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From:   Shivank Garg <shivankgarg98@gmail.com>
Date:   Mon, 10 May 2021 20:27:07 +0530
Message-ID: <CAOVCmzGX54u4VLUSLt_yEM4E8MQNLwW4VTkNVurPXbCuQX6d_g@mail.gmail.com>
Subject: Profiling execution time for __alloc_pages_nodemask
To:     linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        akpm@linux-foundation.org, gregkh@linuxfoundation.org,
        sergey.senozhatsky@gmail.com, pmladek@suse.com, david@redhat.com
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Hi Everyone!

I want to profile the time taken to execute the __alloc_pages_nodemask
for different linux configurations/parameters.
To measure the execution time, I use the ktime_get() apis. I get the
ktime_get() on the top, and I want to do ktime_sub(ktime_get(),ktime)
and record it in a tracepoint.
However, the patch on implementation prevents the kernel from booting
up. I debugged the bug to find out that the issue recurs on adding
ktime_get() inside the __alloc_pages_nodemask path. So, that the
kernel fails to boot up ( and show the blank screen without any logs )
I'm using the Linux kernel 5.6.13 (5821a5593fa9f28eb6fcc95c35d00454d9bb8624)

Is it an expected behavior? or a BUG? Has anyone else faced the same issue?

Can you please suggest, what would be a good way to measure execution
time for page allocation (if not ktime_get)

Stay Safe!
Best Regards,
Shivank Garg
Open-Source Enthusiast and Student, IIT Kanpur