From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx2.suse.de ([195.135.220.15]:38928 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726254AbfKNN4n (ORCPT ); Thu, 14 Nov 2019 08:56:43 -0500 Date: Thu, 14 Nov 2019 14:56:41 +0100 From: Michal Hocko Subject: Re: [PATCH] mm/vmalloc: Fix regression caused by needless vmalloc_sync_all() Message-ID: <20191114135641.GA1356@dhcp22.suse.cz> References: <20191113095530.228959-1-shile.zhang@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191113095530.228959-1-shile.zhang@linux.alibaba.com> Sender: linux-kbuild-owner@vger.kernel.org List-ID: To: Shile Zhang Cc: Andrew Morton , Joerg Roedel , linux-mm@kvack.org, linux-kbuild@vger.kernel.org On Wed 13-11-19 17:55:30, Shile Zhang wrote: > vmalloc_sync_all() was put in the common path in > __purge_vmap_area_lazy(), for one sync issue only happened on X86_32 > with PTI enabled. It is needless for X86_64, which caused a big regression > in UnixBench Shell8 testing on X86_64. > Similar regression also reported by 0-day kernel test robot in reaim > benchmarking: > https://lists.01.org/hyperkitty/list/lkp@lists.01.org/thread/4D3JPPHBNOSPFK2KEPC6KGKS6J25AIDB/ > > Fix it by adding more conditions. This doesn't really explain a lot. Could you explain why the syncing should be limited only to PAE and !SHARED_KERNEL_PMD? > Fixes: 3f8fd02b1bf1 ("mm/vmalloc: Sync unmappings in __purge_vmap_area_lazy()") > > Signed-off-by: Shile Zhang > --- > mm/vmalloc.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index a3c70e275f4e..7b9fc7966da6 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -1255,11 +1255,17 @@ static bool __purge_vmap_area_lazy(unsigned long start, unsigned long end) > if (unlikely(valist == NULL)) > return false; > > +#if defined(CONFIG_X86_32) && defined(CONFIG_X86_PAE) > /* > * First make sure the mappings are removed from all page-tables > * before they are freed. > + * > + * This is only needed on x86-32 with !SHARED_KERNEL_PMD, which is > + * the case on a PAE kernel with PTI enabled. > */ > - vmalloc_sync_all(); > + if (!SHARED_KERNEL_PMD && boot_cpu_has(X86_FEATURE_PTI)) > + vmalloc_sync_all(); > +#endif > > /* > * TODO: to calculate a flush range without looping. > -- > 2.24.0.rc2 > -- Michal Hocko SUSE Labs