Hi, lttng-dev team
When lttng-sessiond exits, the ust applications should call
lttng_ust_objd_table_owner_cleanup() and clean up all shm resource(unmap and
close). Howerver I do find that the ust applications keep opening "all" of the
shm fds("/dev/shm/ust-shm-consumer-81132 (deleted)") and do NOT free shm.
If we run lttng-sessiond again, ust applications can get a new piece of shm
and a new list of shm fds so double shm usages. Then if we kill lttng-sessiond,
what the mostlikely happened is ust applications close the new list of shm fds
and free new shm resource but keeping old shm still. In other word, we can not
free this piece of shm unless we killing ust applications!!!
So Is there any possilbe that ust applications failed calling
lttng_ust_objd_table_owner_cleanup()? Do you have ever see this problem? Do you
have any advice to free the shm without killling ust applications(I tried to
dig into kernel shm_open and /dev/shm, but not found any ideas)?
Thanks in advance
zhenyu.ren
------------------------------------------------------------------
发件人：zhenyu.ren via lttng-dev <lttng-dev@lists.lttng.org>
发送时间：2022年2月23日(星期三) 23:09
收件人：lttng-dev <lttng-dev@lists.lttng.org>
主 题：[lttng-dev] 回复： shm leak in traced application?
>"I found these items also exist in a traced application which is a long-time
>running daemon"
Even if lttng-sessiond has been killed!!
Thanks
zhenyu.ren
------------------------------------------------------------------
发件人：zhenyu.ren via lttng-dev <lttng-dev@lists.lttng.org>
发送时间：2022年2月23日(星期三) 22:44
收件人：lttng-dev <lttng-dev@lists.lttng.org>
主 题：[lttng-dev] shm leak in traced application?
Hi,
There are many items such as "/dev/shm/ust-shm-consumer-81132 (deleted)"
exist in lttng-sessiond fd spaces. I know it is the result of shm_open() and
shm_unlnik() in create_posix_shm().
However, today, I found these items also exist in a traced application which
is a long-time running daemon. The most important thing I found is that there
seems no reliable way to release share memory.
I tried to kill lttng-sessiond but not always release share memory.
Sometimes I need to kill the traced application to free share memory....But it
is not a good idea to kill these applications.
My questions are:
1. Is there any way to release share memory without killing any traced
application?
2. Is it normal that many items such as "/dev/shm/ust-shm-consumer-81132
(deleted)" exist in the traced application?
Thanks
zhenyu.ren
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