linux-kernel - Re: [PATCH] CIFS: Decrease reconnection delay when switching nics

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Message-ID: <512DE8A6.9030000@samba.org>
Date:	Wed, 27 Feb 2013 12:06:14 +0100
From:	"Stefan (metze) Metzmacher" <metze@...ba.org>
To:	Dave Chiluk <chiluk@...onical.com>
CC:	Steve French <sfrench@...ba.org>, linux-cifs@...r.kernel.org,
	samba-technical@...ts.samba.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] CIFS: Decrease reconnection delay when switching nics

Hi Dave,

> When messages are currently in queue awaiting a response, decrease amount of
> time before attempting cifs_reconnect to SMB_MAX_RTT = 10 seconds. The current
> wait time before attempting to reconnect is currently 2*SMB_ECHO_INTERVAL(120
> seconds) since the last response was recieved.  This does not take into account
> the fact that messages waiting for a response should be serviced within a
> reasonable round trip time.

Wouldn't that mean that the client will disconnect a good connection,
if the server doesn't response within 10 seconds?
Reads and Writes can take longer than 10 seconds...

> This fixes the issue where user moves from wired to wireless or vice versa
> causing the mount to hang for 120 seconds, when it could reconnect considerably
> faster.  After this fix it will take SMB_MAX_RTT (10 seconds) from the last
> time the user attempted to access the volume or SMB_MAX_RTT after the last
> echo.  The worst case of the latter scenario being
> 2*SMB_ECHO_INTERVAL+SMB_MAX_RTT+small scheduling delay (about 130 seconds).
> Statistically speaking it would normally reconnect sooner.  However in the best
> case where the user changes nics, and immediately tries to access the cifs
> share it will take SMB_MAX_RTT=10 seconds.

I think it would be better to detect the broken connection
by using an AF_NETLINK socket listening for RTM_DELADDR
messages?

metze


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