Messages in this thread | | | Subject | Re: [RFC PATCH kernel] Revert "net/mlx4_core: Set UAR page size to 4KB regardless of system page size" | From | Alexey Kardashevskiy <> | Date | Wed, 16 Mar 2016 16:49:00 +1100 |
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On 03/16/2016 04:10 PM, Eli Cohen wrote: > On Wed, Mar 16, 2016 at 01:07:58PM +1100, Alexey Kardashevskiy wrote: >> >> So with v4.5 as a host, there is no actual distro available today to >> use as a guest in the next 6 months (or whatever it takes to >> backport this partucular patch back there). >> >> You could have added a module parameter to enforce the old behavoir, >> at least... >> >> And sorry but from the original commit log I could not understand >> why exactly all existing guests need to be broken. Could you please >> point me to a piece of documentation describing all this UAR >> bisuness (what is UAR, why 128 UARs are required and for what, etc). >> Thanks. >> > > We are going to send a patch that fixes this using a module parameter. > The patch will be on top of Huy's patch. > > Some background to the problem: mlx4 supported devices require 128 UAR
What does UAR stand for?
> pages from PCI memory space defined by BAR2-3. Each UAR page can be > any power of 2 value from 4K up to 64K. Before Huy's patch the driver > chose UAR page size to be equal to system page size. Since PowerPC's > page size is 64K this means minimum requirement of UAR pages is not > met (default UAR BAR is 8MB and only half of it is really reserved for > UARs).
And what was the downside? afaict the performance was good...
> More details can be found in the programmer's manual.
Can you please point me to this manual on the website? I tried, honestly, could not find it. Thanks.
-- Alexey
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