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authorDaniel Bristot de Oliveira <bristot@kernel.org>2022-05-10 11:45:23 +0200
committerSteven Rostedt (Google) <rostedt@goodmis.org>2022-05-26 21:13:00 -0400
commitaa748949b4e665f473bc5abdc5f66029cb5f5522 (patch)
treea5cd6b1b9dbb3b3307b488f5c4d133cbf2192584 /Documentation/trace
parent43994049180704fd1faf78623fabd9a5cd443708 (diff)
tracing/timerlat: Notify IRQ new max latency only if stop tracing is set
Currently, the notification of a new max latency is sent from timerlat's IRQ handler anytime a new max latency is found. While this behavior is not wrong, the send IPI overhead itself will increase the thread latency and that is not the desired effect (tracing overhead). Moreover, the thread will notify a new max latency again because the thread latency as it is always higher than the IRQ latency that woke it up. The only case in which it is helpful to notify a new max latency from IRQ is when stop tracing (for the IRQ) is set, as in this case, the thread will not be dispatched. Notify a new max latency from the IRQ handler only if stop tracing is set for the IRQ handler. Link: https://lkml.kernel.org/r/2c2d9a56c0886c8402ba320de32856cbbb10c2bb.1652175637.git.bristot@kernel.org Cc: Juri Lelli <juri.lelli@redhat.com> Cc: Ingo Molnar <mingo@redhat.com> Reported-by: Clark Williams <williams@redhat.com> Fixes: a955d7eac177 ("trace: Add timerlat tracer") Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
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