linux-kernel - Re: [PATCH v3 1/2] tpm: reduce poll sleep time in tpm

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Message-ID: <20180514104701.GD8228@linux.intel.com>
Date:   Mon, 14 May 2018 13:47:01 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Nayna Jain <nayna@...ux.vnet.ibm.com>
Cc:     linux-integrity@...r.kernel.org, zohar@...ux.vnet.ibm.com,
        linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, peterhuewe@....de,
        tpmdd@...horst.net, jgunthorpe@...idianresearch.com,
        patrickc@...ibm.com
Subject: Re: [PATCH v3 1/2] tpm: reduce poll sleep time in tpm_transmit()

On Mon, May 14, 2018 at 01:46:00PM +0300, Jarkko Sakkinen wrote:
> On Mon, May 07, 2018 at 12:07:32PM -0400, Nayna Jain wrote:
> > tpm_try_transmit currently checks TPM status every 5 msecs between
> > send and recv. It does so in a loop for the maximum timeout as defined
> > in the TPM Interface Specification. However, the TPM may return before
> > 5 msecs. Thus the polling interval for each iteration can be reduced,
> > which improves overall performance. This patch changes the polling sleep
> > time from 5 msecs to 1 msec.
> > 
> > Additionally, this patch renames TPM_POLL_SLEEP to TPM_TIMEOUT_POLL and
> > moves it to tpm.h as an enum value.
> > 
> > After this change, performance on a system[1] with a TPM 1.2 with an 8 byte
> > burstcount for 1000 extends improved from ~14 sec to ~10.7 sec.
> > 
> > [1] All tests are performed on an x86 based, locked down, single purpose
> > closed system. It has Infineon TPM 1.2 using LPC Bus.
> > 
> > Signed-off-by: Nayna Jain <nayna@...ux.vnet.ibm.com>
>  
> Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>

Tested-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>

/Jarkko