Hi, Alan Cox
Thanks for your reply. I want to know why the NKPT set to 32 in
revision187465,
is it possible that set NKPT less or lager than 32? What's the limitation if
set NKPT to 32?
I also guess the KPTphys[] not used in kernel initialization on amd64 in
revision187465. And
I notice that in revision189075, in function pmap_init() the vm page array
entries for the kernel
pmap's page table pages is initialized; but in revision187458, the
initialization is not performed.
I guess the earlist part of the kernel's initialization is the
pmap_bootstrap(firstaddr),
this will call function create_pagetables().
In function create_pagetables(), we first use allocpages(firstaddr,
NKPT) to
allocate NKPT pages, then initialize the KPTphys[] and KPDphys[]. But then
the KPDphys[] re-initialize the range (0, *firstaddr) in 2MB page:
/* Map from zero to end of allocations under 2M pages */
/* This replaces some of the KPTphys entries above */
for (i = 0; (i PDRSHIFT) *firstaddr; i++) {
((pd_entry_t *)KPDphys)[i] = i PDRSHIFT;
((pd_entry_t *)KPDphys)[i] |= PG_RW | PG_V | PG_PS | PG_G;
}
This means that the KPDphys[] will be override completely if the range
(KERNBASE, virtual_avail)'s size larger than 64MB, so I guess that the
KPTphys[]
not used anymore if the range (KERNBASE, virtual_avail)'s size larger than
64MB.
在 2011年3月30日 下午11:50，Alan Cox a...@rice.edu写道：
On 03/30/2011 01:47, fuzhli wrote:
Hi, Alan
I'm study the Revision 187465 : Prepare for a larger kernel virtual
address space. After read some relative source code, I have an
question about the macro NKPT on amd64: why 32 is enough for the
kernel page table pages? Do it means that the range (KERNBASE,
virtual_avail) should always less than 64MB( 32 * 2MB)?
NKPT sets the size of the kernel page table during the earliest part of
the kernel's initialization. After that, the size of the page table
grows dynamically according to usage.
Regards,
Alan
--
别做梦,你已24岁了
___
freebsd-questions@freebsd.org mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-questions
To unsubscribe, send any mail to freebsd-questions-unsubscr...@freebsd.org
