Message-ID: <49185828.4090306@cosmosbay.com>
Date: Mon, 10 Nov 2008 16:50:00 +0100
From: Eric Dumazet <dada1@cosmosbay.com>
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To: Andi Kleen <andi@firstfloor.org>
CC: Robert Richter <robert.richter@amd.com>, Ingo Molnar <mingo@elte.hu>,
       LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] oprofile: re-arm APIC_DM_NMI in ppro_check_ctrs()
References: <20081107171339.GQ9785@erda.amd.com> <4917EB51.9020304@cosmosbay.com> <87ljvsott2.fsf@basil.nowhere.org> <491843C4.9090306@cosmosbay.com> <20081110154948.GW29626@one.firstfloor.org>
In-Reply-To: <20081110154948.GW29626@one.firstfloor.org>
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Andi Kleen a ?crit :
>>  			oprofile_add_sample(regs, i);
>> +			/*
>> +			 * We need to unmask the apic vector *before*
>> +			 * writing reset_value to msr counter
>> +			 */
>> +			apic_write(APIC_LVTPC, APIC_DM_NMI);
>>  			wrmsrl(msrs->counters[i].addr, -reset_value[i]);
>>  		}
>>  	}
>>  
>> -	/* Only P6 based Pentium M need to re-unmask the apic vector but it
>> -	 * doesn't hurt other P6 variant */
>> -	apic_write(APIC_LVTPC, apic_read(APIC_LVTPC) & ~APIC_LVT_MASKED);
> 
> Did you also test if it really needs to be inside the if () or 
> just before the wrmsrl? 


In my testings, the "if (CTR_OVERFLOWED())" condition is always true.

(I am profiling one event only)

I felt uncomfortable issuing the apic_write() before oprofile_add_sample()

Do you mean doing the apic_write() right at the beginning of the ppro_check_ctrs()
function ?

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