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From: Nayna Jain <nayna@linux.vnet.ibm.com>
To: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Cc: tpmdd-devel@lists.sourceforge.net, peterhuewe@gmx.de,
	tpmdd@selhorst.net, jgunthorpe@obsidianresearch.com,
	linux-security-module@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	linux-ima-devel@lists.sourceforge.net, patrickc@us.ibm.com
Subject: Re: [PATCH v2 3/4] tpm: reduce tpm_msleep() time in get_burstcount()
Date: Fri, 15 Sep 2017 18:10:49 +0530	[thread overview]
Message-ID: <32b07575-a895-fe45-eba3-15e47adfbcac@linux.vnet.ibm.com> (raw)
In-Reply-To: <20170913010011.myvhrj2f4i3piphl@linux.intel.com>



On 09/13/2017 06:30 AM, Jarkko Sakkinen wrote:
> On Wed, Sep 06, 2017 at 08:56:38AM -0400, Nayna Jain wrote:
>> Currently, get_burstcount() function sleeps for 5msec in a loop
>> before retrying for next query to burstcount. However, if it takes
>> lesser time for TPM to return, this 5 msec delay is longer
>> than necessary.
>>
>> This patch replaces the tpm_msleep time from 5msec to 1msec.
>>
>> After this change, performance on a TPM 1.2 with an 8 byte
>> burstcount for 1000 extends improved from ~10sec to ~9sec.
>>
>> Signed-off-by: Nayna Jain <nayna@linux.vnet.ibm.com>
>> Acked-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
>> ---
>>   drivers/char/tpm/tpm_tis_core.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
>> index d1eab29cb447..d710bbc4608b 100644
>> --- a/drivers/char/tpm/tpm_tis_core.c
>> +++ b/drivers/char/tpm/tpm_tis_core.c
>> @@ -169,7 +169,7 @@ static int get_burstcount(struct tpm_chip *chip)
>>   		burstcnt = (value >> 8) & 0xFFFF;
>>   		if (burstcnt)
>>   			return burstcnt;
>> -		tpm_msleep(TPM_TIMEOUT);
>> +		tpm_msleep(1);
>>   	} while (time_before(jiffies, stop));
>>   	return -EBUSY;
>>   }
>> -- 
>> 2.13.3
> How did you pick 1 ms delay? Should there be a constant defining it?

As per ddwg input, the command may not take more than a few
microseconds. The minimum tpm_msleep() value is 1 msec, so we really
don't have a choice.  (We're working on a patch set to lower this
value even more.)

Thanks & Regards,
     - Nayna

>
> /Jarkko
>


  reply	other threads:[~2017-09-15 12:40 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-09-06 12:56 [PATCH v2 0/4] additional TPM performance improvements Nayna Jain
2017-09-06 12:56 ` [PATCH v2 3/4] tpm: reduce tpm_msleep() time in get_burstcount() Nayna Jain
2017-09-13  1:00   ` Jarkko Sakkinen
2017-09-15 12:40     ` Nayna Jain [this message]
     [not found] ` <20170906125643.5070-1-nayna-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
2017-09-06 12:56   ` [PATCH v2 1/4] tpm: ignore burstcount to improve tpm_tis send() performance Nayna Jain
2017-09-06 16:12     ` Jason Gunthorpe
2017-09-13 18:52       ` [tpmdd-devel] " Ken Goldman
     [not found]         ` <3c418974-a4c7-518e-b218-f6373c10209e-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
2017-09-13 19:01           ` Peter Huewe
2017-09-13  0:45     ` Jarkko Sakkinen
     [not found]       ` <20170912222010.ltm76m5vy2kupydi-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2017-09-13 18:39         ` Peter Huewe
2017-09-13 23:10           ` Jarkko Sakkinen
2017-09-15 12:29             ` Nayna Jain
2017-09-15 15:19               ` Jarkko Sakkinen
2017-09-06 12:56   ` [PATCH v2 2/4] tpm: define __wait_for_tpm_stat to specify variable polling sleep time Nayna Jain
2017-09-13  0:58     ` Jarkko Sakkinen
2017-09-15 12:37       ` Nayna Jain
2017-09-15 15:20         ` Jarkko Sakkinen
2017-09-06 12:56   ` [PATCH v2 4/4] tpm: use tpm_msleep() value as max delay Nayna Jain
2017-09-13  0:47     ` Jarkko Sakkinen
2017-09-14  9:25       ` Nayna Jain
2017-09-14 12:28         ` Jarkko Sakkinen
2017-09-06 12:56   ` [PATCH 2/4] tpm: define __wait_for_tpm_stat to specify variable polling sleep time Nayna Jain
2017-09-06 12:58     ` Nayna
2017-09-06 12:56 ` [PATCH 1/4] tpm: ignore burstcount to improve tpm_tis send() performance Nayna Jain
     [not found]   ` <20170906125643.5070-6-nayna-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
2017-09-06 12:58     ` Nayna
2017-09-07 16:18 ` [PATCH v2 0/4] additional TPM performance improvements Jarkko Sakkinen
2017-09-11 15:20 ` [tpmdd-devel] " Alexander.Steffen

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