Re: [PATCH v3] ipvs: increase ip_vs_conn_tab_bits range for 64BIT

Julian Anastasov
2023-05-17T12:29:28Z

Hello,

On Tue, 16 May 2023, Abhijeet Rastogi wrote:

> Current range [8, 20] is set purely due to historical reasons
> because at the time, ~1M (2^20) was considered sufficient.
> With this change, 27 is the upper limit for 64-bit, 20 otherwise.
>
> Previous change regarding this limit is here.
>
> Link: https://lore.kernel.org/all/86eabeb9dd62aebf1e2533926fdd13fed48bab1f.1631289960.git.aclaudi@redhat.com/T/#u
>
> Signed-off-by: Abhijeet Rastogi <abhijeet.1989@gmail.com>

Looks good to me, thanks!

Acked-by: Julian Anastasov <ja@ssi.bg>

I'll post my patch on top of this.

> ---
> The conversation for this started at:
>
> https://www.spinics.net/lists/netfilter/msg60995.html
>
> The upper limit for algo is any bit size less than 32, so this
> change will allow us to set bit size > 20. Today, it is common to have
> RAM available to handle greater than 2^20 connections per-host.
>
> Distros like RHEL already allow setting limits higher than 20.
> ---
> Changes in v3:
> - Fix text width in Kconfig, now text is 70 columns, excluding tab.
> - Link to v2: https://lore.kernel.org/r/20230412-increase_ipvs_conn_tab_bits-v2-1-994c0df018e6@gmail.com
>
> Changes in v2:
> - Lower the ranges, 27 for 64bit, 20 otherwise
> - Link to v1: https://lore.kernel.org/r/20230412-increase_ipvs_conn_tab_bits-v1-1-60a4f9f4c8f2@gmail.com
> ---
> net/netfilter/ipvs/Kconfig | 27 ++++++++++++++-------------
> net/netfilter/ipvs/ip_vs_conn.c | 4 ++--
> 2 files changed, 16 insertions(+), 15 deletions(-)
>
> diff --git a/net/netfilter/ipvs/Kconfig b/net/netfilter/ipvs/Kconfig
> index 271da8447b29..2a3017b9c001 100644
> --- a/net/netfilter/ipvs/Kconfig
> +++ b/net/netfilter/ipvs/Kconfig
> @@ -44,7 +44,8 @@ config IP_VS_DEBUG
>
> config IP_VS_TAB_BITS
> int "IPVS connection table size (the Nth power of 2)"
> - range 8 20
> + range 8 20 if !64BIT
> + range 8 27 if 64BIT
> default 12
> help
> The IPVS connection hash table uses the chaining scheme to handle
> @@ -54,24 +55,24 @@ config IP_VS_TAB_BITS
>
> Note the table size must be power of 2. The table size will be the
> value of 2 to the your input number power. The number to choose is
> - from 8 to 20, the default number is 12, which means the table size
> - is 4096. Don't input the number too small, otherwise you will lose
> - performance on it. You can adapt the table size yourself, according
> - to your virtual server application. It is good to set the table size
> - not far less than the number of connections per second multiplying
> - average lasting time of connection in the table. For example, your
> - virtual server gets 200 connections per second, the connection lasts
> - for 200 seconds in average in the connection table, the table size
> - should be not far less than 200x200, it is good to set the table
> - size 32768 (2**15).
> + from 8 to 27 for 64BIT(20 otherwise), the default number is 12,
> + which means the table size is 4096. Don't input the number too
> + small, otherwise you will lose performance on it. You can adapt the
> + table size yourself, according to your virtual server application.
> + It is good to set the table size not far less than the number of
> + connections per second multiplying average lasting time of
> + connection in the table. For example, your virtual server gets 200
> + connections per second, the connection lasts for 200 seconds in
> + average in the connection table, the table size should be not far
> + less than 200x200, it is good to set the table size 32768 (2**15).
>
> Another note that each connection occupies 128 bytes effectively and
> each hash entry uses 8 bytes, so you can estimate how much memory is
> needed for your box.
>
> You can overwrite this number setting conn_tab_bits module parameter
> - or by appending ip_vs.conn_tab_bits=? to the kernel command line
> - if IP VS was compiled built-in.
> + or by appending ip_vs.conn_tab_bits=? to the kernel command line if
> + IP VS was compiled built-in.
>
> comment "IPVS transport protocol load balancing support"
>
> diff --git a/net/netfilter/ipvs/ip_vs_conn.c b/net/netfilter/ipvs/ip_vs_conn.c
> index 13534e02346c..e1b9b52909a5 100644
> --- a/net/netfilter/ipvs/ip_vs_conn.c
> +++ b/net/netfilter/ipvs/ip_vs_conn.c
> @@ -1484,8 +1484,8 @@ int __init ip_vs_conn_init(void)
> int idx;
>
> /* Compute size and mask */
> - if (ip_vs_conn_tab_bits < 8 || ip_vs_conn_tab_bits > 20) {
> - pr_info("conn_tab_bits not in [8, 20]. Using default value\n");
> + if (ip_vs_conn_tab_bits < 8 || ip_vs_conn_tab_bits > 27) {
> + pr_info("conn_tab_bits not in [8, 27]. Using default value\n");
> ip_vs_conn_tab_bits = CONFIG_IP_VS_TAB_BITS;
> }
> ip_vs_conn_tab_size = 1 << ip_vs_conn_tab_bits;
>
> ---
> base-commit: 09a9639e56c01c7a00d6c0ca63f4c7c41abe075d
> change-id: 20230412-increase_ipvs_conn_tab_bits-4322c90da216
>
> Best regards,
> --
> Abhijeet Rastogi <abhijeet.1989@gmail.com>

Regards

--
Julian Anastasov <ja@ssi.bg>