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Date:      Sat, 02 Feb 2019 11:26:45 +0100
From:      Andreas Longwitz <longwitz@incore.de>
To:        Konstantin Belousov <kib@freebsd.org>
Cc:        freebsd-pf@freebsd.org, Gleb Smirnoff <glebius@freebsd.org>,  Kristof Provost <kristof@sigsegv.be>
Subject:   Re: rdr pass for proto tcp sometimes creates states with expire time zero and so breaking connections
Message-ID:  <5C557065.10600@incore.de>
In-Reply-To: <20190125131409.GZ24863@kib.kiev.ua>
References:  <5BC51424.5000309@incore.de> <C4D1F141-2979-4103-957F-F0314637D978@sigsegv.be> <5BD45882.1000207@incore.de> <D5EEA773-1F0F-4FA0-A39A-486EE323907D@sigsegv.be> <5BEB3B9A.9080402@incore.de> <20181113222533.GJ9744@FreeBSD.org> <5C49ECAA.7060505@incore.de> <20190124203802.GU24863@kib.kiev.ua> <5C4A37A1.80206@incore.de> <20190125131409.GZ24863@kib.kiev.ua>

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Hello,

> Lets switch to IPI method for fetch, similar to clear.
> I do not think that the cost of fetch is too important comparing with
> the race.
> 
> diff --git a/sys/i386/include/counter.h b/sys/i386/include/counter.h
> index 7fd26d2a960..278f89123a4 100644
> --- a/sys/i386/include/counter.h
> +++ b/sys/i386/include/counter.h
> @@ -72,7 +72,12 @@ counter_64_inc_8b(uint64_t *p, int64_t inc)
>  }
>  
>  #ifdef IN_SUBR_COUNTER_C
> -static inline uint64_t
> +struct counter_u64_fetch_cx8_arg {
> +	uint64_t res;
> +	uint64_t *p;
> +};
> +
> +static uint64_t
>  counter_u64_read_one_8b(uint64_t *p)
>  {
>  	uint32_t res_lo, res_high;
> @@ -87,9 +92,22 @@ counter_u64_read_one_8b(uint64_t *p)
>  	return (res_lo + ((uint64_t)res_high << 32));
>  }
>  
> +static void
> +counter_u64_fetch_cx8_one(void *arg1)
> +{
> +	struct counter_u64_fetch_cx8_arg *arg;
> +	uint64_t val;
> +
> +	arg = arg1;
> +	val = counter_u64_read_one_8b((uint64_t *)((char *)arg->p +
> +	    UMA_PCPU_ALLOC_SIZE * PCPU_GET(cpuid)));
> +	atomic_add_64(&arg->res, val);
> +}
> +
>  static inline uint64_t
>  counter_u64_fetch_inline(uint64_t *p)
>  {
> +	struct counter_u64_fetch_cx8_arg arg;
>  	uint64_t res;
>  	int i;
>  
> @@ -108,9 +126,10 @@ counter_u64_fetch_inline(uint64_t *p)
>  		}
>  		critical_exit();
>  	} else {
> -		CPU_FOREACH(i)
> -			res += counter_u64_read_one_8b((uint64_t *)((char *)p +
> -			    UMA_PCPU_ALLOC_SIZE * i));
> +		arg.p = p;
> +		arg.res = 0;
> +		smp_rendezvous(NULL, counter_u64_fetch_cx8_one, NULL, &arg);
> +		res = arg.res;
>  	}
>  	return (res);
>  }


I have integrated this i386 counter(9) patch and using original pf.c to
some of my test servers and everything runs fine. Today I have added my
main firewall machine and will report in two weeks the result. I suppose
running counter_u64_fetch() in parallel to counter_u64_add() is not a
problem anymore.

Andreas



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