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<div class="moz-cite-prefix">The page tables can be enabled/disabled
on a per VMID basis, but memory management in the core kernel
works with pages.<br>
<br>
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.<br>
<br>
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.<br>
<br>
Regards,<br>
Christian.<br>
<br>
Am 01.12.20 um 12:28 schrieb Smith John:<br>
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cite="mid:CAGztBWVOhbMnjo7vGmCAa6LPN0USK9GneWyw8LaDJPeeK_x66g@mail.gmail.com">
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<div dir="ltr"> Hi Christian,
<div>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. </div>
<div>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.</div>
<div>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.</div>
<div><br>
</div>
<div>Regards,</div>
<div>Smith</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">Christian König <<a
href="mailto:ckoenig.leichtzumerken@gmail.com"
moz-do-not-send="true">ckoenig.leichtzumerken@gmail.com</a>>
于2020年12月1日周二 下午5:50写道：<br>
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0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div>
<div>Am 01.12.20 um 07:58 schrieb Smith John:<br>
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<div dir="ltr">Hello!
<div>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 <i>Vega
10</i>. Is it possible to use physical address
directly in some vmids, or use physical address
globally?</div>
</div>
</blockquote>
<br>
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.<br>
<br>
Regards,<br>
Christian.<br>
<br>
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