Re: UMA cache back pressure

On Mon, Nov 18, 2013 at 10:20 AM, Alexander Motin <mav_at_freebsd.org> wrote:

> On 18.11.2013 10:41, Adrian Chadd wrote:
>
>> Your patch does three things:
>>
>> * adds a couple new buckets;
>>
>
> These new buckets make bucket size self-tuning more soft and precise.
> Without them there are buckets for 1, 5, 13, 29, ... items. While at bigger
> sizes difference about 2x is fine, at smallest ones it is 5x and 2.6x
> respectively. New buckets make that line look like 1, 3, 5, 9, 13, 29,
> reducing jumps between steps, making algorithm work softer, allocating and
> freeing memory in better fitting chunks. Otherwise there is quite a big gap
> between allocating 128K and 5x128K of RAM at once.
>
>
just curious (and i do not understand whether the "1, 5 ..." are object
sizes in bytes or what), would it make sense to add some instrumentation
code (a small array of counters i presume) to track the actual number
of requests for exact object sizes, and perhaps at runtime create buckets
trying to reduce waste ?
Following your reasoning there seems to be still a big gap between
some of the numbers you quote in the sequence.

cheers
luigi