Date:	Thu, 7 Jul 2011 14:09:09 -0400
From:	Jason Baron <jbaron@...hat.com>
To:	Joe Perches <joe@...ches.com>
Cc:	gregkh@...e.de, jim.cromie@...il.com, bvanassche@....org,
	linux-kernel@...r.kernel.org, davem@...emloft.net,
	aloisio.almeida@...nbossa.org, netdev@...r.kernel.org
Subject: Re: [PATCH 08/10] dynamic_debug: make netif_dbg() call
 __netdev_printk()

On Thu, Jul 07, 2011 at 09:29:21AM -0700, Joe Perches wrote:
> On Thu, 2011-07-07 at 10:13 -0400, Jason Baron wrote:
> > On Wed, Jul 06, 2011 at 02:59:03PM -0700, Joe Perches wrote:
> > > > diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> > > > @@ -2731,10 +2731,8 @@ do {								\
> > > >  #elif defined(CONFIG_DYNAMIC_DEBUG)
> > > >  #define netif_dbg(priv, type, netdev, format, args...)		\
> > > >  do {								\
> > > > -	if (netif_msg_##type(priv))				\
> > > > -		dynamic_dev_dbg((netdev)->dev.parent,		\
> > > > -				"%s: " format,			\
> > > > -				netdev_name(netdev), ##args);	\
> > > > +	dynamic_netif_dbg(netdev, (netif_msg_##type(priv)),	\
> > > > +				  format, ##args);		\
> > > Because you've already added dynamic_netdev_dbg,
> > > maybe this should be:
> > > #define netif_dbg(priv, type, netdev, format, args...)		\
> > > do {								\
> > > 	if (netif_msg_##type(priv))				\
> > > 		dynamic_netdev_dbg(netdev, format, ##args);	\
> > > } while (0)
> > The reason I didn't add it this way is b/c I plan on converting the
> > outer 'ifs' to the jump label infrastructure - which makes the disabled
> > case just a no-op and moves the printk and tests out of line.
> 
> Perhaps you needn't do that.
> 
> I think there's little to be gained to move the test
> outwards and not perform the netif_msg##type(priv)

In this particualr case, there might not be a large gain, but when I've
converted all of the dynamic debug infrastructure to jump labels I can
consistently see througput gains of 1% on tbench testing.

> 
> > Until that is done, i could see coding it as you've suggested, but I'd
> > prefer to leave it as is (and leave future churn to within the dynamic
> > debug code as opposed to the netdevice.h header).
> 
> Shrug.  I think that dynamic_debug will have continuing
> impacts on various subsystems unless there's some generic
> __dynamic_dbg() and _prefix() mechanism introduced into
> more generic <foo>_dbg style.
> 
> Anything logging message that uses <foo>_dbg or <foo>_vdbg
> is a candidate for dynamic_debug uses, but there's no
> current generic mechanism to avoid subsystem specific needs.
> 
> Any of these could need some dynamic_debug consideration:
> 

right. looking quickly over this list there seem to be a few different
categories:

-some just alias to dev_dbg(), so they are already picked up
-some use level logging, this could be easily added to dyanmic debug -
  we store level info in the descriptor and then check it against
  a currently set level, which can be per-debug statement
-any ones that can't fit the current model could probably be easily
 converted using a callback, That is we have some dynamic debug
 function take an optional function, which if the debugging is enabled
 is called. The format string, could optionally be blank in this case,
 I guess.

So I think it could be converted while being minimaly invasive in terms
of run-time checking. In fact, that was one of my original goals was to
try and convert all the disparate debugging calls, to a more generic
infrastructure. I know some subsystem converted to use pr_debug(), to
tie into dynamic debug, but it would take a bit of work to convert the
rest...thoughts?

thanks,

-Jason


> $ grep -rPoh --include=*.[ch] "[a-z_]+_[v]?dbg\(" * | sort | uniq
> acpi_ut_allocate_object_desc_dbg(
> acpi_ut_create_internal_object_dbg(
> adc_dbg(
> add_dyn_dbg(
> airo_print_dbg(
> ata_dev_dbg(
> ata_link_dbg(
> ata_port_dbg(
> ath_dbg(
> atm_dbg(
> bat_dbg(
> bit_dbg(
> cafe_dev_dbg(
> cam_dbg(
> c_freq_dbg(
> chan_dbg(
> chan_reg_rule_print_dbg(
> cmm_dbg(
> c_pm_dbg(
> ctrl_dbg(
> __dbg(
> desc_dbg(
> dev_dbg(
> dev_vdbg(
> dma_request_channel_dbg(
> __dump_desc_dbg(
> dump_desc_dbg(
> dump_pq_desc_dbg(
> dynamic_dev_dbg(
> e_dbg(
> ehca_dbg(
> ehca_gen_dbg(
> ehci_dbg(
> ehci_vdbg(
> en_dbg(
> ep_dbg(
> ep_vdbg(
> fhci_dbg(
> fhci_vdbg(
> fit_dbg(
> gig_dbg(
> gpio_dbg(
> gru_dbg(
> hgpk_dbg(
> hid_dbg(
> hw_dbg(
> ibmvfc_dbg(
> ipath_dbg(
> ipoib_dbg(
> ipr_dbg(
> iser_dbg(
> isp_isr_dbg(
> itd_dbg(
> ite_dbg(
> l_dbg(
> lg_dbg(
> mce_dbg(
> memblock_dbg(
> mhwmp_dbg(
> mpeg_dbg(
> mpl_dbg(
> msg_dbg(
> mthca_dbg(
> netdev_dbg(
> netdev_vdbg(
> netif_dbg(
> netif_vdbg(
> nfc_dbg(
> nfc_dev_dbg(
> nsp_dbg(
> nvt_dbg(
> ohci_dbg(
> ohci_vdbg(
> oxu_dbg(
> oxu_vdbg(
> pch_dbg(
> pch_pci_dbg(
> pm_dev_dbg(
> pnp_dbg(
> pop_dbg(
> prep_dma_pq_dbg(
> prep_dma_pqzero_sum_dbg(
> prep_dma_xor_dbg(
> _print_dbg(
> print_dbg(
> pwm_dbg(
> rdev_dbg(
> reg_dbg(
> sh_keysc_map_dbg(
> slice_dbg(
> smsc_dbg(
> start_dbg(
> stop_dbg(
> sysrq_handle_dbg(
> tda_dbg(
> tgt_dbg(
> tipc_msg_dbg(
> __tuner_dbg(
> tuner_dbg(
> tveeprom_dbg(
> tx_dbg(
> uea_dbg(
> uea_vdbg(
> ugeth_dbg(
> ugeth_vdbg(
> urb_dbg(
> usb_dbg(
> vpif_dbg(
> wiphy_dbg(
> wiphy_vdbg(
> xhci_dbg(
> x_show_dbg(
> 
> 
> --
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