Re: [PATCH 3/6] KVM MMU: optimize/cleanup for marking parent unsync

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 




Marcelo Tosatti wrote:

>>> I'd prefer to not touch it.
>> This patch avoids walk all parents and i think this overload is really unnecessary.
>> It has other tricks in this codepath but i not noticed? :-)
> 
> My point is that there is no point in optimizing something unless its
> performance sensitive.

Hi Marcelo,

I think optimizing not only means 'performance' but also means 'smaller code'(maybe 'cleanup'
is more suitable) and 'logic optimize'(do little things), i'm not sure this patch whether can
improve system performance obviously but it optimize the code logic and reduce code size, and
it not harm other code and system performance, right? :-)

Actually, the origin code has a bug, the code segment in mmu_parent_walk():

|	if (!sp->multimapped && sp->parent_pte) {
|		......
|		return;
|	}
|	hlist_for_each_entry(pte_chain, node, &sp->parent_ptes, link)
|		for (i = 0; i < NR_PTE_CHAIN_ENTRIES; ++i) {
|			......
|		}

So, if sp->parent_pte == NULL, it's unsafe...

> And as i recall, mmu_unsync_walk was much more
> sensitive performance wise than parent walking. Actually, gfn_to_memslot 
> seems more important since its also noticeable on EPT/NPT hosts.

Yeah, i also noticed these and i'm looking into these code.

Thanks,
Xiao
--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html

[Index of Archives]     [KVM ARM]     [KVM ia64]     [KVM ppc]     [Virtualization Tools]     [Spice Development]     [Libvirt]     [Libvirt Users]     [Linux USB Devel]     [Linux Audio Users]     [Yosemite Questions]     [Linux Kernel]     [Linux SCSI]     [XFree86]
  Powered by Linux