Re: [RFT] malloc: reduce largebin granularity to reduce fragmentation

[Florian Weimer <fweimer@redhat.com>]

* Eric Wong:

> Anybody volunteers to help test and get reproducible results for
> this?  Thanks in advance.
>
> Testing and getting reproducible results is proving extremely
> expensive due to trace sizes and CPU usage required to handle
> my existing web/IMAP/NNTP-facing traffic.
>
> But the theory works in my mind and could be a solution to a
> problem I've noticed for decades at this point across long-lived
> Ruby and Perl web daemons.
>
> I'm also considering having this as a tunable and mallopt(3).
>
> And perhaps limiting the alignment to pagesize can work, because
> 20% of a large sliding mmap_threshold on 64-bit is several
> megabytes...

I looked at the patch and you did not eliminate the mostly-unused bins.
(They can still get used due to fragmentation.)  So you get a strange
conflation of various effects with this patch.  If we're serious about
this, we need to test something that reduces the bin count.  I'm not
sure if it makes senst to test this current version.

Thanks,
Florian