Subject: Re: 2.6.21 -> 2.6.22 & 2.6.23-rc8 performance regression

From: Eric Dumazet <[email-masked]>
Date: Mon, 01 Oct 2007 10:35:02 +0200

Eric Dumazet a écrit :
> Denys a écrit :
>> Well, i can play a bit more on "live" servers. I have now hot-swap 
>> server with
>> full gentoo,  where i can rebuild any kernel you want, with any 
>> applied patch.
>> But it looks more like not overhead, load becoming high too "spiky", 
>> and it is
>> not just permantenly higher. Also it is not normal that all system 
>> becoming
>> unresposive (for example ping 127.0.0.1 becoming 300ms for period, 
>> when usage
>> softirq jumps to 100%).
>>
>>   
> Could you try a pristine 2.6.22.9 and some patch in 
> secure_tcp_sequence_number() like :
>
> --- drivers/char/random.c.orig 2007-10-01 10:18:42.000000000 +0200
> +++ drivers/char/random.c 2007-10-01 10:19:58.000000000 +0200
> @@ -1554,7 +1554,7 @@
> * That's funny, Linux has one built in! Use it!
> * (Networks are faster now - should this be increased?)
> */
> - seq += ktime_get_real().tv64;
> + seq += ktime_get_real().tv64 / 1000;
> #if 0
> printk("init_seq(%lx, %lx, %d, %d) = %d\n",
> saddr, daddr, sport, dport, seq);
On 32 bits machine, replace the divide by a shift  to avoid a linker 
error (undefined reference to `__divdi3'):  

seq += ktime_get_real().tv64 >> 10;