diff options
| author | Arjun Roy <arjunroy@google.com> | 2020-02-15 02:30:50 +0300 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2020-02-17 06:25:02 +0300 |
| commit | 33946518d493cdf10aedb4a483f1aa41948a3dab (patch) | |
| tree | ac31781461616de8689ed71d153a29ae8b8523ee /include | |
| parent | c8856c051454909e5059df4e81c77b9c366c5515 (diff) | |
| download | linux-33946518d493cdf10aedb4a483f1aa41948a3dab.tar.xz | |
tcp-zerocopy: Return sk_err (if set) along with tcp receive zerocopy.
This patchset is intended to reduce the number of extra system calls
imposed by TCP receive zerocopy. For ping-pong RPC style workloads,
this patchset has demonstrated a system call reduction of about 30%
when coupled with userspace changes.
For applications using epoll, returning sk_err along with the result
of tcp receive zerocopy could remove the need to call
recvmsg()=-EAGAIN after a spurious wakeup.
Consider a multi-threaded application using epoll. A thread may awaken
with EPOLLIN but another thread may already be reading. The
spuriously-awoken thread does not necessarily know that another thread
'won'; rather, it may be possible that it was woken up due to the
presence of an error if there is no data. A zerocopy read receiving 0
bytes thus would need to be followed up by recvmsg to be sure.
Instead, we return sk_err directly with zerocopy, so the application
can avoid this extra system call.
Signed-off-by: Arjun Roy <arjunroy@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include')
| -rw-r--r-- | include/uapi/linux/tcp.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h index 548f480b9c66..1a7fc856e237 100644 --- a/include/uapi/linux/tcp.h +++ b/include/uapi/linux/tcp.h @@ -346,5 +346,6 @@ struct tcp_zerocopy_receive { __u32 length; /* in/out: number of bytes to map/mapped */ __u32 recv_skip_hint; /* out: amount of bytes to skip */ __u32 inq; /* out: amount of bytes in read queue */ + __s32 err; /* out: socket error */ }; #endif /* _UAPI_LINUX_TCP_H */ |