From: Kuan-Wei Chiu <visitorckw@gmail.com>
To: Matthew Sakai <msakai@redhat.com>
Cc: dm-devel@lists.linux.dev, linux-kernel@vger.kernel.org,
jserv@ccns.ncku.edu.tw
Subject: Potential heapify performance issue in dm-vdo
Date: Wed, 21 May 2025 23:04:40 +0800 [thread overview]
Message-ID: <aC3riPZ6GV/dlr7Y@visitorckw-System-Product-Name> (raw)
Hi Matthew,
Recently noticed that the current heapify method in min_heap.h may
degrade performance when the heap contains many compare-equal elements,
compared to the previous version.
In detail, the new heapify reduces the number of comparisons by about
50% when all elements are distinct. However, when all elements are
equal, the comparison count can degrade from O(1) to O(log n).
I don't have enough domain knowledge of dm-vdo, so I'd like to ask
whether it uses heaps with many compare-equal elements. If so, I'll
work on fixing the issue.
Regards,
Kuan-Wei
next reply other threads:[~2025-05-21 15:04 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-05-21 15:04 Kuan-Wei Chiu [this message]
2025-05-21 18:57 ` Potential heapify performance issue in dm-vdo Matthew Sakai
2025-05-22 7:22 ` Kuan-Wei Chiu
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=aC3riPZ6GV/dlr7Y@visitorckw-System-Product-Name \
--to=visitorckw@gmail.com \
--cc=dm-devel@lists.linux.dev \
--cc=jserv@ccns.ncku.edu.tw \
--cc=linux-kernel@vger.kernel.org \
--cc=msakai@redhat.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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox