From: Scott Wood <oss@buserror.net>
To: Karim Eshapa <karim.eshapa@gmail.com>
Cc: claudiu.manoil@nxp.com, roy.pledge@nxp.com,
colin.king@canonical.com, linuxppc-dev@lists.ozlabs.org,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] drivers:soc:fsl:qbman:qman.c: Sleep instead of stuck hacking jiffies.
Date: Fri, 05 May 2017 01:33:29 -0500 [thread overview]
Message-ID: <1493966009.25397.39.camel@buserror.net> (raw)
In-Reply-To: <1493964114-11296-1-git-send-email-karim.eshapa@gmail.com>
On Fri, 2017-05-05 at 08:01 +0200, Karim Eshapa wrote:
> > On 5/4/2017 5:07 PM, Scott Wood wrote:
> > > On Thu, 2017-05-04 at 06:58 +0200, Karim Eshapa wrote:
> > > > + stop = jiffies + 10000;
> > > > + /*
> > > > + * if MR was full and h/w had other FQRNI entries to produce, we
> > > > + * need to allow it time to produce those entries once the
> > > > + * existing entries are consumed. A worst-case situation
> > > > + * (fully-loaded system) means h/w sequencers may have to do 3-4
> > > > + * other things before servicing the portal's MR pump, each of
> > > > + * which (if slow) may take ~50 qman cycles (which is ~200
> > > > + * processor cycles). So rounding up and then multiplying this
> > > > + * worst-case estimate by a factor of 10, just to be
> > > > + * ultra-paranoid, goes as high as 10,000 cycles. NB, we consume
> > > > + * one entry at a time, so h/w has an opportunity to produce new
> > > > + * entries well before the ring has been fully consumed, so
> > > > + * we're being *really* paranoid here.
> > > > + */
> > >
> > > OK, upon reading this more closely it seems the intent was to delay for
> > > 10,000
> > > *processor cycles* and somehow that got turned into 10,000 jiffies
> > > (which is
> > > 40 seconds at the default Hz!). We could just replace this whole thing
> > > with
> > > msleep(1) and still be far more paranoid than was originally intended.
> > >
> > > Claudiu and Roy, any comments?
> >
> > Yes the timing here is certainly off, the code changed a few times since
> > the comment was originally written.
> > An msleep(1) seems reasonable here to me.
>
> If the previous patch with msleep(1) is OK.
> can I send a patch to slightly change the comments.
Yes.
-Scott
prev parent reply other threads:[~2017-05-05 6:33 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-29 19:46 [PATCH] drivers:soc:fsl:qbman:qman.c: Sleep instead of stuck hacking jiffies Karim Eshapa
2017-04-29 20:43 ` [PATCH] drivers:soc:fsl:qbman:qman.c: unsigned long jiffies value Karim Eshapa
2017-04-29 23:32 ` Scott Wood
2017-04-30 1:09 ` Karim Eshapa
2017-05-04 4:58 ` [PATCH v2] drivers:soc:fsl:qbman:qman.c: Sleep instead of stuck hacking jiffies Karim Eshapa
2017-05-04 21:07 ` Scott Wood
2017-05-04 23:30 ` Roy Pledge
2017-05-05 5:45 ` [PATCH v3] " Karim Eshapa
2017-06-25 2:46 ` [v3] " Scott Wood
2017-06-27 16:38 ` Leo Li
2017-05-05 6:01 ` [PATCH v2] " Karim Eshapa
2017-05-05 6:33 ` Scott Wood [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1493966009.25397.39.camel@buserror.net \
--to=oss@buserror.net \
--cc=claudiu.manoil@nxp.com \
--cc=colin.king@canonical.com \
--cc=karim.eshapa@gmail.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=roy.pledge@nxp.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).