From: Song Liu <songliubraving@fb.com>
To: Dave Hansen <dave.hansen@intel.com>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux MM <linux-mm@kvack.org>, Kernel Team <Kernel-team@fb.com>,
"stable@vger.kernel.org" <stable@vger.kernel.org>,
Joerg Roedel <jroedel@suse.de>,
Thomas Gleixner <tglx@linutronix.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
Andy Lutomirski <luto@kernel.org>,
"Peter Zijlstra" <peterz@infradead.org>
Subject: Re: [PATCH] x86/mm/pti: in pti_clone_pgtable() don't increase addr by PUD_SIZE
Date: Tue, 20 Aug 2019 16:05:45 +0000 [thread overview]
Message-ID: <CCFAB5E0-263E-4D9F-92A5-51922EF5998C@fb.com> (raw)
In-Reply-To: <463379e3-5a31-5064-dd02-ea2fe149fa7e@intel.com>
> On Aug 20, 2019, at 7:18 AM, Dave Hansen <dave.hansen@intel.com> wrote:
>
> On 8/20/19 7:14 AM, Song Liu wrote:
>>> *But*, that shouldn't get hit on a Skylake CPU since those have PCIDs
>>> and shouldn't have a global kernel image. Could you confirm whether
>>> PCIDs are supported on this CPU?
>> Yes, pcid is listed in /proc/cpuinfo.
>
> So what's going on? Could you confirm exactly which pti_clone_pgtable()
> is causing you problems? Do you have a theory as to why this manifests
> as a performance problem rather than a functional one?
>
> A diff of these:
>
> /sys/kernel/debug/page_tables/current_user
> /sys/kernel/debug/page_tables/current_kernel
>
> before and after your patch might be helpful.
I believe the difference is from the following entries (7 PMDs)
Before the patch:
current_kernel: 0xffffffff81000000-0xffffffff81e04000 14352K ro GLB x pte
efi: 0xffffffff81000000-0xffffffff81e04000 14352K ro GLB x pte
kernel: 0xffffffff81000000-0xffffffff81e04000 14352K ro GLB x pte
After the patch:
current_kernel: 0xffffffff81000000-0xffffffff81e00000 14M ro PSE GLB x pmd
efi: 0xffffffff81000000-0xffffffff81e00000 14M ro PSE GLB x pmd
kernel: 0xffffffff81000000-0xffffffff81e00000 14M ro PSE GLB x pmd
current_kernel and kernel show same data though.
Thanks,
Song
next prev parent reply other threads:[~2019-08-20 16:05 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-20 7:51 Song Liu
2019-08-20 9:12 ` Thomas Gleixner
2019-08-20 13:17 ` Song Liu
2019-08-20 10:00 ` Peter Zijlstra
2019-08-20 11:16 ` Thomas Gleixner
2019-08-20 13:21 ` Song Liu
2019-08-20 13:39 ` Thomas Gleixner
2019-08-20 13:55 ` Rik van Riel
2019-08-20 14:00 ` Song Liu
2019-08-20 16:56 ` [PATCH v2] " Rik van Riel
2019-08-20 13:21 ` [PATCH] " Rik van Riel
2019-08-20 13:19 ` Song Liu
2019-08-20 13:57 ` Dave Hansen
2019-08-20 14:14 ` Song Liu
2019-08-20 14:18 ` Dave Hansen
2019-08-20 16:05 ` Song Liu [this message]
2019-08-20 16:38 ` Song Liu
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