add follow sysctl rule for your machine

# Required. The max_map_count should be adjusted for large RAM usage.
vm.max_map_count = 2097152
net.ipv4.tcp_max_syn_backlog = 16384
net.core.somaxconn = 16384

# These needs to be tuned for memory and RAM cache size, John
recommends that vm.dirty_ratio
# should be at least ram_cache/main_memory (+ a fudge factor). If your
box is doing a high
# amount of paging, tune these further.
vm.dirty_background_ratio = 20
vm.dirty_ratio = 70

# Probably a very good idea
net.ipv4.tcp_syncookies = 1
net.ipv4.ip_local_port_range = 32768 61000
net.core.netdev_max_backlog = 50000
net.ipv4.tcp_max_tw_buckets = 2000000

# Possibly useful for tuning for slow networks / large packets. Also
# see configurations in records.config for rec/send buffer sizes.
net.core.wmem_default = 135168
net.core.rmem_default = 135168
net.core.wmem_max = 10485760
net.core.rmem_max = 10485760

# Possibly useful
net.ipv4.neigh.default.gc_thresh3 = 8192
net.ipv4.neigh.default.gc_thresh2 = 4096
net.ipv4.neigh.default.gc_thresh1 = 1024


the links at http://people.apache.org/~zwoop/ats/sysctls.linux


2012/6/8 Saraswathi Venkataraman <[email protected]>

>  I could not find this variable in records.config proxy.config.net
> .listen_backlog****
>
> ** **
>
> *Thanks & Regards*
> *Saraswathi Venkataraman* | *Xoriant Solutions Pvt. Ltd. *
> Winchester, Hiranandani Business Park, Powai, Mumbai 400076, INDIA. ****
>
> Tel: +91 22 30511000 | Ext: 1113 | http://www.xoriant.com****
>
> ** **
>
> *From:* David Carlin [mailto:[email protected]]
> *Sent:* Thursday, June 07, 2012 1:25 AM
> *To:* [email protected]
> *Cc:* [email protected]
> *Subject:* Re: syn flooding****
>
>  ** **
>
> Bryan call recently fixed this in 3.1.4:
>
>
> https://issues.apache.org/jira/browse/TS-1211
>
> You need to increase proxy.config.net.listen_backlog in records.config
> and also the sysctl value net.ipv4.tcp_max_syn_backlog - I am using 16384.
>
> *Sent from my Verizon Wireless Phone*****
>
>
>
> -----Original message-----****
>
> *From: *Saraswathi Venkataraman <[email protected]>*
> To: *"[email protected]" <[email protected]>*
> Cc: *"[email protected]" <[email protected]>*
> Sent: *Wed, Jun 6, 2012 11:11:06 GMT+00:00*
> Subject: *syn flooding****
>
> I have configured my TS as forward transparent proxy. I generate requests
> to the TS server and measure the TPS with objects of different sizes from
> the webserver. For small objects, say 2k objects, I get TPS as 12k with
> small ram cache, and as high as 50K with large ram cache. However with
> typical and large objects(17k,1.1MB) the TPS I get for both is the same.
> And when I run with the large cache, requests for typical and large objects
> I get kernel: possible SYN flooding on port 80.
> > Sending cookies. Error in /var/log/messages
>
> Any idea how I can resolve this?
>
> Thanks & Regards
> Saraswathi Venkataraman | Xoriant Solutions Pvt. Ltd.
> Winchester, Hiranandani Business Park, Powai, Mumbai 400076, INDIA.
> Tel: +91 22 30511000 | Ext: 1113 | http://www.xoriant.com****
>

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