Re: Graph of the FreeBSD memory fragmentation

Am 2024-05-08 18:45, schrieb Bojan Novković:
> Hi,
> 
> On 5/7/24 14:02, Alexander Leidinger wrote:
> 
>> Hi,
>> 
>> I created some graphs of the memory fragmentation.
>> https://www.leidinger.net/blog/2024/05/07/plotting-the-freebsd-memory-fragmentation/
>> 
>> My goal was not comparing a specific change on a given benchmark, but 
>> to "have something which visualizes memory fragmentation". As part of 
>> that, Bojans commit 
>> https://cgit.freebsd.org/src/commit/?id=7a79d066976149349ecb90240d02eed0c4268737 
>> was just in the middle of my data collection. I have the impression 
>> that it made a positive difference in my non deterministic workload.
> Thank you for working on this, the plots look great!
> They provide a really clean visual overview of what's happening.
> I'm working on another type of memory visualization which might 
> interest you, I'll share it with you once its done.
> One small nit - the fragmentation index does not quantify fragmentation 
> for UMA buckets, but for page allocator freelists.

Do I get it more correctly now: UMA buckets are type/structure specific 
allocation lists, and the page allocator freelists are size-specific 
allocation lists (which are used by UMA when no free item is available 
in a bucket)?

>> Is there anything which prevents https://reviews.freebsd.org/D40575 to 
>> be committed?
> D40575 is closely tied to the compaction patch (D40772) which is 
> currently on hold until another issue is solved (see D45046 and related 
> revisions for more details).

Any idea about https://reviews.freebsd.org/D16620 ? Is D45046 supposed 
to replace this, or is it about something else?
I wanted to try D16620, but it doesn't apply and my naive/mechanical way 
of applying it panics.

> I didn't consider landing D40575 because of that, but I guess it could 
> be useful on its own.

It at least gives a way to quantify with numbers resp. qualitatively 
visualize. And as such it may help in visualizing differences like with 
your guard-pages commit. I wonder if the segregation of nofree 
allocations may result in a similar improvement for long-running 
systems.

Bye,
Alexander.

-- 
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http://www.FreeBSD.org    netchild@FreeBSD.org  : PGP 0x8F31830F9F2772BF