Re: [PATCH v2] KVM: x86: count actual tlb flushes

["Radim Krčmář" <rkrcmar@redhat.com>]

2014-09-17 14:35-0400, Liang Chen:
> - we count KVM_REQ_TLB_FLUSH requests, not actual flushes
> (KVM can have multiple requests for one flush)
> - flushes from kvm_flush_remote_tlbs aren't counted
> - it's easy to make a direct request by mistake
> 
> Solve these by postponing the counting to kvm_check_request(),
> and refactor the code to use kvm_make_request again.
> 
> Signed-off-by: Liang Chen <liangchen.linux@gmail.com>
> ---
> Changes since v2:
> 
> * Instead of calling kvm_mmu_flush_tlb everywhere to make sure the
> stat is always incremented, postponing the counting to
> kvm_check_request.
> 
> (The idea comes from Radim. Much of the work is indeed done by him
> and is included in this patch, otherwise I couldn't start working
> on the followup work as I promised early. As I'm new to kvm
> development, please let me know if I am doing wrong here.)

I found (shame on me) Documentation/development-process/ when looking
how to help and it looks really good.
(If you read it, the rest of my mail will be obsolete :)

You usually want to Cc linux-kernel@vger.kernel.org.
(I've heard that someone actually reads it directly and it is a good
 archive otherwise.  It allows people to `git blame` your code and find
 the discussion in their preferred mail reader.)

The hard part about posting a patch is splitting it ...
You want to separate logical changes to make the code maintainable:
For this patch, I would create at least two-part series (cover letter!)

 - change the meaning of tlb_flush
 - refactor code

And see if it would make sense to split the refactoring further or if it
breaks when only a first part of the whole series is applied.

It's not a problem if your code depends on unmerged patches, you can
include someone else's code in the series as long as it isn't modified.
(Which probably is better than just mentioning that your code depends on
 some other patches from the list, but I'm not applying it ... Paolo?)