The page tables can be enabled/disabled on a per VMID basis, but memory
management in the core kernel works with pages.
So you need a relocation table just because of this. Additional to that
the TLB is more than big enough, so there isn't much performance gain if
you use huge pages.
Please note that the VM subsystem also supports giant pages, so if your
application manages to allocate things in chunks of at least 1GB you
only get a single page table entry for that.
Regards,
Christian.
Am 01.12.20 um 12:28 schrieb Smith John:
Hi Christian,
Thanks for your reply. I agree with you that the VMID0 is special and
remapping is important. I was not sure if different VIMDs could have
different settings, such as enable/disable page tables.
Or to put it another way, I was wondering if the hardware supports
purely physical addressing like the real mode in CPUs, or page tables
are essential for the hardware.
More specifically, assuming it supports "real mode", to copy things
from A to B, one could allocate rings which are accessible by MMIO and
fill sdma packets using physical address to transfer data.
Regards,
Smith
Christian König <[email protected]
<mailto:[email protected]>> 于2020年12月1日周二
下午5:50写道：
Am 01.12.20 um 07:58 schrieb Smith John:
Hello!
I was trying to figure out the impact of gpu page tables on
applications' performance. I noticed that there are 16 vmids
supported by the hardware /Vega 10/. Is it possible to use
physical address directly in some vmids, or use physical address
globally?
No. VMID0 is used by the kernel for jobs like copying things from
A to B and even there we use the VM remapping functionality.
Regards,
Christian.
_______________________________________________
amd-gfx mailing list
[email protected] <mailto:[email protected]>
https://lists.freedesktop.org/mailman/listinfo/amd-gfx
_______________________________________________
amd-gfx mailing list
[email protected]
https://lists.freedesktop.org/mailman/listinfo/amd-gfx
_______________________________________________
amd-gfx mailing list
[email protected]
https://lists.freedesktop.org/mailman/listinfo/amd-gfx
