[ltt-dev] [RFC UST and LTTng] Daemon model proposal

David Goulet david.goulet at polymtl.ca
Mon Jan 31 10:15:33 EST 2011

On 11-01-28 05:36 PM, Nils Carlson wrote:
> Hi David, just one little question below...
> On Jan 28, 2011, at 9:20 PM, David Goulet wrote:
>> On 11-01-20 09:36 AM, Michel Dagenais wrote:
>>> Buffers creation - creates shared memory for the tracing buffers.
>>> --> Why is buffer creation the responsability of the sessiond?
>>> Ressource accounting, preventing abuses, is easier if the traced
>>> application via libust does the buffer creation!
>> The main reason was because the application cannot set the shared
>> memory with the read access to the tracing group. (unless the apps uid
>> is in the tracing group).
> I'm not quite with you here... Shouldn't all apps that we want to trace
> have to be in the tracing group? Or is this unreasonable...

No, it's actually the goal :). Every buffers are readable by the tracing 
group. However, it's not reasonable to have every user apps in the 
tracing group (Ex: put 'mysql' in tracing group, 'www-data', and so on).

This is why, the sessiond needs to manage the buffers.

> I think having a policy where all users who need to trace are members of
> the tracing group as are all applications that can be traced makes a lot
> of sense....

Same page :)


> /Nils

David Goulet
LTTng project, DORSAL Lab.

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