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
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