[RFC] Support dynamically loading LTTng tracing #1621
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added 4 commits
July 2, 2025 20:12
Currently static compilation with LTTng tracing enabled fails with
the following errors:
In file included from /home/rdma-core/providers/rxe/rxe_trace.c:9:
/rdma-core/providers/rxe/rxe_trace.h:12:38: fatal error: rxe_trace.h: No such file or directory
12 | #define LTTNG_UST_TRACEPOINT_INCLUDE "rxe_trace.h"
| ^~~~~~~~~~~~~
compilation terminated.
make[2]: *** [providers/rxe/CMakeFiles/rxe.dir/build.make:76: providers/rxe/CMakeFiles/rxe.dir/rxe_trace.c.o] Error 1
make[2]: *** Waiting for unfinished jobs....
In file included from /home/rdma-core/providers/efa/efa_trace.c:9:
/home/rdma-core/providers/efa/efa_trace.h:12:38: fatal error: efa_trace.h: No such file or directory
12 | #define LTTNG_UST_TRACEPOINT_INCLUDE "efa_trace.h"
| ^~~~~~~~~~~~~
compilation terminated.
make[2]: *** [providers/efa/CMakeFiles/efa-static.dir/build.make:76: providers/efa/CMakeFiles/efa-static.dir/efa_trace.c.o] Error 1
make[1]: *** [CMakeFiles/Makefile2:3085: providers/efa/CMakeFiles/efa-static.dir/all] Error 2
make[1]: *** Waiting for unfinished jobs....
In file included from /home/rdma-core/providers/mlx5/mlx5_trace.c:9:
/home/rdma-core/providers/mlx5/mlx5_trace.h:12:38: fatal error: mlx5_trace.h: No such file or directory
12 | #define LTTNG_UST_TRACEPOINT_INCLUDE "mlx5_trace.h"
| ^~~~~~~~~~~~~~
compilation terminated.
make[2]: *** [providers/mlx5/CMakeFiles/mlx5-static.dir/build.make:76: providers/mlx5/CMakeFiles/mlx5-static.dir/mlx5_trace.c.o] Error 1
make[2]: *** Waiting for unfinished jobs....
In file included from /home/rdma-core/providers/hns/hns_roce_u_trace.c:9:
/home/rdma-core/providers/hns/hns_roce_u_trace.h:12:38: fatal error: hns_roce_u_trace.h: No such file or directory
12 | #define LTTNG_UST_TRACEPOINT_INCLUDE "hns_roce_u_trace.h"
| ^~~~~~~~~~~~~~~~~~~~
compilation terminated.
Fix it by linking the library and including drivers' directories for
static compilation.
Fixes: 382b359 ("efa: Add support for LTTng tracing")
Signed-off-by: wenglianfa <wenglianfa@huawei.com>
Signed-off-by: Junxian Huang <huangjunxian6@hisilicon.com>
Create extra provider libraries for tracing so that the regular libraries does not need to have a dependency on LTTng. For example, there will be a new libhns_trace-rdmav*.so for hns tracing. Usage example: $ lttng create my_session $ lttng enable-event -u rdma_core_hns:post_send $ lttng start $ LD_PRELOAD=/usr/lib64/libibverbs/libhns_trace-rdmav*.so ib_send_bw -d hns_0 $ LD_PRELOAD=/usr/lib64/libibverbs/libhns_trace-rdmav*.so ib_send_bw -d hns_0 10.10.10.10 $ lttng stop $ lttng view No additional dependencies or performance penalty will be introduced if users don't load the tracing library explicitly as shown above. This change involves all providers that support LTTng tracing, including efa, hns, mlx5 and rxe. Signed-off-by: wenglianfa <wenglianfa@huawei.com> Signed-off-by: Junxian Huang <huangjunxian6@hisilicon.com>
Define rdma_tracepoint() in the common trace.h to remove duplicate definition in drivers. Signed-off-by: wenglianfa <wenglianfa@huawei.com> Signed-off-by: Junxian Huang <huangjunxian6@hisilicon.com>
Now that tracing libraries has been separated from regular providers libraries, enabling LTTng tracing by default has become feasible for release version rdma-core. Users can customize the installation of the tracing libraries according to their needs, improving the usability. Signed-off-by: wenglianfa <wenglianfa@huawei.com> Signed-off-by: Junxian Huang <huangjunxian6@hisilicon.com>
|
And I still think that providing extra, special tracing libraries as part of rdma-core is wrong approach. |
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This PR is an RFC to support dynamically loading LTTng tracing.
As mentioned in our brief discussion previously in #1587, there are some benefits to supporting this:
We believe that this can greatly improve the usability of LTTng tracing.
BTW, the first patch is included incidentally and isn’t actually part of this feature. It’s meant to fix the static compilation failures when enabling LTTng.