[DOC] document maxpipes, nosplice, option splice-{auto,request,response}
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Willy Tarreau
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@ -68,10 +68,12 @@ The following keywords are supported in the "global" section :
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* Performance tuning
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- maxconn
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- maxpipes
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- noepoll
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- nokqueue
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- nopoll
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- nosepoll
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- nosplice
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- spread-checks
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- tune.maxaccept
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- tune.maxpollevents
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@ -198,6 +200,14 @@ maxconn <number>
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connections when this limit is reached. The "ulimit-n" parameter is
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automatically adjusted according to this value. See also "ulimit-n".
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maxpipes <number>
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Sets the maximum per-process number of pipes to <number>. Currently, pipes
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are only used by kernel-based tcp splicing. Since a pipe contains two file
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descriptors, the "ulimit-n" value will be increased accordingly. The default
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value is maxconn/4, which seems to be more than enough for most heavy usages.
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The splice code dynamically allocates and releases pipes, and can fall back
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to standard copy, so setting this value too low may only impact performance.
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noepoll
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Disables the use of the "epoll" event polling system on Linux. It is
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equivalent to the command-line argument "-de". The next polling system
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@ -220,6 +230,16 @@ nosepoll
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is equivalent to the command-line argument "-ds". The next polling system
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used will generally be "epoll". See also "nosepoll", and "nopoll".
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nosplice
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Disables the use of kernel tcp splicing between sockets on Linux. It is
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equivalent to the command line argument "-dS". Data will then be copied
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using conventional and more portable recv/send calls. Kernel tcp splicing is
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limited to some very recent instances of kernel 2.6. Most verstions between
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2.6.25 and 2.6.28 are buggy and will forward corrupted data, so they must not
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be used. This option makes it easier to globally disable kernel splicing in
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case of doubt. See also "option splice-auto", "option splice-request" and
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"option splice-response".
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spread-checks <0..50, in percent>
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Sometimes it is desirable to avoid sending health checks to servers at exact
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intervals, for instance when many logical servers are located on the same
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@ -565,6 +585,9 @@ option httplog X X X X
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[no] option persist X - X X
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[no] option redispatch X - X X
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option smtpchk X - X X
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[no] option splice-auto X X X X
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[no] option splice-request X X X X
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[no] option splice-response X X X X
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[no] option srvtcpka X - X X
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option ssl-hello-chk X - X X
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option tcpka X X X X
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@ -2236,6 +2259,96 @@ option smtpchk <hello> <domain>
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See also : "option httpchk", "source"
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option splice-auto
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no option splice-auto
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Enable or disable automatic kernel acceleration on sockets in both directions
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May be used in sections : defaults | frontend | listen | backend
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yes | yes | yes | yes
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Arguments : none
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When this option is enabled either on a frontend or on a backend, haproxy
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will automatically evaluate the opportunity to use kernel tcp splicing to
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forward data between the client and the server, in either direction. Haproxy
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uses heuristics to estimate if kernel splicing might improve performance or
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not. Both directions are handled independantly. Note that the heuristics used
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are not much aggressive in order to limit excessive use of splicing. This
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option requires splicing to be enabled at compile time, and may be globally
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disabled with the global option "nosplice". Since splice uses pipes, using it
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requires that there are enough spare pipes.
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Important note: kernel-based TCP splicing is a Linux-specific feature which
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first appeared in kernel 2.6.25. It offers kernel-based acceleration to
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transfer data between sockets without copying these data to user-space, thus
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providing noticeable performance gains and CPU cycles savings. Since many
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early implementations are buggy, corrupt data and/or are inefficient, this
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feature is not enabled by default, and it should be used with extreme care.
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While it is not possible to detect the correctness of an implementation,
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2.6.29 is the first version offering a properly working implementation. In
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case of doubt, splicing may be globally disabled using the global "nosplice"
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keyword.
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Example :
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option splice-auto
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If this option has been enabled in a "defaults" section, it can be disabled
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in a specific instance by prepending the "no" keyword before it.
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See also : "option splice-request", "option splice-response", and global
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options "nosplice" and "maxpipes"
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option splice-request
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no option splice-request
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Enable or disable automatic kernel acceleration on sockets for requests
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May be used in sections : defaults | frontend | listen | backend
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yes | yes | yes | yes
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Arguments : none
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When this option is enabled either on a frontend or on a backend, haproxy
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will user kernel tcp splicing whenever possible to forward data going from
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the client to the server. It might still use the recv/send scheme if there
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are no spare pipes left. This option requires splicing to be enabled at
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compile time, and may be globally disabled with the global option "nosplice".
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Since splice uses pipes, using it requires that there are enough spare pipes.
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Important note: see "option splice-auto" for usage limitations.
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Example :
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option splice-request
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If this option has been enabled in a "defaults" section, it can be disabled
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in a specific instance by prepending the "no" keyword before it.
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See also : "option splice-auto", "option splice-response", and global options
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"nosplice" and "maxpipes"
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option splice-response
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no option splice-response
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Enable or disable automatic kernel acceleration on sockets for responses
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May be used in sections : defaults | frontend | listen | backend
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yes | yes | yes | yes
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Arguments : none
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When this option is enabled either on a frontend or on a backend, haproxy
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will user kernel tcp splicing whenever possible to forward data going from
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the server to the client. It might still use the recv/send scheme if there
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are no spare pipes left. This option requires splicing to be enabled at
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compile time, and may be globally disabled with the global option "nosplice".
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Since splice uses pipes, using it requires that there are enough spare pipes.
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Important note: see "option splice-auto" for usage limitations.
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Example :
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option splice-response
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If this option has been enabled in a "defaults" section, it can be disabled
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in a specific instance by prepending the "no" keyword before it.
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See also : "option splice-auto", "option splice-request", and global options
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"nosplice" and "maxpipes"
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option srvtcpka
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no option srvtcpka
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Enable or disable the sending of TCP keepalive packets on the server side
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