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| author | Eric Dumazet <edumazet@google.com> | 2012-07-20 05:45:50 +0000 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2012-07-20 10:59:41 -0700 |
| commit | 6f458dfb409272082c9bfa412f77ff2fc21c626f (patch) | |
| tree | 7475cd12eb01023b9852cbc957080b9aa7cfdc64 /include/linux/tcp.h | |
| parent | 9dc274151a548ffd215caecec5a8872db8799447 (diff) | |
| download | lwn-6f458dfb409272082c9bfa412f77ff2fc21c626f.tar.gz lwn-6f458dfb409272082c9bfa412f77ff2fc21c626f.zip | |
tcp: improve latencies of timer triggered events
Modern TCP stack highly depends on tcp_write_timer() having a small
latency, but current implementation doesn't exactly meet the
expectations.
When a timer fires but finds the socket is owned by the user, it rearms
itself for an additional delay hoping next run will be more
successful.
tcp_write_timer() for example uses a 50ms delay for next try, and it
defeats many attempts to get predictable TCP behavior in term of
latencies.
Use the recently introduced tcp_release_cb(), so that the user owning
the socket will call various handlers right before socket release.
This will permit us to post a followup patch to address the
tcp_tso_should_defer() syndrome (some deferred packets have to wait
RTO timer to be transmitted, while cwnd should allow us to send them
sooner)
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Tom Herbert <therbert@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Cc: Nandita Dukkipati <nanditad@google.com>
Cc: H.K. Jerry Chu <hkchu@google.com>
Cc: John Heffner <johnwheffner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/linux/tcp.h')
| -rw-r--r-- | include/linux/tcp.h | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/include/linux/tcp.h b/include/linux/tcp.h index 9febfb685c33..2761856987b2 100644 --- a/include/linux/tcp.h +++ b/include/linux/tcp.h @@ -515,7 +515,9 @@ struct tcp_sock { enum tsq_flags { TSQ_THROTTLED, TSQ_QUEUED, - TSQ_OWNED, /* tcp_tasklet_func() found socket was locked */ + TCP_TSQ_DEFERRED, /* tcp_tasklet_func() found socket was owned */ + TCP_WRITE_TIMER_DEFERRED, /* tcp_write_timer() found socket was owned */ + TCP_DELACK_TIMER_DEFERRED, /* tcp_delack_timer() found socket was owned */ }; static inline struct tcp_sock *tcp_sk(const struct sock *sk) |