Date: Fri, 24 Aug 2001 09:43:17 -0500 (CDT) From: mark tinguely <tinguely@web.cs.ndsu.nodak.edu> To: bright@mu.org, tobez@tobez.org Cc: hackers@FreeBSD.ORG Subject: Re: VM statistics per process? Message-ID: <200108241443.f7OEhHm10518@web.cs.ndsu.nodak.edu> In-Reply-To: <20010822205238.A15301@heechee.tobez.org>
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> Worse, pmap_pid_dump() is undocumented, and I don't
> understand what for(i=0;i<1024;i++) for(j=0;j<1024;j++) {} loop there is
> supposed to do... :-(
>
> I'd appreciate if someone would explain this to me.
the process' virtual memory is mapped into physical memory with page
directory table entries that point to a page table entry that points
to physical memory. there are 1024 (4096 character buffer with 4 bytes
per physical address) in both the PDE and PTEs. So 1 PDE is a pointer
to 1024 PTE which point to 1024 4KB of physical memory.
the outer for loop get a reference to the page table. the inner loop
gets the physical pages mapped to the virtual address.
the commentary for the pmap_pid_dump(int pid) routine:
for each process
if valid vmspace
get process physical memory mapping
for each physical memory page directory entry
if page directory entry exists and is currently valid
for each physical meory page table entry
if the virtual address is now into the kernel space
exit the routine
end of if the virtual address is now into the kernel space
if page table entry exists and is valid
get the vm_page associated with this physical page
print out the information about virtual and physical address
stats and pretting printing stuff
end of if page table entry exists and is valid
end of for each physical meory page table entry
end of for each physical memory page directory entry
end of if valid vmspace
end of for each process
return stats of number of physical pages used in user space for all processes
Note: most/many of the PDE and PTE entries will be not mapped or invalid.
:wq
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