From: Bart Van Assche <bvanassche@acm.org>
To: I Hsin Cheng <richard120310@gmail.com>, axboe@kernel.dk
Cc: akpm@linux-foundation.org, linux-block@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] blk-wbt: Speed up integer square root in rwb_arm_timer
Date: Fri, 29 Mar 2024 11:15:38 -0700 [thread overview]
Message-ID: <848d1259-ff6e-4732-b840-a02a5e5fe2cb@acm.org> (raw)
In-Reply-To: <20240329091245.135216-1-richard120310@gmail.com>
On 3/29/24 2:12 AM, I Hsin Cheng wrote:
> As the result shown, the origin version of integer square root, which is
> "int_sqrt" takes 35.37 msec task-clock, 1,2181,3348 cycles, 1,6095,3665
> instructions, 2551,2990 branches and causes 1,0616 branch-misses.
>
> At the same time, the variant version of integer square root, which is
> "int_fastsqrt" takes 33.96 msec task-clock, 1,1645,7487 cyclces,
> 5621,0086 instructions, 321,0409 branches and causes 2407 branch-misses.
> We can clearly see that "int_fastsqrt" performs faster and better result
> so it's indeed a faster invariant of integer square root.
I'm not sure that a 4% performance improvement is sufficient to replace
the int_sqrt() implementation. Additionally, why to add a second
implementation of int_sqrt() instead of replacing the int_sqrt()
implementation in lib/math/int_sqrt.c?
> The experiments runs on x86_64 GNU/Linux Architecture and the CPU is
> Intel(R) Core(TM) i7-2600 CPU @ 3.40GHz.
Since int_sqrt() does not use divisions and since int_fastsqrt() uses
divisions, can all CPUs supported by the Linux kernel divide numbers as
quickly as the CPU mentioned above?
Thanks,
Bart.
next prev parent reply other threads:[~2024-03-29 18:15 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-29 9:12 [PATCH] blk-wbt: Speed up integer square root in rwb_arm_timer I Hsin Cheng
2024-03-29 18:15 ` Bart Van Assche [this message]
2024-03-29 19:12 ` Jens Axboe
[not found] ` <CAH5jb=btggiO7Op+k2pTS8LyjcZ0tYpvtWJRmQ8sApD-fHyHXg@mail.gmail.com>
2024-03-30 8:45 ` I Hsin Cheng
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=848d1259-ff6e-4732-b840-a02a5e5fe2cb@acm.org \
--to=bvanassche@acm.org \
--cc=akpm@linux-foundation.org \
--cc=axboe@kernel.dk \
--cc=linux-block@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=richard120310@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.