Monitoring and Tuning the Linux Networking Stack: Receiving Data

Monitoring and Tuning the Linux Networking Stack: Receiving Data(blog.packagecloud.io)

144 points by lindvall 9 years ago | 9 comments

kelleyk 9 years ago |

A nice overview; thanks for sharing it!

I don't think that your claim that GRO is "a software implementation of a hardware optimization that is known as Large Receive Offloading (LRO)" is correct, though. GRO effectively replaces LRO [1]; it has fewer limitations (it works with non-TCP traffic and with bridging [2], for example). Drivers need to support it, but they are free to take advantage of hardware offloading/acceleration, and many do (including e.g. the ixgbe driver [3]).

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[1] In terms of function, and in the sense that LRO could be removed if the drivers that were using LRO were updated to use GRO instead.

[2] Relevant bug: https://bugzilla.redhat.com/show_bug.cgi?id=772317

[3] Which actually supports both LRO and GRO; if I recall, in older versions, bad things(tm) would sometimes happen if you had both enabled at the same time (whereas now the LRO setting is ignored if GRO is enabled).

poorman 9 years ago |

While most of this can be found in the MAN pages, this is a nice synopsis to have on hand. Definitely going to bookmark this.

snvzz 9 years ago |

> There is, unfortunately, no easy way out.

Disagree. BSD.

feld 9 years ago | |

That's a tough pill to swallow for many

brobinson 9 years ago | |

There's also kernel bypass setups which seem to be common when crazy performance is required.

varlock 9 years ago |

It is a bit hard to follow the listings as they don't use a monospaced font. A part from that, very detailed and useful article.

jcapote 9 years ago | |

Sorry about that! What browser/operating system? I suspect this is a missing font issue.

mscdex 9 years ago | | |

I think I see the same thing on Chrome/Linux. If I comment out the `font-family: monaco` rule in the `article.type-system-sans code` CSS rule, then a monospace font is used and makes things much more readable.