userver(1)                                                          userver(1)



[1mNAME[0m
       userver - Micro-server
       (A fairly simple web server designed for experimentation)

[1mSYNOPSIS[0m
       [1muserver[0m

       [[1m-A[22m|[1m--accepts-only[22m]      [[1m-A[22m|[1m--close-after-accept[22m]     [[1m-B[22m|[1m--block-for-[0m
       [1msend_events[22m] [[1m-C[22m|[1m--caching-on[22m] [[1m-D[22m|[1m--debug-mask [4m[22m0xN[24m] [[1m-E[22m|[1m--send-events[22m]
       [[1m-F[22m|[1m--reset-on-close[22m]  [[1m-G[22m|[1m--use-getpid[22m]  [[1m-H[22m|[1m-h[22m|[1m-?[22m|[1m--help[22m]  [[1m-I[22m|[1m--rcv-[0m
       [1msock-low-wat  [4m[22mN[24m]  [[1m-J[22m|[1m--snd-sock-low-wat  [4m[22mN[24m]   [[1m-K[22m|[1m--kdebug-mask   [4m[22m0xN[24m]
       [[1m-L[22m|[1m--full-read  [4m[22mN[24m]  [[1m-M[22m|[1m--multi-accept[22m] [[1m-N[22m|[1m--send-loop[22m] [[1m-O[22m|[1m--select-[0m
       [1mtimeout [4m[22mN[24m] [[1m-P[22m|[1m--count-sigpipes[22m] [[1m-Q[22m|[1m--ecb-hi-water [4m[22mN[24m] [[1m-R[22m|[1m--read-sock-[0m
       [1mbuf-size  [4m[22mN[24m]  [[1m-S[22m|[1m--dont-intr-select[22m]  [[1m-T[22m|[1m--port [4m[22mN[24m] [[1m-U[22m|[1m--auto-accept[22m]
       [[1m-W[22m|[1m--write-sockbuf-size  [4m[22mN[24m]  [[1m-Y[22m|[1m--send-io-events[22m]   [[1m-a[22m|[1m--async-mode[22m]
       [[1m-b[22m|[1m--ecb-buf-entries [4m[22mN[24m] [[1m-c[22m|[1m--max-conns [4m[22mN[24m] [[1m-d[22m|[1m--delay [4m[22mN[24m] [[1m-e[22m|[1m--extra-[0m
       [1maccepts [4m[22mN[24m] [[1m-f[22m|[1m--max-fds [4m[22mN[24m]  [[1m-g[22m|[1m--accept-on-close[22m]  [[1m-i[22m|[1m--interactive[22m]
       [[1m-j[22m|[1m--kernel-info[22m]     [[1m-k[22m|[1m--sigio-use-procmask[22m]    [[1m-l[22m|[1m--listenq    [4m[22mN[24m]
       [[1m-m[22m|[1m--accept-count [4m[22mN[24m] [[1m-n[22m|[1m--no-accepts[22m]  [[1m-n[22m|[1m--listen-only[22m]  [[1m-o[22m|[1m--pro-[0m
       [1mcess-fd-order            [22m[[1mup[22m|[1mdown[22m|[1mwrites-down[22m|[1mwrites-up[22m|[1mlru[22m|[1mlifo[22m|[1mfifo[22m][1m][0m
       [[1m-p[22m|[1m--procs [4m[22mN[24m] [[1m-q[22m|[1m--ecb-low-water [4m[22mN[24m]  [[1m-r[22m|[1m--eager-reads[22m]  [[1m-s[22m|[1m--conns-[0m
       [1min-server-loop[22m]   [[1m-t[22m|[1m--free-fd-threshold   [4m[22mN[24m]   [[1m-u[22m|[1m--track-max-fd  [4m[22mN[24m]
       [[1m-w[22m|[1m--eager-writes[22m] [[1m-x[22m|[1m--sigio-accepts[22m] [[1m-y[22m|[1m--memcpy[22m] [[1m-z[22m|[1m--rejection-[0m
       [1mrate[22m]  [[1m--close-after-sock-init[22m]  [[1m--close-after-read[22m]  [[1m--close-after-[0m
       [1mparse[22m] [[1m--send-polls-for-accepts[22m] [[1m--cache-table-size [4m[22mN[24m]  [[1m--cache-max-[0m
       [1mbytes   [4m[22mN[24m]   [[1m--cache-max-file-size   [4m[22mN[24m]   [[1m--cache-max-load-factor  [4m[22mN[24m]
       [[1m--cache-table-print[22m] [[1m--cache-lock-pages[22m]  [[1m--cache-for-spec[22m]  [[1m--use-[0m
       [1msendfile[22m]    [[1m--use-accept-send[22m]    [[1m--use-madvise[22m]   [[1m--trace-summary[22m]
       [[1m--trace-summary-only[22m] [[1m--use-poll[22m] [[1m--use-epoll[22m]


[1mDESCRIPTION[0m
       [1muserver [22mis a micro web server that is meant to be  used  to  experiment
       with  the  design and implementation of web servers.  In particular the
       original intention was to permit experimental comparisons of  different
       event  dispatch mechanisms within the same appliication framework.  For
       this reason there are lots and lots and lots of parameters.   They  are
       mainly used to control the behaviour of the server.

       Some  of  the design philosophy and experimental results obtained using
       this server are described in [Brecht-2001].  One of note  is  that  all
       data  structures  are  allocated  at initialization and are not resized
       (grown).  This helps to ensure that experiments can be repeated because
       with  dynamic sizing of data structures different loads could result in
       different server behaviour.

       [1mIMPORTANT: [22mThis micro web server is not meant to be  a  full-blown  web
       server.  It is specifically designed for conducting performance experi-
       ments.  For that reason design decisions were made in favour of produc-
       ing repeatable experiments.


[1mEXAMPLES[0m
       userver
              This starts the [1muserver [22mwith it's all of its default options.


       userver --max-conns 300 --accept-count 25
              This  command  causes  the [1muserver [22mserver to limit the number of
              simultaneous connections to 300.  When an event indicating  that
              a  new  connection  is  requested  accept is called continuously
              until either 25 new connections are accepted, or  there  are  no
              more outstanding connections.


       userver --max-conns 300 --accept-count 0
              This  command  causes  the [1muserver [22mserver to limit the number of
              simultaneous connections to 300.  When an event indicating  that
              a  new connection is requested accept is called repeatedly until
              there are no more outstanding connections.  (Note that --accept-
              count=0  means  an infinite number of connections, i.e., no lim-
              its).


       userver --port 6800 --max-conns 300 --listenq 128
              This command causes [1muserver [22mto listen  for  incoming  connection
              requests on port 6800.  It uses a listen queue of length 128 and
              it will permit up to 300 simultaneous connections.   Once  there
              are  300  open  connections  it  will not accept new connections
              until an existing connection is closed.


       userver --port 6800 --max-conns 300 --listenq 128 --use-poll
              This is the same as above except using  [4mselect()[24m  calls  to  get
              events the [1muserver [22mwill use [4mpoll().[0m


       userver --port 6800 --max-conns 300 --listenq 128 --use-epoll
              This  is  the  same  as  above  except using [4mpoll()[24m calls to get
              events the [1muserver [22mwill use [4mepoll().[0m


       userver   -C    --cache-table-size=10000    --cache-max-bytes=262144000
       --cache-max-file-size=1048576
              Caching is turned on.  Caching parameters limit  the  number  of
              files that are cached to 10000, the total number of bytes cached
              to 250 MB, and the size of the largest file that can  be  cached
              to 1 MB.


[1mOPTIONS[0m

       The operation of [1muserver [22mcan be controlled through a number of options.
       The tool supports  both  short  (one-character)  and  long  (arbitrary-
       length) option names.  Short options are prefixed with a single leading
       dash (-), long options with a double-dash (--).  Multiple short options
       can  be grouped together (e.g., ``[1m-rw[22m'' is equivalent to ``[1m-r -w[22m'') and
       long options can be abbreviated so long as they remain unique.  Parame-
       ters  to  options  can be specified either by following the long option
       name with an equal sign and the parameter value (e.g., [1m--port=6800[22m)  or
       by  separating  the option name and value with whitespace (e.g., [1m--port[0m
       [1m6800[22m).


[1mOPTIONS (GENERAL)[0m


       [1m-c N[0m

       [1m--max-conns=[4m[22mN[0m
              The maximum number of simultaneous connections the  server  will
              handle.   Note  that  this is typically limited by the number of
              open file descriptors permitted.  Once  the  maximum  number  of
              open  connections  is  reached  incoming connection requests are
              refused until an existing connection is close.  Note  that  idle
              connections  can  be  timed out eventually (but this hasn't been
              tested lately).  This is also used to size a number of  internal
              data structures that are allocated at initialization time.


       [1m-f N[0m

       [1m--max-fds=[4m[22mN[0m
              The  maximum number of open file descriptors permitted.  I can't
              recall if this is actually enforced  but  it  is  used  to  size
              internal  data  structures.   Note  that there is a relationship
              between [1m--max-conns [22mand  [1m--max-fds.   [22mIf  files  are  not  being
              cached  you could (in the extreme case) have one fd used for the
              socket connection and one fd used for the  open  file.   So  one
              needs  to  set  [1m--max-fds [22m= more than 2 x [1m--max-conns.  [22mNote: it
              should be greater because of some descriptors that are  used  up
              by stdin, out, err, and a few open files, etc.


       [1m-m N[0m

       [1m--accept-count=[4m[22mN[0m
              Call  accept  repeatedly  until  either, [1m--max-conns [22mis reached,
              [1maccept() [22mreturns EWOULDBLOCK, or [4mN[24m  new  connections  have  been
              accepted.   Note that the value of [4mN[24m can make a substantial dif-
              ference in the performance of event  dispatch  mechanisms  under
              heavy loads.  See [Brecht-2001].


       [1m-T N[0m

       [1m--port=[4m[22mN[0m
              Specify  the  port number that the server should listen for con-
              nections on.


       [1m-l N[0m

       [1m--listenq=[4m[22mN[0m
              Specify the length of the appliation's listen queue.  This spec-
              ifies  how  many connection requests are allowed to be queued in
              the application before the kernel  rejects  incoming  connection
              requests.


       [1m-L[22m[1 | 2]

       [1m--full-read=[22m[1 | 2]
              Affects  how calling read works.  If this is set to 1 the server
              will loop on reading the socket  until  the  read  fails.   This
              mainly  happens  either  because  there  is nothing left to read
              because the other end has been closed or  until  it  would  have
              blocked (EWOULDBLOCK).

              If  a  value  of  1 is used the loop on reads will only occur on
              calls to read that occur as a result of an event indicating that
              the first read should be done.  If a value of 2 is used the loop
              on reads occur as above but if [1m--eager-reads  [22mis  also  set  the
              server  will  loop on eager reads (i.e., those that will be done
              immediately following a the acceptance and setup  of  a  connec-
              tion).


       [1m-H[0m

       [1m-h[0m

       [1m-?[0m

       [1m--help [22mPrint out the usage message.


       [1m-M N[0m

       [1m--multi-accept=[4m[22mN[0m
              Use  the  [4mmultiaccept()[24m  system  call to perform accepts.  NOTE:
              this was a system call that we added to and experimented with in
              Linux.   The  idea  here is that since we are repeatedly calling
              [4maccept()[24m to accept a bunch of connections,  why  not  provide  a
              system  call  that allows up to a maximum of [4mN[24m connections to be
              accepted in one system call.


       [1m-S[0m

       [1m--dont-intr-select[0m
              Disable asynchrnous event notification when calling [4mselect().[24m  I
              believe  that this was initially meant to work for SIGIO and for
              SEND.


       [1m-d N[0m

       [1m--delay=[4m[22mN[0m
              The idea was to introduce a delay that might simulate work being
              done  by  the  server  (like  some  computation and/or a dynamic
              request).  I couldn't find a good  method  for  delaying  for  a
              specified  amount  of time (note that it should be small) with a
              enough accuracy.


       [1m-e N[0m

       [1m--extra-accepts=[4m[22mN[0m
              While in the middle of processing events that have been obtained
              (e.g.,  from  select, or some other mechansim) periodically poll
              for new connection requests.  In this case every time [4mN[24m descrip-
              tors  are  processed we check for new connection requests.  Note
              that this open was never used effectively.  I found it easier to
              use and tune the [1m--accept-count [22moption.


       [1m-g[0m

       [1m--accept-on-close[0m
              When  a  connection is closed check to see if there are any out-
              standing connection requests.  Note: that this  only  occurs  if
              the  maximum  number of connections was reached and now a closed
              connection will reduce the number of  connections  below  [1m--max-[0m
              [1mconns.[0m


       [1m-o [up|down|writes-down|writes-up|lru|lifo|fifo][0m

       [1m--process-fd-order[0m
              [up|down|writes-down|writes-up|lru|lifo|fifo]

              Change  the  order  in which file descriptors are handled.  They
              are numbered from 0 to [4mN[24m so the uptions are:

              up:    from 0 to N

              down:  from N to 0

              writes-down:
                     to writes from N to 0, then reads from N to 0

              writes-up:
                     to writes from 0 to N, then reads from 0 to N

              lru:   least recently descriptor touched first

              lifo:  first descriptor (connection) added to the set first

              filo:  first descriptor (connection) added to the set last


       [1m-p N[0m

       [1m--procs=[4m[22mN[0m
              Start [4mN[24m copies of the server.  Note that this option hasn't been
              tested in a long time and is almost certain to cause problems.


       [1m-s[0m

       [1m--conns-in-server-loop[0m
              Add an additional poll for new connections each time through the
              server loop.


       [1m-t N[0m

       [1m--free-fd-threshold=[4m[22mN[0m
              When the maximum number of connections  [1m--max-conns  [22mis  reached
              the  server  stops  checking  for  incoming  connections.   This
              options controls when the  server  starts  checking  again.   It
              starts  checking  again  after  [4mN[24m connections can be accomodated
              before reaching [1m--max-conns.[0m


       [1m-u[0m

       [1m--track-max-fd[0m
              The server currently keeps track of the maximum fd ever used and
              uses  that  as  a  parameter  to calls like select.  This option
              implements code to dynamically keep track of  the  maximum  file
              descriptor  currently  used.   Note  that this requires a bit of
              extra processing but it's probably not noticable, especially  if
              it can save estra overhead on copying fdsets and processing time
              in event mechanisms (e.g., select).


       [1m-r[0m

       [1m--eager-reads[0m
              try to eagerly read from new connections.  Call [1mread() to try to[0m
              [1mread  the request as soon as [22mthe new connection is accepted.  In
              this mode the server optimistically assumes that  data  will  be
              available  for reading when a connection is made on a new socket
              (or very shortly after).  If the assumption  is  incorrect,  the
              read  call simply returns with the error EWOULDBLOCK.  Later the
              event notification mechanism will indicate when  the  socket  is
              readable.


       [1m-w[0m

       [1m--eager-writes[0m
              try  to  eagerly  perform  writes  to  new  connections when the
              response is available.  Both [1m--eager-read [22mand [1m--eager-write [22malso
              try to take advantage of any potential locality effects by work-
              ing on the most recently used file descriptor and socket.


       [1m-y[0m

       [1m--memcpy[0m
              Use the [1mmemcpy [22mlibrary call to copy interest sets before calling
              select.   This  is done rather than doing a straight assignment.
              This exists because the size of the interest set could be  large
              and  I don't know how clever a compiler would be about assigning
              large data structures.  NOTE: it currently copies the side of an
              fd_set.   This should be changed to only copy the amount of data
              required for the maximum fd of interest.


       [1m-z[0m

       [1m--rejection-rate[0m
              Use the [1mrejection-rate [22mis not yet implemented.  The ideas  would
              be  to  specify the frequency with which new connection requests
              should be rejected.


       [1m--use-sendfile[0m
              Use the [1msendfile() [22mcall on systems that have it available.  This
              is only used for uncached files.


       [1m--use-madvise[0m
              Use  madvise() calls to provide the kernel with hints that files
              are being read sequentially and when they should  no  longer  be
              cached.


       [1m--use-poll[0m
              Use poll() to get events instead of select.


       [1m--use-epoll[0m
              Use epoll() to get events instead of select.


[1mOPTIONS FOR CONTROLLING SOCKETS[0m


       [1m-F[0m

       [1m--reset-on-close[0m
              Calls [4mshutdown()[24m instead of [4mclose().[0m
              WARNING do not use this for a real system!!!


       [1m-I N[0m

       [1m--rcv-sock-low-wat=[4m[22mN[0m
              Sets  the  sockets  receive  buffer's  low water mark to [4mN.[24m  Not
              available on all systems.


       [1m-J[22mN

       [1m--snd-sock-low-wat=[22mN
              Sets the sockets send buffer's low water mark to [4mN.[24m  Not  avail-
              able on all systems.


       [1m-O N[0m

       [1m--select-timeout=[4m[22mN[0m
              Set the timeout option to the [4mselect()[24m system call.


       [1m-R N[0m

       [1m--read-sockbuf-size=[4m[22mN[0m

       [1m-W N[0m

       [1m--write-sockbuf-size=[4m[22mN[0m
              Set  the  size  of  the read or write socket buffers.  Note that
              increasing these may help significantly for large transfers.


       [1m--use_tcp_cork[0m
              Cork the TCP queue when writing the header for the reply.   Cur-
              rently only implemented for the sendfile portion of the code.


[1mOPTIONS FOR USE WITH SIGIO[0m


       [1m-a[0m

       [1m--sigio-accepts[0m
              Use  asynchronous  notification  via SIGIO to accept new connec-
              tions.  Asynchronous notification may sound costly at first  but
              consider  that  some form of asynchronous notificaion may be the
              only way for an application that is in the middle  of  something
              (e.g., computation) to find out about a connection requests.


       [1m-k[0m

       [1m--sigio-use-procmask[0m
              To disable and later enble asynchronous notification of incoming
              requests when using SIGIO one can use [1mfcntl() [22mto turn off and on
              asynchronous  notification  or use [1msigprocmask().  [22mBe careful of
              race conditions.  By default the server uses  [1mfcntl()  [22mbut  this
              option says to use [1msigprocmask() [22minstead.

[1mOPTIONS FOR CACHING[0m


       [1m-C[0m

       [1m--caching-on[0m
              Turns caching on.


       [1m--cache-table-size=[4m[22mN[0m
              Specifies  the size of the hash table used to cached files.  One
              entry is used per cached file.  NOTE: if  the  [1m--cache-max-load-[0m
              [1mfactor [22mis exceeded the server will print a message and exit.  We
              do not automatically increase the size of the hash table because
              we  want  to  ensure identical and repeatable behaviour from one
              experiment to the next.


       [1m--cache-max-load-factor=[4m[22mN[0m
              Specifies the maximum number of entries that can  be  filled  in
              the  hash  table,  expressed  as a percentage of the table size.
              For example [1m--cache-max-load-factor = 70  [22mwill  not  permit  the
              hash  table to become greater than 70% full.  If it does, a mes-
              sage is printed and the server exits.


       [1m--cache-max-bytes=[4m[22mN[0m
              Specifies the maximum number of bytes cached.


       [1m--cache-max-file-size=[4m[22mN[0m
              Don't cache files larger than [4mN[24m bytes.


       [1m--cache-table-print[0m
              When the program ends, print out the contents of the hash  table
              used for caching.


       [1m--cache-for-spec[0m
              This  enables  a special hash function that does perfect hashing
              on URLs requested by SpecWeb99.  This is intended for experimen-
              tation only.


       [1m--cache-lock-pages[0m
              Lock  all cached pages into memory (must run as root for this to
              work).


[1mOPTIONS FOR DEBUGGING[0m


       [1m-D 0xN[0m

       [1m--debug-mask=[4m[22m0xN[24m[1m][0m
              Specify a debug mask.  For maximum debugging detail use [1m--debug-[0m
              [1mmask  = [4m[22m0xffffffff.[24m  To turn debugging messages off use [1m--debug-[0m
              [1mmask = [4m[22m0x0.[24m  See debug.h for details.   Note:  that  to  compile
              without debugging also see debug.h.


       [1m--trace-summary[0m
              Keep  track  of  information  regarding system calls and print a
              summary.  If tracing is enabled  a  list  of  each  event  being
              traced will be dumped to a trace output file.


       [1m--trace-summary-only[0m
              Keep  track  of  information  regarding system calls and print a
              summary.  If this option is enabled individual  events  are  not
              actually  recorded  but instead information to produce a summary
              of each event type is tracked. For example, minimum, maximum and
              average call times for each system call being traced.


       [1m-i[0m

       [1m--interactive[0m
              Turns  on  interactive  mode.  The server stops between calls to
              process events and prompts the user for input.  This permits the
              user to query some of the state of the server or to step through
              server execution.  At the prompt type 'h' or '?' for a  list  of
              commands.


       [1m-P[0m

       [1m--count-sigpipes[0m
              Install  a  signal handler that simply counts the number of SIG-
              PIPE signals received.

[1mOPTIONS FOR EXPERIMENTS RELATED TO BOUNDING PERFORMANCE[0m

       These options are designed to have the server stop processing a request
       at various stages of a requests life.  It stops handling the request by
       closing it's end of the socket and not working on that request anymore.
       I've  attempted to list these in the order of earliest time to drop the
       request to latest.  The idea is that by running a series of experiments
       by  using each of these options one might be able to get a sense of how
       much additional stage costs.


       [1m-n[0m

       [1m--no-accepts[0m

       [1m--listen-only[0m
              This puts the server into a mode where it only ever  listens  to
              requests.   It  never makes any attempt to process requests.  So
              it never even accepts any requests.  The believe  is  that  this
              might  be  used  to provide insights into the amount of overhead
              incurred when kernel  TCP  SYN  queues  and  application  listen
              queues become full.


       [1m-A[0m

       [1m--accepts-only[0m

       [1m--close-after-accept[0m
              In  this  mode the server accepts and closes incoming connection
              requests as quickly as possible.  At  the  time  this  was  done
              [4mclose()[24m  would  block  until  the call completed (despite the fd
              being in non  blocking  mode).   So  immediately  after  calling
              [4maccept()[24m the connection terminated by calling [4mclose().[0m


       [1m--close-after-sock-init[0m
              The server accepts a connection, initializes the socket (setting
              socket options like socket buffer sizes, non blocking mode, etc)
              and then it closes the connection.


       [1m--close-after-read[0m
              The  server  accepts  a connection, initializes the socket reads
              the request and then closes the connection.


       [1m--close-after-parse[0m
              The server accepts a connection, initializes  the  socket  reads
              the request, parses the requests and then closes the connection.

[1mOPTIONS FOR USE WITH THE SEND ENHANCED KERNEL[0m

       WARNING: these options are highly experimental and subject to  continu-
       ous change.

       These options specify how the [1muserver [22minteracts with new Linux Scalable
       Event  Notification  and  Delivery  (SEND)  kernel   mechanisms.    See
       [Ostrowski-2000] for more details on SEND.


       [1m-K 0xN[0m

       [1m--kdebug-mask=[4m[22m0xN[24m[1m][0m
              Specify  a  debugging  mask which is passed to the [4mevtctl[24m system
              call to set a kernel debugging mask for the SEND  related  parts
              of the kernel.


       [1m--send-polls-for-accepts[0m
              The send loop polls for new connections.


       [1m-B[0m

       [1m--block-for-send_events[0m
              When  there  are  not more events to process, block and wait for
              one or more new events by calling [4mevtctl().[0m


       [1m-E[0m

       [1m--send-events[0m
              Use send events. This version does not do notification.


       [1m-G[0m

       [1m--use_getpid[0m
              If we aren't blocking to wait for events (by calling evtctl)  we
              may  wish  to  make a system call to give the kernel a chance to
              deliver events to the application (since they are delivered when
              returning  from a syscall.  In this case we use getpid() because
              it is likely fast.


       [1m-Y[0m

       [1m--send-io-events[0m
              Use send events. This version does do notification.


       [1m-N[0m

       [1m--send-loop[0m
              Use the send loop.  Can potentially get and process send  events
              even  while  using  select.  This bypasses the use of the select
              call.


       [1m-b N[0m

       [1m--ecb-buf-entries=[4m[22mN[0m
              How many events can be stored in the application's event control
              buffer (ecb).


       [1m-Q N[0m

       [1m--ecb-hi-water=[4m[22mN[0m
              Set the high water mark used for the event control buffer (ecb).
              One of the things we've tried is to turn event delivery off when
              the  [4m--ecb-hi-water[24m  mark  is  reached and then to turn delivery
              back on when the [4m--ecb-low-water[24m mark is reached.


       [1m-q N[0m

       [1m--ecb-low-water=[4m[22mN[0m
              Set the low water mark used for the event control buffer  (ecb).
              One of the things we've tried is to turn event delivery off when
              the [4m--ecb-hi-water[24m mark is reached and  then  to  turn  delivery
              back on when the [4m--ecb-low-water[24m mark is reached.


       [1m-U[0m

       [1m--auto-accept[0m
              Turn on the SEND kernel's auto accept mechanisms.  When new con-
              nection requests arrive the kernel  automatically  accepts  them
              (auto  accepts  'em)  and notifies the application with an event
              containing the new connection's fd.


       [1m--use-accept-send[0m
              Use a special version of accept that returns  event  information
              related to the accepted connection/socket.


       [1m-j[0m

       [1m--kernel-info[0m
              Experimental: was to tell the application that the kernel has an
              interface available for obtaining  more  information  about  the
              size  and  number of entries in some of the kernel queues (e.g.,
              the TCP SYNQs and the application's listenq).

[1mOUTPUT[0m
       This section describes portions of the output produced during the  exe-
       cution of the [1muserver.[0m


       The first portion of output lists the program name and the command line
       parameters.  The second portion of output  lists  the  setting  of  all
       options.   This  is  the most reliable way to find out the default set-
       tings for some options.


       The next two sections identify operating system and per user or process
       limits.

       The  remainder  of  the  output provides more information about default
       settings of various parameters and a large number of  statistics  about
       the execution of the server.


[1mAUTHORS[0m
       [1muserver  [22mwas  developed  by  Tim Brecht by starting with some micro web
       servers originally developed by Abhishek Chandra  and  David  Mosberger
       [Chandra-2001].   David  Pariag contributed the current caching engine.
       One of the hash functions is from Bob Jenkin's web site.


[1mBUGS[0m
       Probably many.

       NOTE: very few if any checks are performed to see if the combination of
       options  being used makes sense.  For example, the behaviour from using
       both the [1m--select-loop [22mand [1m--send-loop [22moptions is undefined.

       Always be sure to double-check results and don't fall prey to measuring
       client-performance  instead of server performance!  The tool [1mhttperf [22mis
       very good at generating loads.

       Many of the single letter options are difficult to relate  to  anything
       meaningful.  As  the number of options grew I eventually started to run
       out of alphabet and added long options.

       The user-interface definitely could be improved.  A  simple  configura-
       tion file might be more suitable than the many command-line options.


[1mREFERENCES[0m
       [Brecht-2001]    Tim Brecht and Michal Ostrowski, Exploring the Perfor-
                        mance of Select-based Internet Servers, HP Labs  Tech-
                        nical Report HPL-2001-314, November, 2001.


       [Chandra-2001]   A.  Chandra  and  D.  Mosberger,  Scalability of Linux
                        Event-Dispatch Mechanisms,  Proceedings  of  the  2001
                        USENIX Annual Technical Conference, June 2001.


       [Ostrowski-2000] Michal Ostrowski, A Mechanism for Scalable Event Noti-
                        fication and Delivery in Linux, M.Math Thesis, Depart-
                        ment  of  Computer  Science,  University  of Waterloo,
                        November, 2000.



                                  1 Aug 2003                        userver(1)
