[lttng-dev] [PATCH lttng-tools] Fix: change default UST per UID subbuffer size

[Mathieu Desnoyers]

* David Goulet (dgoulet at efficios.com) wrote:
> The default per UID subbuffer size are changed from 4096 bytes to 131072
> bytes (128k).
> 
> Fixes #524
> 
> Signed-off-by: David Goulet <dgoulet at efficios.com>
> ---
>  src/bin/lttng-sessiond/channel.c |   40 +++++++++++++++++++++++++-------------
>  src/bin/lttng-sessiond/channel.h |    3 ++-
>  src/bin/lttng-sessiond/cmd.c     |   14 ++++++++-----
>  src/common/defaults.c            |    9 ++++++---
>  src/common/defaults.h            |   25 ++++++++++++++++++------
>  src/lib/lttng-ctl/lttng-ctl.c    |    6 +++++-
>  6 files changed, 67 insertions(+), 30 deletions(-)
[...]

> diff --git a/src/common/defaults.h b/src/common/defaults.h
> index fb6a975..4606976 100644
> --- a/src/common/defaults.h
> +++ b/src/common/defaults.h
> @@ -148,7 +148,8 @@
>  /* User space defaults */
>  
>  /* Must be a power of 2 */
> -#define DEFAULT_UST_CHANNEL_SUBBUF_SIZE     4096    /* bytes */
> +#define DEFAULT_UST_PID_CHANNEL_SUBBUF_SIZE 4096    /* bytes */
> +#define DEFAULT_UST_UID_CHANNEL_SUBBUF_SIZE 131072  /* bytes */

Since we introduce DEFAULT_UST_{PID,UID}_* for SUBBUF_SIZE, I think it
would make sense to introduce PID and UID defaults for SUBBUF_NUM and
OUTPUT. They can simply map to their respective DEFAULT_UST_CHANNEL
defaults. I recommend we rename DEFAULT_UST_CHANNEL_* defaults to
_DEFAULT_UST_CHANNEL_* (leading underscore) so we ensure we don't forget
any site that uses the old macro. The code that uses those should always
use the UID/PID macros from now on. Having this in place will make it
much easier to make default value changes in the future if need be
without the risk of forgetting to changes some instances in the code
(see commit 9f778c9a8f1d65f5bfdde7cfd7294492d6fdd34c as an example of a
case we had to fix an issue that arised from inconsistency).

Moreover, I think you forgot to update the documentation (manpage +
enable-channel --help).

Thanks,

Mathieu

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com