From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f200.google.com (mail-pf0-f200.google.com [209.85.192.200]) by kanga.kvack.org (Postfix) with ESMTP id 104D66B0263 for ; Sat, 22 Oct 2016 11:17:42 -0400 (EDT) Received: by mail-pf0-f200.google.com with SMTP id e6so79231187pfk.2 for ; Sat, 22 Oct 2016 08:17:42 -0700 (PDT) Received: from bombadil.infradead.org (bombadil.infradead.org. [2001:1868:205::9]) by mx.google.com with ESMTPS id p125si7308909pfp.267.2016.10.22.08.17.41 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 22 Oct 2016 08:17:41 -0700 (PDT) From: Christoph Hellwig 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> In-Reply-To: <1477149440-12478-1-git-send-email-hch@lst.de> References: <1477149440-12478-1-git-send-email-hch@lst.de> Sender: owner-linux-mm@kvack.org List-ID: 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 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org