From: Norbert Lange via lttng-dev <lttng-dev@lists.lttng.org>
To: lttng-dev <lttng-dev@lists.lttng.org>
Subject: [lttng-dev] reading context fields causes syscalls
Date: Wed, 19 May 2021 14:11:03 +0200 [thread overview]
Message-ID: <CADYdroN3=pAe66crtsVT9aHE4T+bT61-tvHFKCuwZYkHhuyFjw@mail.gmail.com> (raw)
Hello,
Several context fields will cause a syscall atleast the first time a
tracepoint is
recorded. For example all of the following:
`lttng add-context -c chan --userspace --type=vpid --type=vtid --type=procname`
Each of them seems cached in TLS however, and most should never change
after startup.
As I am using Lttng over Xenomai, syscalls are strictly forbidden, I
would like to have some function that prepares all data, which I can
call on each thread before it switches to realtime work.
Kinda similar to urcu_bp_register_thread, I'd like to have some
`lttng_ust_warmup_thread` function that fetches the context values
that can be cached. (urcu_bp_register_thread should be called there
aswell)
I considered just doing a tracepoint, but AFAIK the channel can be
changed/configured after the process is running. So this is not robust
enough.
regards, Norbert
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next reply other threads:[~2021-05-19 12:11 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-19 12:11 Norbert Lange via lttng-dev [this message]
2021-05-19 18:52 ` [lttng-dev] reading context fields causes syscalls Mathieu Desnoyers via lttng-dev
2021-05-20 12:46 ` Norbert Lange via lttng-dev
2021-05-20 13:28 ` Mathieu Desnoyers via lttng-dev
2021-05-20 13:42 ` Norbert Lange via lttng-dev
2021-05-20 14:15 ` Mathieu Desnoyers via lttng-dev
2022-07-14 13:10 ` Norbert Lange via lttng-dev
2022-07-18 15:46 ` Mathieu Desnoyers via lttng-dev
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