From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753526AbeCFLGU (ORCPT ); Tue, 6 Mar 2018 06:06:20 -0500 Received: from mga09.intel.com ([134.134.136.24]:10755 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753024AbeCFLGS (ORCPT ); Tue, 6 Mar 2018 06:06:18 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.47,431,1515484800"; d="scan'208";a="39590256" Message-ID: <1520334372.7549.2.camel@linux.intel.com> Subject: Re: [PATCH 2/3] tpm: reduce poll sleep time between send() and recv() in tpm_transmit() From: Jarkko Sakkinen To: Mimi Zohar , Nayna Jain Cc: linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, peterhuewe@gmx.de, tpmdd@selhorst.net, jgunthorpe@obsidianresearch.com, patrickc@us.ibm.com Date: Tue, 06 Mar 2018 13:06:12 +0200 In-Reply-To: <1520276852.10396.351.camel@linux.vnet.ibm.com> References: <20180228191828.20056-1-nayna@linux.vnet.ibm.com> <20180228191828.20056-2-nayna@linux.vnet.ibm.com> <20180301092222.GC29420@linux.intel.com> <6ef601be-5627-6746-bd4a-4f391aba8b04@linux.vnet.ibm.com> <20180305105633.GE25377@linux.intel.com> <20180305180144.GE5791@linux.intel.com> <1520276852.10396.351.camel@linux.vnet.ibm.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.26.5-1build1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2018-03-05 at 14:07 -0500, Mimi Zohar wrote: > On Mon, 2018-03-05 at 20:01 +0200, Jarkko Sakkinen wrote: > > On Mon, Mar 05, 2018 at 12:56:33PM +0200, Jarkko Sakkinen wrote: > > > On Fri, Mar 02, 2018 at 12:26:35AM +0530, Nayna Jain wrote: > > > > > > > > > > > > On 03/01/2018 02:52 PM, Jarkko Sakkinen wrote: > > > > > On Wed, Feb 28, 2018 at 02:18:27PM -0500, Nayna Jain wrote: > > > > > > In tpm_transmit, after send(), the code checks for status in a loop > > > > > > > > > > Maybe cutting hairs now but please just use the actual function name > > > > > instead of send(). Just makes the commit log more useful asset. > > > > > > > > Sure, will do. > > > > > > > > > > > - tpm_msleep(TPM_TIMEOUT); > > > > > > + tpm_msleep(TPM_TIMEOUT_POLL); > > > > > > > > > > What about just calling schedule()? > > > > > > > > I'm not sure what you mean by "schedule()". Are you suggesting instead > > > > of > > > > using usleep_range(), using something with an even finer grain > > > > construct? > > > > > > > > Thanks & Regards, > > > > - Nayna > > > > > > kernel/sched/core.c > > > > The question I'm trying ask to is: is it better to sleep such a short > > time or just ask scheduler to schedule something else after each > > iteration? > > I still don't understand why scheduling some work would be an > improvement. We still need to loop, testing for the TPM command to > complete. > > According to the schedule_hrtimeout_range() function comment, > schedule_hrtimeout_range() is both power and performance friendly. > What we didn't realize is that the hrtimer *uses* the maximum range > to calculate the sleep time, but *may* return earlier based on the > minimum time. > > This patch minimizes the tpm_msleep(). The subsequent patch in this > patch set shows that 1 msec isn't fine enough granularity. I still > think calling usleep_range() is the right solution, but it needs to be > at a finer granularity than tpm_msleep() provides. > > Mimi We can move to usleep_range() in call sites where it makes sense instead of adjusting tpm_msleep() implementation... /Jarkko