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RE: [Xen-devel] [PATCH] X86: Prefer TSC-deadline timer in Xen

To: Jan Beulich <JBeulich@xxxxxxxxxx>
Subject: RE: [Xen-devel] [PATCH] X86: Prefer TSC-deadline timer in Xen
From: "Wei, Gang" <gang.wei@xxxxxxxxx>
Date: Thu, 28 Oct 2010 23:05:22 +0800
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Cc: "Brown, Len" <len.brown@xxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Keir Fraser <keir.fraser@xxxxxxxxxxxxx>, "Wei, Gang" <gang.wei@xxxxxxxxx>
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Thread-topic: [Xen-devel] [PATCH] X86: Prefer TSC-deadline timer in Xen
>Jan Beulich [mailto:JBeulich@xxxxxxxxxx], October 28, 2010 10:36 PM
> >>> On 28.10.10 at 16:17, "Wei, Gang" <gang.wei@xxxxxxxxx> wrote:
> > +static int tdt_enabled __read_mostly;
> > +static int tdt_enable __read_mostly = 1;
> 
> I wasn't completely correct with my earlier statement regarding these:
> tdt_enable really should be __initdata, as it's only referenced by an
> __init function.

I decided to remove tdt_enable and just keep tdt_enabled.

> 
> >-    if ( timeout && ((expire = timeout - NOW()) > 0) )
> >-        apic_tmict = min_t(u64, (bus_scale * expire) >> 18, UINT_MAX);
> >-
> >-    apic_write(APIC_TMICT, (unsigned long)apic_tmict);
> >+    if ( tdt_enabled )
> >+    {
> >+        u64 tsc = 0;
> >+
> >+        if ( timeout )
> >+            tsc = stime2tsc(timeout);
> >+
> >+        wrmsrl(MSR_IA32_TSC_DEADLINE, tsc);
> >+
> >+        return 1;
> >+    }
> >+    else
> >+    {
> >+        if ( timeout && ((expire = timeout - NOW()) > 0) )
> >+            apic_tmict = min_t(u64, (bus_scale * expire) >> 18,
> UINT_MAX);
> >+
> >+        apic_write(APIC_TMICT, (unsigned long)apic_tmict);
> >+    }
> >
> >     return apic_tmict || !timeout;
> 
> So you still decided to keep the "else"? Without it the patch would be
> smaller and, at least to me, the function remain better readable...
> 
> But that's minor, or course, patch looks good to me regardless.

I will remove it.

Jimmy

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