netdev - Re: [PATCH] bonding: add the sysfs interface to see RLB hash table

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Date:	Wed, 01 Dec 2010 14:09:21 +0900
From:	Taku Izumi <izumi.taku@...fujitsu.com>
To:	Jay Vosburgh <fubar@...ibm.com>
CC:	Eric Dumazet <eric.dumazet@...il.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	shemminger@...tta.com
Subject: Re: [PATCH] bonding: add the sysfs interface to see RLB hash table


Dear Jay Volburgh and Stephen Hemminger:

(2010/12/01 3:37), Jay Vosburgh wrote:
> Eric Dumazet<eric.dumazet@...il.com>  wrote:
> 
>> Le mardi 30 novembre 2010 à 19:01 +0900, Taku Izumi a écrit :
>>> This patch provides the sysfs interface to see RLB hash table
>>> like the following:
>>>
>>> # cat /sys/class/net/bond0/bonding/rlb_hash_table
>>>
>>> SourceIP        DestinationIP   Destination MAC   DEV
>>>   10.124.196.205  10.124.196. 81 00:19:99:XX:XX:XX eth3
>>>   10.124.196.205  10.124.196.222 00:0a:79:XX:XX:XX eth0
>>>   10.124.196.205  10.124.196. 75 00:15:17:XX:XX:XX eth4
>>>   10.124.196.205  10.124.196.  1 00:21:d8:XX:XX:XX eth3
>>>   10.124.196.205  10.124.196.205 ff:ff:ff:ff:ff:ff eth0
> 
> 	I'm reasonably sure something like this isn't going to be
> acceptable in sysfs (it's much too large).
> 
> 	In the proc file that bonding already uses, this type of
> information isn't unreasonable, but I don't think that is the best place
> for this, for two reasons.
> 
> 	First, the table may have up to 256 entries.  Therefore, a
> sufficiently populated table will easily overrun the one page of space
> available to a sysfs show function or a proc seq_printf (per iteration),
> so it will have to handle that.  The current code in bonding to do its
> proc file already iterates over the slaves; adding another iteration
> loop to handle this table seems overly complicated.  A well populated
> table would also make the current proc file's output rather verbose,
> particularly if the TLB table is added later.
> 
> 	Second, it would have to hold the hash table spin lock, which
> may provide an easy way to mess with bonding (user space doing "while 1
> cat rlb_hash_table>  /dev/null").
> 
> 	Therefore, I'd suggest this go into debugfs somewhere, perhaps a
> /sys/kernel/debug/bonding/rlb_hash_table (perhaps with a tlb_hash_table
> as the logical pairing for the TX side), readable only by root.
> 
> 	Alternatively, if there are objections to using debufs, a new
> file in /proc/net/bonding could be used, although that seems cumbersome
> (because it would have to be named to avoid conflicts, e.g.,
> /proc/net/bonding/bond0_rlb_hash_table).
> 

 I understand the sysfs is not the proper place. I have no objection to using
debugfs. I'll try to rewrite my patch.

Taku Izumi <izumi.taku@...fujitsu.com>

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