Hi,
I've updated the driver with comments from the 1st round.
The updated webrev is at http://cr.opensolaris.org/~joostm/onnv-vr/
Below, comments on what was changed since the last webrev.
Lines 717-760: I believe you shouldn't need to use driver.conf...
Brussels is the "new" way forward, and I believe that a driver
without legacy concerns shouldn't be using driver.conf anymore.
I added it for consistancy with the current state of solaris' drivers.
Just tell me again it needs to go and it's gone.
Nuke it. I'm working on a different ethernet driver for a popular
commodity chip, and it will *not* have driver.conf settings. (Every
friggin' driver always had its own unique tunables, so there was no
consistency to follow. Brussels is the way forward.)
OK. I will remove it.
Removed. There's no vr.conf anymore.
<lengthy disscussion about copy vs dma map removed>
See my earlier comments. If you want to do this, go ahead, but I
think you're mistaken. You should do some performance analysis to see
if you're really saving cpu cycles. I suspect you might be saving as
much as you think. (It will vary by packet size, as well as specific
CPU and MMU configuration, of course.)
OK. I will re-evaluate copy versus dma mapping on the VIA C3 box
measured using NFS. Is your objection with dma mappings on the TX path,
RX path or both?
I did this re-evaluation using various tools (ttcp, netperf, vdbench)
and found that there's (indeed) no gain in using dma bind on the
TX path and even no gain in using "loan up" on the RX path.
My summary conclusion (for this driver, tested on 600Mhz VIA C3):
TX: cost of ddi_dma_addr_bind_handle() is equal to cost of mcopymsg
RX: cost of the "loan up" mechanism is equal to the cost allocb+bcopy
Thus, "loan up" is removed from the RX path and dma map is removed from
the TX path. The driver now copies the data to/from pre-mapped buffers,
which significantly simplifies the driver.
Thank you, Joost
--
Joost Mulders + email: [email protected]
Technical Specialist + phone: +31-33-45-15701
Client Solutions + fax: +31-33-45-15734
Sun Microsystems + mobile: +31-6-5198-7268
-= Anything not done right, has to be done again =-
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