Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965045AbcJVPRo (ORCPT ); Sat, 22 Oct 2016 11:17:44 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:38169 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965024AbcJVPRl (ORCPT ); Sat, 22 Oct 2016 11:17:41 -0400 From: Christoph Hellwig To: akpm@linux-foundation.org Cc: joelaf@google.com, jszhang@marvell.com, chris@chris-wilson.co.uk, joaodias@google.com, linux-mm@kvack.org, linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH 6/7] mm: turn vmap_purge_lock into a mutex Date: Sat, 22 Oct 2016 17:17:19 +0200 Message-Id: <1477149440-12478-7-git-send-email-hch@lst.de> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1477149440-12478-1-git-send-email-hch@lst.de> References: <1477149440-12478-1-git-send-email-hch@lst.de> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2179 Lines: 73 The purge_lock spinlock causes high latencies with non RT kernel. This has been reported multiple times on lkml [1] [2] and affects applications like audio. This patch replaces it with a mutex to allow preemption while holding the lock. Thanks to Joel Fernandes for the detailed report and analysis as well as an earlier attempt at fixing this issue. [1] http://lists.openwall.net/linux-kernel/2016/03/23/29 [2] https://lkml.org/lkml/2016/10/9/59 Signed-off-by: Christoph Hellwig Tested-by: Jisheng Zhang --- mm/vmalloc.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 0e7f523..23d6797 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -606,7 +606,7 @@ static atomic_t vmap_lazy_nr = ATOMIC_INIT(0); * by this look, but we want to avoid concurrent calls for performance * reasons and to make the pcpu_get_vm_areas more deterministic. */ -static DEFINE_SPINLOCK(vmap_purge_lock); +static DEFINE_MUTEX(vmap_purge_lock); /* for per-CPU blocks */ static void purge_fragmented_blocks_allcpus(void); @@ -660,9 +660,9 @@ static bool __purge_vmap_area_lazy(unsigned long start, unsigned long end) */ static void try_purge_vmap_area_lazy(void) { - if (spin_trylock(&vmap_purge_lock)) { + if (mutex_trylock(&vmap_purge_lock)) { __purge_vmap_area_lazy(ULONG_MAX, 0); - spin_unlock(&vmap_purge_lock); + mutex_unlock(&vmap_purge_lock); } } @@ -671,10 +671,10 @@ static void try_purge_vmap_area_lazy(void) */ static void purge_vmap_area_lazy(void) { - spin_lock(&vmap_purge_lock); + mutex_lock(&vmap_purge_lock); purge_fragmented_blocks_allcpus(); __purge_vmap_area_lazy(ULONG_MAX, 0); - spin_unlock(&vmap_purge_lock); + mutex_unlock(&vmap_purge_lock); } /* @@ -1063,11 +1063,11 @@ void vm_unmap_aliases(void) rcu_read_unlock(); } - spin_lock(&vmap_purge_lock); + mutex_lock(&vmap_purge_lock); purge_fragmented_blocks_allcpus(); if (!__purge_vmap_area_lazy(start, end) && flush) flush_tlb_kernel_range(start, end); - spin_unlock(&vmap_purge_lock); + mutex_unlock(&vmap_purge_lock); } EXPORT_SYMBOL_GPL(vm_unmap_aliases); -- 2.1.4