----- On Nov 13, 2017, at 1:40 PM, Nalin Pai <[email protected]> wrote:
> Hi, > In the per-pid buffer scheme, when are the ring buffers allocated for each > pid? > Is it when a channel is created or is it an event provided by that process is > enabled for a specific channel. In per-pid buffers, the buffers are allocated for each registered process whenever each of those process is registered (typically at program launch). Buffer allocation of per-pid buffers brings a significant overhead on systems with short-lived processes. Using "per-uid" buffers is recommended instead in those situations. > I am trying to understand whether there is an overhead to creating many > channels. Will a process incur the allocation of buffers for a channel that is > not interested in any of the events that the process is providing? Yes, a process will have to allocate buffers if it's registered to lttng-sessiond, even if it does not contain any event enabled for that channel. This is needed to handle dynamically loaded libraries for instance, which may add additional events into a process after its initial constructor execution. Thanks, Mathieu > -Nalin > _______________________________________________ > lttng-dev mailing list > [email protected] > https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com
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