: <1325499859-2262-1-git-send-email-gilad@benyossef.com> References: <1325499859-2262-1-git-send-email-gilad@benyossef.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In several code paths, such as when unmounting a file system (but not only) we send an IPI to ask each cpu to invalidate its local LRU BHs. For multi-cores systems that have many cpus that may not have any LRU BH because they are idle or because they have no performed any file system access since last invalidation (e.g. CPU crunching on high perfomance computing nodes that write results to shared memory) this can lead to loss of performance each time someone switches KVM (the virtual keyboard and screen type, not the hypervisor) that has a USB storage stuck in. This patch attempts to only send the IPI to cpus that have LRU BH. Signed-off-by: Gilad Ben-Yossef CC: Christoph Lameter CC: Chris Metcalf CC: Peter Zijlstra CC: Frederic Weisbecker CC: Russell King CC: linux-mm@kvack.org CC: Pekka Enberg CC: Matt Mackall CC: Sasha Levin CC: Rik van Riel CC: Andi Kleen CC: Mel Gorman CC: Andrew Morton CC: Alexander Viro CC: linux-fsdevel@vger.kernel.org CC: Avi Kivity --- fs/buffer.c | 15 ++++++++++++++- 1 files changed, 14 insertions(+), 1 deletions(-) diff --git a/fs/buffer.c b/fs/buffer.c index 19d8eb7..b2378d4 100644 --- a/fs/buffer.c +++ b/fs/buffer.c @@ -1434,10 +1434,23 @@ static void invalidate_bh_lru(void *arg) } put_cpu_var(bh_lrus); } + +static int local_bh_lru_avail(int cpu, void *dummy) +{ + struct bh_lru *b = per_cpu_ptr(&bh_lrus, cpu); + int i; + for (i = 0; i < BH_LRU_SIZE; i++) { + if (b->bhs[i]) + return 1; + } + + return 0; +} + void invalidate_bh_lrus(void) { - on_each_cpu(invalidate_bh_lru, NULL, 1); + on_each_cpu_cond(local_bh_lru_avail, invalidate_bh_lru, NULL, 1); } EXPORT_SYMBOL_GPL(invalidate_bh_lrus); -- 1.7.0.4