Messages in this thread | | | Date | Tue, 17 Jun 2003 13:42:06 -0700 (PDT) | Subject | Re: patch for common networking error messages | From | "David S. Miller" <> |
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From: Janice Girouard <girouard@us.ibm.com> Date: Tue, 17 Jun 2003 15:40:48 -0500
From: David S. Miller" <davem@redhat.com> Date: 06/17/2003 03:27 PM
On RX, clever RX buffer management is what we need.
What RX buffer management are you proposing? I'm having a hard time understanding how you'll get rid of the copy without support from the card.
Sigh... someone write store email down somewhere for the next time someone asks about this.
The "one true way (tm)" works like this:
1) Chip has a "flow cache", LRU based, managed like routing caches in many production router implementations. Difference is that it merely does flow watching.
Flow entries are keyed on saddr/daddr/sport/dport. Flow misses kill the oldest entry, and replace it with the new one.
Entries are only created in response to full sized data packets.
2) The receive buffering is segmented into small (256 byte) and PAGE sized buffers. IP/TCP/whatever headers (determined using a simply programmable header parser logic, so you can do things like RPC etc. headers for NFS) are put into the "small" buffers, data portions for matching flows get accumulated into the PAGE sized buffers.
It is implied that the card's flow cache keeps track of the pointers into page it is currently trying to fill for that flow.
So the first time you see a flow, you add a entry and grab a page buffer and stick the data part into the page buffer and the TCP/IP/etc. headers into a "small" buffer. You defer a configurable amount of time waiting for more TCP data packets (a packet train) to accumulate more into the PAGE buffer for that flow.
Such receive buffers are presented to the stack as a linked list of packets, with some indicator that together their data parts are filling a page.
Things like "sys_receivefile()" and NFS flip these things into the filesystem page cache.
I'm surprised this isn't evident to more people... - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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