linux-kernel - Re: Performance regressions in "boot

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Date:   Thu, 12 Nov 2020 22:51:49 +0800
From:   "bhe@...hat.com" <bhe@...hat.com>
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.


View attachment "0001-mm-make-memmap-defer-init-only-take-effect-per-zone.patch" of type "text/plain" (4653 bytes)