Make the read of the current seq->value atomic, i.e., not needing to
acquire the global mutex when reading it. On 64-bit systems, this
incurs no overhead, and it will avoid the mutex and potentially
a system call.
For incrementing the value followed by waking up the threads, we are
still taking the mutex, so the current behavior is not changing. The
seq_read() behavior is already defined as, "Returns seq's current
sequence number (which could change immediately)". So the change
should not impact the current behavior.
Signed-off-by: Eelco Chaudron <echaudro@redhat.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>
It was deceptive for the example to imply that a seq can be declared
directly, because the API only allows for creating a new one on the heap.
Signed-off-by: Ben Pfaff <blp@ovn.org>
Acked-by: Ilya Maximets <i.maximets@samsung.com>
The PMD thread needs to keep processing RX queues in order
to achieve maximum throughput. It also needs to sweep emc
cache and quiesce which use seq_mutex. That mutex can
eventually block the PMD thread causing latency spikes and
affecting the throughput.
Since there is no requirement for running those tasks at a
specific time, this patch extend seq API to allow tentative
locking instead.
Reported-by: Karl Rister <krister@redhat.com>
Co-authored-by: Karl Rister <krister@redhat.com>
Signed-off-by: Flavio Leitner <fbl@redhat.com>
Signed-off-by: Daniele Di Proietto <diproiettod@vmware.com>
This attempts to prevent namespace collisions with other list libraries
Signed-off-by: Ben Warren <ben@skyportsystems.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>
struct list is a common name and can't be used in public headers.
Signed-off-by: Thomas Graf <tgraf@noironetworks.com>
Acked-by: Ben Pfaff <blp@nicira.com>
Seq objects would be really hard to use if they did not provide
acquire-release semantics. Currently they do that via
ovs_mutex_lock()/ovs_mutex_unlock(), respectively. Document the
behavior so that it is safer to rely on that elsewhere.
Signed-off-by: Jarno Rajahalme <jrajahalme@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>
The poll_loop code has a feature that, when turned on manually or
automatically (due to high CPU use), logs the source file and line number
of the code that caused a thread to wake up from poll(). Until now, when
a function calls seq_wait(), the source file and line number logged was
the code inside seq_wait(). seq_wait() has many callers, so that
information is not as useful as it could be. This commit changes the
source file and line number used to be that of seq_wait()'s caller.
I found this useful for debugging.
Signed-off-by: Ben Pfaff <blp@nicira.com>
