Thanks Elliott!
How do you know if there is too much RAM used for those settings?
Which metrics do you keep track of?
What would you recommend instead?
Best,
Sergio
On Mon, Oct 21, 2019, 1:41 PM Elliott Sims <elli...@backblaze.com> wrote:
> Based on my experiences, if you have a new enough kernel I'd strongly
> suggest switching the TCP scheduler algorithm to BBR. I've found the rest
> tend to be extremely sensitive to even small amounts of packet loss among
> cluster members where BBR holds up well.
>
> High ulimits for basically everything are probably a good idea, although
> "unlimited" may not be purely optimal for all cases.
> The TCP keepalive settings are probably only necessary for traffic
> buggy/misconfigured firewalls, but shouldn't really do any harm on a modern
> fast network.
>
> The TCP memory settings are pretty aggressive and probably result in
> unnecessary RAM usage.
> The net.core.rmem_default/net.core.wmem_default settings are overridden by
> the TCP-specific settings as far as I know, so they're not really
> relevant/helpful for Cassandra
> The net.ipv4.tcp_rmem/net.ipv4.tcp_wmem max settings are pretty
> aggressive. That works out to something like 1Gbps with 130ms latency per
> TCP connection, but on a local LAN with latencies <1ms it's enough buffer
> for over 100Gbps per TCP session. A much smaller value will probably make
> more sense for most setups.
>
>
> On Mon, Oct 21, 2019 at 10:21 AM Sergio <lapostadiser...@gmail.com> wrote:
>
>>
>> Hello!
>>
>> This is the kernel that I am using
>> Linux 4.16.13-1.el7.elrepo.x86_64 #1 SMP Wed May 30 14:31:51 EDT 2018
>> x86_64 x86_64 x86_64 GNU/Linux
>>
>> Best,
>>
>> Sergio
>>
>> Il giorno lun 21 ott 2019 alle ore 07:30 Reid Pinchback <
>> rpinchb...@tripadvisor.com> ha scritto:
>>
>>> I don't know which distro and version you are using, but watch out for
>>> surprises in what vm.swappiness=0 means. In older kernels it means "only
>>> use swap when desperate". I believe that newer kernels changed to have 1
>>> mean that, and 0 means to always use the oomkiller. Neither situation is
>>> strictly good or bad, what matters is what you intend the system behavior
>>> to be in comparison with whatever monitoring/alerting you have put in place.
>>>
>>> R
>>>
>>>
>>> On 10/18/19, 9:04 PM, "Sergio Bilello" <lapostadiser...@gmail.com>
>>> wrote:
>>>
>>> Message from External Sender
>>>
>>> Hello everyone!
>>>
>>>
>>>
>>> Do you have any setting that you would change or tweak from the
>>> below list?
>>>
>>>
>>>
>>> sudo cat /proc/4379/limits
>>>
>>> Limit Soft Limit Hard Limit
>>> Units
>>>
>>> Max cpu time unlimited unlimited
>>> seconds
>>>
>>> Max file size unlimited unlimited
>>> bytes
>>>
>>> Max data size unlimited unlimited
>>> bytes
>>>
>>> Max stack size unlimited unlimited
>>> bytes
>>>
>>> Max core file size unlimited unlimited
>>> bytes
>>>
>>> Max resident set unlimited unlimited
>>> bytes
>>>
>>> Max processes 32768 32768
>>> processes
>>>
>>> Max open files 1048576 1048576
>>> files
>>>
>>> Max locked memory unlimited unlimited
>>> bytes
>>>
>>> Max address space unlimited unlimited
>>> bytes
>>>
>>> Max file locks unlimited unlimited
>>> locks
>>>
>>> Max pending signals unlimited unlimited
>>> signals
>>>
>>> Max msgqueue size unlimited unlimited
>>> bytes
>>>
>>> Max nice priority 0 0
>>>
>>> Max realtime priority 0 0
>>>
>>> Max realtime timeout unlimited unlimited
>>> us
>>>
>>>
>>>
>>> These are the sysctl settings
>>>
>>> default['cassandra']['sysctl'] = {
>>>
>>> 'net.ipv4.tcp_keepalive_time' => 60,
>>>
>>> 'net.ipv4.tcp_keepalive_probes' => 3,
>>>
>>> 'net.ipv4.tcp_keepalive_intvl' => 10,
>>>
>>> 'net.core.rmem_max' => 16777216,
>>>
>>> 'net.core.wmem_max' => 16777216,
>>>
>>> 'net.core.rmem_default' => 16777216,
>>>
>>> 'net.core.wmem_default' => 16777216,
>>>
>>> 'net.core.optmem_max' => 40960,
>>>
>>> 'net.ipv4.tcp_rmem' => '4096 87380 16777216',
>>>
>>> 'net.ipv4.tcp_wmem' => '4096 65536 16777216',
>>>
>>> 'net.ipv4.ip_local_port_range' => '10000 65535',
>>>
>>> 'net.ipv4.tcp_window_scaling' => 1,
>>>
>>> 'net.core.netdev_max_backlog' => 2500,
>>>
>>> 'net.core.somaxconn' => 65000,
>>>
>>> 'vm.max_map_count' => 1048575,
>>>
>>> 'vm.swappiness' => 0
>>>
>>> }
>>>
>>>
>>>
>>> Am I missing something else?
>>>
>>>
>>>
>>> Do you have any experience to configure CENTOS 7
>>>
>>> for
>>>
>>> JAVA HUGE PAGES
>>>
>>>
>>> https://urldefense.proofpoint.com/v2/url?u=https-3A__docs.datastax.com_en_dse_5.1_dse-2Dadmin_datastax-5Fenterprise_config_configRecommendedSettings.html-23CheckJavaHugepagessettings&d=DwIBaQ&c=9Hv6XPedRSA-5PSECC38X80c1h60_XWA4z1k_R1pROA&r=OIgB3poYhzp3_A7WgD7iBCnsJaYmspOa2okNpf6uqWc&m=zke-WpkD1c6Qt1cz8mJG0ZQ37h8kezqknMSnerQhXuU&s=b6lGdbtv1SN9opBsIOFRT6IX6BroMW-8Tudk9qEh3bI&e=
>>>
>>>
>>>
>>> OPTIMIZE SSD
>>>
>>>
>>> https://urldefense.proofpoint.com/v2/url?u=https-3A__docs.datastax.com_en_dse_5.1_dse-2Dadmin_datastax-5Fenterprise_config_configRecommendedSettings.html-23OptimizeSSDs&d=DwIBaQ&c=9Hv6XPedRSA-5PSECC38X80c1h60_XWA4z1k_R1pROA&r=OIgB3poYhzp3_A7WgD7iBCnsJaYmspOa2okNpf6uqWc&m=zke-WpkD1c6Qt1cz8mJG0ZQ37h8kezqknMSnerQhXuU&s=c0S3S3V_0YHVMx2I-pyOh24MiQs1D-L73JytaSw648M&e=
>>>
>>>
>>>
>>>
>>> https://urldefense.proofpoint.com/v2/url?u=https-3A__docs.datastax.com_en_dse_5.1_dse-2Dadmin_datastax-5Fenterprise_config_configRecommendedSettings.html&d=DwIBaQ&c=9Hv6XPedRSA-5PSECC38X80c1h60_XWA4z1k_R1pROA&r=OIgB3poYhzp3_A7WgD7iBCnsJaYmspOa2okNpf6uqWc&m=zke-WpkD1c6Qt1cz8mJG0ZQ37h8kezqknMSnerQhXuU&s=PZFG6SXF6dL5LRJ-aUoidHnnLGpKPbpxdKstM8M9JMk&e=
>>>
>>>
>>>
>>> We are using AWS i3.xlarge instances
>>>
>>>
>>>
>>> Thanks,
>>>
>>>
>>>
>>> Sergio
>>>
>>>
>>>
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