linux-kernel - Re: Performance regressions in "boot

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Message-ID: <DM6PR05MB52920B2D4267AD7D073D3C36A4FF0@DM6PR05MB5292.namprd05.prod.outlook.com>
Date:   Fri, 20 Nov 2020 03:11:11 +0000
From:   Rahul Gopakumar <gopakumarr@...are.com>
To:     "bhe@...hat.com" <bhe@...hat.com>
CC:     "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "natechancellor@...il.com" <natechancellor@...il.com>,
        "ndesaulniers@...gle.com" <ndesaulniers@...gle.com>,
        "clang-built-linux@...glegroups.com" 
        <clang-built-linux@...glegroups.com>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>,
        Rajender M <manir@...are.com>,
        Yiu Cho Lau <lauyiuch@...are.com>,
        Peter Jonasson <pjonasson@...are.com>,
        Venkatesh Rajaram <rajaramv@...are.com>
Subject: Re: Performance regressions in "boot_time" tests in Linux 5.8 Kernel

Hi Baoquan,

To which commit should we apply the draft patch. We tried applying
the patch to the commit 3e4fb4346c781068610d03c12b16c0cfb0fd24a3
(the one we used for applying the previous patch) but it fails.


From: bhe@...hat.com <bhe@...hat.com>
Sent: 12 November 2020 8:21 PM
To: Rahul Gopakumar <gopakumarr@...are.com>
Cc: linux-mm@...ck.org <linux-mm@...ck.org>; linux-kernel@...r.kernel.org <linux-kernel@...r.kernel.org>; akpm@...ux-foundation.org <akpm@...ux-foundation.org>; natechancellor@...il.com <natechancellor@...il.com>; ndesaulniers@...gle.com <ndesaulniers@...gle.com>; clang-built-linux@...glegroups.com <clang-built-linux@...glegroups.com>; rostedt@...dmis.org <rostedt@...dmis.org>; Rajender M <manir@...are.com>; Yiu Cho Lau <lauyiuch@...are.com>; Peter Jonasson <pjonasson@...are.com>; Venkatesh Rajaram <rajaramv@...are.com>
Subject: Re: Performance regressions in "boot_time" tests in Linux 5.8 Kernel 
 
On 11/03/20 at 12:34pm, Rahul Gopakumar wrote:
> >> So, you mean with the draft patch applied, the initial performance
> regression goes away, just many page corruption errors with call trace
> are seen, right?
> 
> Yes, that's right.
> 
> >> And the performance regression is about 2sec delay in
> your system?
> 
> The delay due to this new page corruption issue is about
> 3 secs.
> 
> Here is the summary
> 
> * Initial problem - 2 secs
> * Draft patch - Fixes initial problem (recovers 2 secs) but
> brings in new page corruption issue (3 secs)
> 
> >> Could you tell how you setup vmware VM so that I can ask our QA for
> help to create a vmware VM for me to test?
> 
> * Use vSphere ESXi 6.7 or 7.0 GA.
> * Create VM using vSphere Web Client and specify 1TB VM Memory.
> * Install RHEL 8.1, that's the guest used in this test.

Can you try the attached draft patch?

> 
> With draft patch, you should be able to reproduce the issue.
> Let me know if you need more details.