Add shim for sendmmsg when sendmmsg does not exist #1896
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Some users have asked to build with glibc versions that do not have sendmmsg. This change checks for the existance of sendmmsg, and if its missing implements a shim version that has identical functionality
src/platform/datapath_epoll.c
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| while (SuccessCount < MessageLen) { | ||
| int Result = sendmsg(fd, &Messages[SuccessCount].msg_hdr, Flags); | ||
| if (Result < 0) { | ||
| return SuccessCount == 0 ? Result : (ssize_t)SuccessCount; |
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Wouldn't returning Result incorrectly set SuccessfullySentMessages in line 2592?
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No. The contract of sendmmsg is if the first message errors that return value is returned. Otherwise it returns the number of successful sends.
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I manually ran the test suite and enabled this flag. I also at the same time disabled the USO flag as well, which checks this even more. |
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Are there benchmarking data regarding the performance degradation when sendmmsg is not available? |
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We don't have current benchmarking numbers, because none of our systems support any off the offloading. However, we do have some older performance data. The red jump was adding sendmmsg. The black jump here is adding GSO, which with an older libc you also won't have. So I would expect performance to be similar to where things were before the red jump.
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Some users have asked to build with glibc versions that do not have sendmmsg. This change checks for the existance of sendmmsg, and if its missing implements a shim version that has identical functionality.
Closes #1884