From mboxrd@z Thu Jan 1 00:00:00 1970 From: nayna@linux.vnet.ibm.com (Nayna Jain) Date: Fri, 15 Sep 2017 18:10:49 +0530 Subject: [PATCH v2 3/4] tpm: reduce tpm_msleep() time in get_burstcount() In-Reply-To: <20170913010011.myvhrj2f4i3piphl@linux.intel.com> References: <20170906125643.5070-1-nayna@linux.vnet.ibm.com> <20170906125643.5070-4-nayna@linux.vnet.ibm.com> <20170913010011.myvhrj2f4i3piphl@linux.intel.com> Message-ID: <32b07575-a895-fe45-eba3-15e47adfbcac@linux.vnet.ibm.com> To: linux-security-module@vger.kernel.org List-Id: linux-security-module.vger.kernel.org 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 >> Acked-by: Mimi Zohar >> --- >> 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 > -- To unsubscribe from this list: send the line "unsubscribe linux-security-module" in the body of a message to majordomo at vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html