From: Scott Wood <email@example.com> To: Karim Eshapa <firstname.lastname@example.org> Cc: email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.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: <email@example.com> (raw) In-Reply-To: <firstname.lastname@example.org> 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] " 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]
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