From: Marcelo Tosatti <mtosatti@redhat.com>
To: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Cc: avi@redhat.com, mst@redhat.com, kvm@vger.kernel.org
Subject: Re: [PATCH -v4] KVM: x86: lapic: Clean up find_highest_vector() and count_vectors()
Date: Wed, 12 Sep 2012 13:39:32 -0300 [thread overview]
Message-ID: <20120912163932.GA24540@amt.cnet> (raw)
In-Reply-To: <20120905193001.99d06c26.yoshikawa.takuya@oss.ntt.co.jp>
On Wed, Sep 05, 2012 at 07:30:01PM +0900, Takuya Yoshikawa wrote:
> find_highest_vector() and count_vectors():
> - Instead of using magic values, define and use proper macros.
>
> find_highest_vector():
> - Remove likely() which is there only for historical reasons and not
> doing correct branch predictions anymore. Using such heuristics
> to optimize this function is not worth it now. Let CPUs predict
> things instead.
>
> - Stop checking word[0] separately. This was only needed for doing
> likely() optimization.
>
> - Use for loop, not while, to iterate over the register array to make
> the code clearer.
>
> Note that we actually confirmed that the likely() did wrong predictions
> by inserting debug code.
>
> Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
> Cc: Michael S. Tsirkin <mst@redhat.com>
Applied, thanks.
prev parent reply other threads:[~2012-09-12 17:05 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-24 9:15 [PATCH] KVM: x86: lapic: Fix the misuse of likely() in find_highest_vector() Takuya Yoshikawa
2012-08-27 20:25 ` Marcelo Tosatti
2012-08-28 9:57 ` Takuya Yoshikawa
2012-08-29 19:10 ` Marcelo Tosatti
2012-08-29 22:51 ` Michael S. Tsirkin
2012-08-30 1:09 ` Takuya Yoshikawa
2012-08-30 6:37 ` Michael S. Tsirkin
2012-08-30 9:50 ` Takuya Yoshikawa
2012-08-30 10:10 ` Michael S. Tsirkin
2012-08-30 10:24 ` Takuya Yoshikawa
2012-08-30 10:44 ` Michael S. Tsirkin
2012-08-30 12:30 ` [PATCH -v3] KVM: x86: lapic: Clean up find_highest_vector() and count_vectors() Takuya Yoshikawa
2012-08-30 13:21 ` Michael S. Tsirkin
2012-08-30 16:09 ` Takuya Yoshikawa
2012-08-30 16:49 ` Michael S. Tsirkin
2012-09-05 8:30 ` Takuya Yoshikawa
2012-09-05 9:26 ` Michael S. Tsirkin
2012-09-05 9:40 ` Takuya Yoshikawa
2012-09-05 9:51 ` Michael S. Tsirkin
2012-09-05 10:30 ` [PATCH -v4] " Takuya Yoshikawa
2012-09-05 10:58 ` Michael S. Tsirkin
2012-09-12 16:39 ` Marcelo Tosatti [this message]
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