Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [PATCH 00/11] Use global pages with PTI
To:     Thomas Gleixner <tglx@linutronix.de>
References: <20180323174447.55F35636@viggo.jf.intel.com>
 <CA+55aFwEC1O+6qRc35XwpcuLSgJ+0GP6ciqw_1Oc-msX=efLvQ@mail.gmail.com>
 <be2e683c-bf0a-e9ce-2f02-4905f6bd56d3@linux.intel.com>
 <alpine.DEB.2.21.1803271526260.1964@nanos.tec.linutronix.de>
 <c0e7ca0b-dcb5-66e2-9df6-f53e4eb22781@linux.intel.com>
 <alpine.DEB.2.21.1803271949250.1618@nanos.tec.linutronix.de>
 <20180327200719.lvdomez6hszpmo4s@gmail.com>
 <0d6ea030-ec3b-d649-bad7-89ff54094e25@linux.intel.com>
 <20180330120920.btobga44wqytlkoe@gmail.com>
 <20180330121725.zcklh36ulg7crydw@gmail.com>
 <3cdc23a2-99eb-6f93-6934-f7757fa30a3e@linux.intel.com>
 <alpine.DEB.2.21.1803302230560.1479@nanos.tec.linutronix.de>
Cc:     Ingo Molnar <mingo@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-mm <linux-mm@kvack.org>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Andrew Lutomirski <luto@kernel.org>,
        Kees Cook <keescook@google.com>,
        Hugh Dickins <hughd@google.com>,
        =?UTF-8?B?SsO8cmdlbiBHcm/Dnw==?= <jgross@suse.com>,
        the arch/x86 maintainers <x86@kernel.org>, namit@vmware.com
From:   Dave Hansen <dave.hansen@linux.intel.com>
Message-ID: <62a0dbae-75eb-6737-6029-4aaf72ebd199@linux.intel.com>
Date:   Fri, 30 Mar 2018 14:40:11 -0700
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101
 Thunderbird/52.6.0
MIME-Version: 1.0
In-Reply-To: <alpine.DEB.2.21.1803302230560.1479@nanos.tec.linutronix.de>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 03/30/2018 01:32 PM, Thomas Gleixner wrote:
> On Fri, 30 Mar 2018, Dave Hansen wrote:
> 
>> On 03/30/2018 05:17 AM, Ingo Molnar wrote:
>>> BTW., the expectation on !PCID Intel hardware would be for global pages to help 
>>> even more than the 0.6% and 1.7% you measured on PCID hardware: PCID already 
>>> _reduces_ the cost of TLB flushes - so if there's not even PCID then global pages 
>>> should help even more.
>>>
>>> In theory at least. Would still be nice to measure it.
>>
>> I did the lseek test on a modern, non-PCID system:
>>
>> No Global pages (baseline): 6077741 lseeks/sec
>> 94 Global pages (this set): 8433111 lseeks/sec
>> 			   +2355370 lseeks/sec (+38.8%)
> 
> That's all kernel text, right? What's the result for the case where global
> is only set for all user/kernel shared pages?

Yes, that's all kernel text (94 global entries).  Here's the number with
just the entry data/text set global (88 global entries on this system):

No Global pages (baseline): 6077741 lseeks/sec
88 Global Pages (kentry  ): 7528609 lseeks/sec (+23.9%)
94 Global pages (this set): 8433111 lseeks/sec (+38.8%)