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SubjectRe: [PATCH v1 1/2] tpm: msleep() delays - replace with usleep_range() in i2c nuvoton driver
On Wed, Mar 15, 2017 at 09:51:47PM +0530, Nayna wrote:
>
>
> On 03/15/2017 09:22 PM, Jarkko Sakkinen wrote:
> > On Fri, Mar 10, 2017 at 01:45:53PM -0500, Nayna Jain wrote:
> > > Commit 500462a9de65 "timers: Switch to a non-cascading wheel" replaced
> > > the 'classic' timer wheel, which aimed for near 'exact' expiry of the
> > > timers. Their analysis was that the vast majority of timeout timers
> > > are used as safeguards, not as real timers, and are cancelled or
> > > rearmed before expiration. The only exception noted to this were
> > > networking timers with a small expiry time.
> > >
> > > Not included in the analysis was the TPM polling timer, which resulted
> > > in a longer normal delay and, every so often, a very long delay. The
> > > non-cascading wheel delay is based on CONFIG_HZ. For a description of
> > > the different rings and their delays, refer to the comments in
> > > kernel/time/timer.c.
> > >
> > > Below are the delays given for rings 0 - 2, which explains the longer
> > > "normal" delays and the very, long delays as seen on systems with
> > > CONFIG_HZ 250.
> > >
> > > * HZ 1000 steps
> > > * Level Offset Granularity Range
> > > * 0 0 1 ms 0 ms - 63 ms
> > > * 1 64 8 ms 64 ms - 511 ms
> > > * 2 128 64 ms 512 ms - 4095 ms (512ms - ~4s)
> > >
> > > * HZ 250
> > > * Level Offset Granularity Range
> > > * 0 0 4 ms 0 ms - 255 ms
> > > * 1 64 32 ms 256 ms - 2047 ms (256ms - ~2s)
> > > * 2 128 256 ms 2048 ms - 16383 ms (~2s - ~16s)
> > >
> > > Below is a comparison of extending the TPM with 1000 measurements,
> > > using msleep() vs. usleep_delay() when configured for 1000 hz vs. 250
> > > hz, before and after commit 500462a9de65.
> > >
> > > linux-4.7 | msleep() usleep_range()
> > > 1000 hz: 0m44.628s | 1m34.497s 29.243s
> > > 250 hz: 1m28.510s | 4m49.269s 32.386s
> > >
> > > linux-4.7 | min-max (msleep) min-max (usleep_range)
> > > 1000 hz: 0:017 - 2:760s | 0:015 - 3:967s 0:014 - 0:418s
> > > 250 hz: 0:028 - 1:954s | 0:040 - 4:096s 0:016 - 0:816s
> > >
> > > This patch replaces the msleep() with usleep_range() calls in the
> > > i2c nuvoton driver with a consistent max range value.
> > >
> > > Signed-of-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
> > > Cc: stable@vger.kernel.org (linux-4.8)
> > > Signed-off-by: Nayna Jain <nayna@linux.vnet.ibm.com>
> > > ---
> > > Changelog v1:
> > >
> > > - Included Jason's feedbacks related to #defines.
> >
> > What was changed?
> >
>
> Changelog v1:
> >>
> >> - Included Jason's feedbacks related to #defines.
>
> Based on Jason's review:
> - Added () in #define
> - Replaced hardcoded maximum range value with defined name.
>
> Hmm.. could have included exact details.
>
> Thanks & Regards,
> - Nayna
>
> > /Jarkko
> >

OK, I'll replace the original patch with this. Thanks.

/Jarkko

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