svn commit: r279539 - head/sys/sys

[Julian Elischer]

On 3/2/15 4:55 PM, Neel Natu wrote:
> Hi Davide,
>
> On Mon, Mar 2, 2015 at 12:26 PM, Davide Italiano <davide at freebsd.org> wrote:
>> On Mon, Mar 2, 2015 at 12:05 PM, John-Mark Gurney <jmg at freebsd.org> wrote:
>>> Author: jmg
>>> Date: Mon Mar  2 20:05:16 2015
>>> New Revision: 279539
>>> URL: https://svnweb.freebsd.org/changeset/base/279539
>>>
>>> Log:
>>>    give others fair warning that _SPARE2 isn't just cxgb, but used by large
>>>    number of other subsystems, so you probably don't want _SPARE2..
>>>
>>>    ktr needs an overhaul to really only compile in the ones you want,
>>>    we've long passed the 31 bits it provides..
>>>
>> If you really want to do the overhaul (which would be honestly great),
>> I might consider revamping my work for per-cpu KTR buffer and include
>> that in the change. Originally it was just an exercise, but then it
>> evolved and I've been sitting with it in my local tree for a while. I
>> never had the chutzpah to upstream it because it involves fundamental
>> changes and breaks compatibility with the old ktrdump(1) format.
>> A rather outdated (and maybe not completely functional) version of the
>> patch can be found here:
>> http://people.freebsd.org/~davide/locking/ktr_percpu.4.diff , which
>> should give you an high level view of the change.
>> I can update it to the last version and bring up for review, if
>> somebody think it might be a sane idea avoiding synchronization on a
>> single buffer for KTR.
I think it would be  a problem...
one of the truely useful things about ktr is that it does use a single 
buffer.
this means that you get the true interaction between CPUS.
Schedgraph relies on this (as one example).

> This would be a very welcome improvement.
>
> best
> Neel
>
>> --
>> Davide
>>
>
>