Re: [PATCH] net: udp: add socket option to report RX queue level

2017-03-27 Thread Chris Kuiper 
Sorry, I have been transferring jobs and had no time to look at this.

Josh Hunt's change seems to solve a different problem. I was looking
for something that works the same way as SO_RXQ_OVERFL, providing
information as ancillary data to the recvmsg() call. The problem with
SO_RXQ_OVERFL alone is that it tells you when things have already gone
wrong (you dropped data), so the new option SO_RX_ALLOC acts as a
leading indicator to check if you are getting close to hitting such
problem.

Regarding only UDP being supported, it is only meaningful for UDP. TCP
doesn't drop data and if its buffer gets full it just stops the sender
from sending more. The buffer level in that case doesn't even tell you
the whole picture, since it doesn't include any information on how
much additional buffering is done at the sender side.

In terms of "a lot overhead", logically the overhead of adding
additional getsockopt() calls after each recvmsg() is significantly
larger than just getting the information as part of recvmsg(). If you
don't need it, then don't enable this option. Admitted you can reduce
the frequency of calling getsockopt() relative to recvmsg(), but that
also increases your risk of missing the point where data is dropped.

-Chris


On Fri, Mar 17, 2017 at 3:01 PM, Eric Dumazet <eric.duma...@gmail.com> wrote:
> On Fri, 2017-03-17 at 14:13 -0700, Chris Kuiper wrote:
>> This adds a new socket option "SO_RXQ_ALLOC" that enables providing
>> the RX queue buffer allocation as ancillary data from the recvmsg()
>> system call. The value reported is a byte number and together with
>> the RX queue size (obtained via getsockopt(SO_RCVBUF) can be used to
>> calculate a percentage value on how full the socket buffer is.
>> ---
>
> Seems a lot of overhead, and only UDP would be supported.
>
> I very much prefer Josh Hunt proposal
> ( https://patchwork.ozlabs.org/patch/738250/ )
>
> Ie using a separate getsockopt() call instead of adding code to UDP fast
> path ?
>
>
>

[PATCH] net: udp: add socket option to report RX queue level

2017-03-17 Thread Chris Kuiper 
This adds a new socket option "SO_RXQ_ALLOC" that enables providing
the RX queue buffer allocation as ancillary data from the recvmsg()
system call. The value reported is a byte number and together with
the RX queue size (obtained via getsockopt(SO_RCVBUF) can be used to
calculate a percentage value on how full the socket buffer is.
---
 arch/alpha/include/uapi/asm/socket.h   |  2 ++
 arch/avr32/include/uapi/asm/socket.h   |  2 ++
 arch/frv/include/uapi/asm/socket.h |  3 ++-
 arch/ia64/include/uapi/asm/socket.h|  2 ++
 arch/m32r/include/uapi/asm/socket.h|  2 ++
 arch/mips/include/uapi/asm/socket.h|  2 ++
 arch/mn10300/include/uapi/asm/socket.h |  2 ++
 arch/parisc/include/uapi/asm/socket.h  |  2 ++
 arch/powerpc/include/uapi/asm/socket.h |  2 ++
 arch/s390/include/uapi/asm/socket.h|  2 ++
 arch/sparc/include/uapi/asm/socket.h   |  2 ++
 arch/xtensa/include/uapi/asm/socket.h  |  2 ++
 include/net/sock.h |  9 +
 include/uapi/asm-generic/socket.h  |  2 ++
 net/core/sock.c|  8 
 net/ipv4/udp.c |  1 +
 net/ipv6/udp.c |  1 +
 net/socket.c   | 12 
 18 files changed, 57 insertions(+), 1 deletion(-)

diff --git a/arch/alpha/include/uapi/asm/socket.h 
b/arch/alpha/include/uapi/asm/socket.h
index afc901b7a6f6..f6e945dccdc7 100644
--- a/arch/alpha/include/uapi/asm/socket.h
+++ b/arch/alpha/include/uapi/asm/socket.h
@@ -99,4 +99,6 @@
 
 #define SCM_TIMESTAMPING_OPT_STATS 54
 
+#define SO_RXQ_ALLOC   55
+
 #endif /* _UAPI_ASM_SOCKET_H */
diff --git a/arch/avr32/include/uapi/asm/socket.h 
b/arch/avr32/include/uapi/asm/socket.h
index 5a650426f357..b1023265a58e 100644
--- a/arch/avr32/include/uapi/asm/socket.h
+++ b/arch/avr32/include/uapi/asm/socket.h
@@ -92,4 +92,6 @@
 
 #define SCM_TIMESTAMPING_OPT_STATS 54
 
+#define SO_RXQ_ALLOC   55
+
 #endif /* _UAPI__ASM_AVR32_SOCKET_H */
diff --git a/arch/frv/include/uapi/asm/socket.h 
b/arch/frv/include/uapi/asm/socket.h
index 81e03530ed39..136b6eb01801 100644
--- a/arch/frv/include/uapi/asm/socket.h
+++ b/arch/frv/include/uapi/asm/socket.h
@@ -92,5 +92,6 @@
 
 #define SCM_TIMESTAMPING_OPT_STATS 54
 
-#endif /* _ASM_SOCKET_H */
+#define SO_RXQ_ALLOC   55
 
+#endif /* _ASM_SOCKET_H */
diff --git a/arch/ia64/include/uapi/asm/socket.h 
b/arch/ia64/include/uapi/asm/socket.h
index 57feb0c1f7d7..b0b39ef019cf 100644
--- a/arch/ia64/include/uapi/asm/socket.h
+++ b/arch/ia64/include/uapi/asm/socket.h
@@ -101,4 +101,6 @@
 
 #define SCM_TIMESTAMPING_OPT_STATS 54
 
+#define SO_RXQ_ALLOC   55
+
 #endif /* _ASM_IA64_SOCKET_H */
diff --git a/arch/m32r/include/uapi/asm/socket.h 
b/arch/m32r/include/uapi/asm/socket.h
index 5853f8e92c20..f70966ea464e 100644
--- a/arch/m32r/include/uapi/asm/socket.h
+++ b/arch/m32r/include/uapi/asm/socket.h
@@ -92,4 +92,6 @@
 
 #define SCM_TIMESTAMPING_OPT_STATS 54
 
+#define SO_RXQ_ALLOC   55
+
 #endif /* _ASM_M32R_SOCKET_H */
diff --git a/arch/mips/include/uapi/asm/socket.h 
b/arch/mips/include/uapi/asm/socket.h
index 566ecdcb5b4b..03932e896273 100644
--- a/arch/mips/include/uapi/asm/socket.h
+++ b/arch/mips/include/uapi/asm/socket.h
@@ -110,4 +110,6 @@
 
 #define SCM_TIMESTAMPING_OPT_STATS 54
 
+#define SO_RXQ_ALLOC   55
+
 #endif /* _UAPI_ASM_SOCKET_H */
diff --git a/arch/mn10300/include/uapi/asm/socket.h 
b/arch/mn10300/include/uapi/asm/socket.h
index 0e12527c4b0e..d7b8dc2f454b 100644
--- a/arch/mn10300/include/uapi/asm/socket.h
+++ b/arch/mn10300/include/uapi/asm/socket.h
@@ -92,4 +92,6 @@
 
 #define SCM_TIMESTAMPING_OPT_STATS 54
 
+#define SO_RXQ_ALLOC   55
+
 #endif /* _ASM_SOCKET_H */
diff --git a/arch/parisc/include/uapi/asm/socket.h 
b/arch/parisc/include/uapi/asm/socket.h
index 7a109b73ddf7..9062b32b828d 100644
--- a/arch/parisc/include/uapi/asm/socket.h
+++ b/arch/parisc/include/uapi/asm/socket.h
@@ -91,4 +91,6 @@
 
 #define SCM_TIMESTAMPING_OPT_STATS 0x402F
 
+#define SO_RXQ_ALLOC   0x4030
+
 #endif /* _UAPI_ASM_SOCKET_H */
diff --git a/arch/powerpc/include/uapi/asm/socket.h 
b/arch/powerpc/include/uapi/asm/socket.h
index 44583a52f882..6971a55b3b2f 100644
--- a/arch/powerpc/include/uapi/asm/socket.h
+++ b/arch/powerpc/include/uapi/asm/socket.h
@@ -99,4 +99,6 @@
 
 #define SCM_TIMESTAMPING_OPT_STATS 54
 
+#define SO_RXQ_ALLOC   55
+
 #endif /* _ASM_POWERPC_SOCKET_H */
diff --git a/arch/s390/include/uapi/asm/socket.h 
b/arch/s390/include/uapi/asm/socket.h
index b24a64cbfeb1..30c7b63e3ed6 100644
--- a/arch/s390/include/uapi/asm/socket.h
+++ b/arch/s390/include/uapi/asm/socket.h
@@ -98,4 +98,6 @@
 
 #define SCM_TIMESTAMPING_OPT_STATS 54
 
+#define SO_RXQ_ALLOC   55
+
 #endif /* _ASM_SOCKET_H */
diff --git a/arch/sparc/include/uapi/asm/socket.h 
b/arch/sparc/include/uapi/asm/socket.h
index a25dc32f5d6a..f1d1fb318be0 100644
--- a/arch/sparc/include/uapi/asm/socket.h
+++