Am 2024-05-14 03:54, schrieb Ryan Libby:
That was a long winded way of saying: the "UMA bucket" axis is actually "vm phys free list order".That said, I find that dimension confusing because in fact there's just one piece of information there, the average size of a free list entry, and it doesn't actually depend on the free list order. The graph could be 2D.
It evolved into that...At first I had a 3 dimensional dataset and the first try was to plot it as is (3D). The outcome (as points) was not as good as I wanted it to be, and plotting as lines gave the wrong direction of lines. I massaged the plotting instructions until it looked good enough. I did not try a 2D plot. I agree, with different colors for each free list order a 2D plot may work too. If a 2D plot is better than a 3D plot in this case, depends on the mental model of the topic the viewer has. One size may not fit all. Feel free to experiment with other plotting styles.
The paper that defines this fragmentation index also says that "the fragmentation index is only meaningful when an allocation fails". Are you actually seeing any contiguous allocations failures in your measurements?
I'm not aware of such.The index may only be meaningful for the purposes of the goal of the paper when there are such failures, but if you look at the graph and how it changed when Bojan changed the guard pages, I see value in the graph for more than what the paper suggests.
Without that context, it seems like what the proposed sysctl reports is indirectly just the average size of free list entries. We could just report that.
The calculation of the value is part of a bigger picture. The value returned is used by some other code to make decisions.
Bye, Alexander. -- http://www.Leidinger.net alexan...@leidinger.net: PGP 0x8F31830F9F2772BF http://www.FreeBSD.org netch...@freebsd.org : PGP 0x8F31830F9F2772BF
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