Re: CVS commit: src/sys/uvm

[yamt%mwd.biglobe.ne.jp@localhost (YAMAMOTO Takashi)]

hi,

> On Thu, Nov 25, 2010 at 04:18:25AM +0000, YAMAMOTO Takashi wrote:
>> hi,
>> 
>> > Hi, thanks for review.
>> > 
>> > On Thu, Nov 25, 2010 at 01:58:04AM +0000, YAMAMOTO Takashi wrote:
>> >> hi,
>> >> 
>> >> - what's VM_PHYSSEG_OP_PG?
>> > 
>> > It's to lookup vm_physseg by "struct vm_page *", relying on that
>> > "struct vm_page *[]" is allocated linearly.  It'll be used to remove
>> > vm_page::phys_addr as we talked some time ago.
>> 
>> i'm not sure if commiting this unused uncommented code now helps it.
>> some try-and-benchmark cycles might be necessary given that
>> vm_page <-> paddr conversion could be performace critical.
> 
> If you really care performance, we can directly pass "struct vm_page
> *" to pmap_enter().
> 
> We're doing "struct vm_page *" -> "paddr_t" just before pmap_enter(),
> then doing "paddr_t" -> "vm_physseg" reverse lookup again in
> pmap_enter() to check if a given PA is managed.  What is really
> needed here is, to lookup "struct vm_page *" -> "vm_physseg" once
> and you'll know both paddr_t and managed or not.

i agree that the current code is not ideal in that respect.
otoh, i'm not sure if passing vm_physseg around is a good idea.

YAMAMOTO Takashi

> 
>> 
>> YAMAMOTO Takashi
> 
> -- 
> Masao Uebayashi / Tombi Inc. / Tel: +81-90-9141-4635