Re: [PATCH v2] KVM: x86: avoid unnecessary bitmap allocation when memslot is clean

[Avi Kivity <avi@redhat.com>]

On 04/28/2010 12:50 PM, Takuya Yoshikawa wrote:
> Hi Marcelo, Avi,
>
> I updated the patch as follows.
>
> Changelog:
>   1. Inserted one "r = -ENOMEM;" line following Avi's advice.
>   2. Little change of explanation about performance improvements.
>
> I'm now testing and cleaning up my next patch series based on this,
> so please apply this if this makes sense and has no problems.
>
> Thanks,
>    Takuya
>
> ===
>
> Although we always allocate a new dirty bitmap in x86's get_dirty_log(),
> it is only used as a zero-source of copy_to_user() and freed right after
> that when memslot is clean. This patch uses clear_user() instead of doing
> this unnecessary zero-source allocation.
>
> Performance improvement: as we can expect easily, the time needed to
> allocate a bitmap is completely reduced. In my test, the improved ioctl
> was about 4 to 10 times faster than the original one for clean slots.
> Furthermore, reducing memory allocations and copies will produce good
> effects to caches too.
>
>    

Applied, thanks.

-- 
error compiling committee.c: too many arguments to function