linux-kernel - Re: [PATCH] ipvs: Make the synchronization interval controllable

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Message-ID: <Pine.LNX.4.64.0802062329150.15729@titan.stealer.net>
Date:	Thu, 7 Feb 2008 00:12:58 +0100 (CET)
From:	Sven Wegener <sven.wegener@...aler.net>
To:	David Rientjes <rientjes@...gle.com>
cc:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ipvs: Make the synchronization interval controllable

On Wed, 6 Feb 2008, David Rientjes wrote:

> On Wed, 6 Feb 2008, Sven Wegener wrote:
>
>> diff --git a/net/ipv4/ipvs/ip_vs_sync.c b/net/ipv4/ipvs/ip_vs_sync.c
>> index 948378d..9b57ad3 100644
>> --- a/net/ipv4/ipvs/ip_vs_sync.c
>> +++ b/net/ipv4/ipvs/ip_vs_sync.c
>> @@ -143,6 +143,8 @@ char ip_vs_backup_mcast_ifn[IP_VS_IFNAME_MAXLEN];
>>  /* multicast addr */
>>  static struct sockaddr_in mcast_addr;
>>
>> +/* milliseconds between synchronization runs */
>> +int sysctl_ip_vs_sync_interval = 1000;
>>
>>  static inline void sb_queue_tail(struct ip_vs_sync_buff *sb)
>>  {
>
> How useful is a negative ip_vs_sync_interval?

Negative values will be converted to MAX_JIFFY_OFFSET by msecs_to_jiffies 
and result in a very long interval. A too long interval will be a good way 
to get your system OOM. We could use an unsigned int or even restrict the 
value with proc_dointvec_minmax. I'd prefer the latter, that's what I 
already had in my mind and it also protects from unintentionally choosing 
a too long interval.

Sven
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