Perforce 2006.1 System Administrator's Guide
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Chapter 9
Perforce Proxy

Perforce is built to handle distributed development in a wide range of network topologies. Where bandwidth to remote sites is limited, P4P, the Perforce Proxy, improves performance by mediating between Perforce clients and servers to cache frequently transmitted file revisions. By intercepting requests for cached file revisions, P4P reduces demand on the Perforce server and network.

To improve performance obtained by multiple Perforce clients accessing a central Perforce server across a WAN, configure P4P on the side of the network close to the clients and configure the clients to access P4P; then configure P4P to access the central Perforce server. (On a LAN, you can also obtain performance improvements by setting up proxies to divert workload from the central server's CPU and disks.)

The following diagram illustrates a typical P4P configuration.

In this configuration, file revisions requested by users at a remote development site are fetched first from a central Perforce server (p4d running on central) and transferred over a relatively slow WAN. Subsequent requests for that same revision, however, are delivered from the Perforce Proxy, (p4p running on outpost), over the remote development site's LAN, reducing both network traffic across the WAN and CPU load on the central server.

System requirements

To use Perforce Proxy, you must have:

Installing P4P


To install P4P on UNIX, do the following:

  1. Download the p4p executable to the machine on which you want to run the proxy.

  2. Select a directory on this machine (P4PCACHE) in which to cache file revisions.

  3. Select a port (P4PORT) on which p4p will listen for requests from Perforce client programs.

  4. Select the target Perforce server (P4TARGET) for which this proxy will cache.


Install P4P from the Windows installer's custom/administrator installation dialog.

Running P4P

To run P4P, invoke the p4p executable, configuring it with environment variables or command-line flags. Flags you specify on the command line override environment variable settings.

For example, the following command line starts a proxy that communicates with a central Perforce server located on a host named central, listening on port 1666.

To use the proxy, Perforce client programs connect to P4P on port 1999 on the machine where the proxy runs. P4P file revisions are stored under a directory named /var/proxyroot.

Running P4P as a Windows service

To run P4P as a Windows service, either install P4P from the Windows installer, or specify the -s flag when you invoke p4p.exe, or rename the P4P executable to p4ps.exe. Set the P4POPTIONS variable to hold command-line flags to p4p.exe or p4s.exe for which there are no environment variables.

P4P flags

The following command-line flags specific to the proxy are supported.



Do not compress files transmitted from the Perforce server to P4P.

(This option reduces CPU load on the central server at the expense of slightly higher bandwidth consumption.)


Run as daemon - fork first, then run (UNIX only).


Do not fork - run as a single-threaded server (UNIX only).


Run for inetd (socket on stdin/stdout - UNIX only).


Run quietly; suppress startup messages.


Run as an NT service (Windows only).

Running p4p.exe -s is equivalent to invoking p4ps.exe.

-e size

Cache only those files that are larger than size bytes. Default is P4PFSIZE, or zero (cache all files) if P4PFSIZE is not set.

The following general options are supported.


-h or -?

Display a help message.

-L logfile

Specify the location of the log file. Default is P4LOG, or the directory from which p4p is started if P4LOG is not set.

-p port

Specify the port on which P4P will listen for requests from Perforce client programs. Default is P4PORT, or 1666 if P4PORT is not set.

-r root

Specify the directory where revisions are cached. Default is P4PCACHE, or the directory from which p4p is started if P4PCACHE is not set.

-t port

Specify the port of the target Perforce server (that is, the Perforce server for which P4P acts as a proxy). Default is P4TARGET or perforce:1666 if P4TARGET is not set.

-v level

Specifies server trace level. Debug messages are stored in the proxy server's log file. Debug messages from p4p are not passed through to p4d, and debug messages from p4d are not through to instances of p4p. Default is P4DEBUG, or none if P4DEBUG is not set.


Display the version of the Perforce Proxy.

Administering P4P

No backups required

You never need to back up the P4P cache directory.

If necessary, P4P reconstructs the cache based on Perforce server metadata.

Stopping P4P

P4P is effectively stateless; to stop P4P under UNIX, kill the p4p process with SIGTERM or SIGKILL. Under Windows, click End Process in the Task Manager.

Managing disk space consumption

P4P caches file revisions in its cache directory. These revisions accumulate until you delete them. P4P does not delete its cached files or otherwise manage its consumption of disk space.


If you do not delete cached files, you will eventually run out of disk space.

To recover disk space, remove files under the proxy's root. It is safe to delete the proxy's cached files while the proxy is running.

Determining if your Perforce client is using the proxy

If your Perforce client program is using the proxy, the proxy's version information appears in the output of p4 info.

For example, if a Perforce server is running on central:1666 and you direct your Perforce client to a Perforce Proxy running on outpost:1999, the output of p4 info resembles the following:

$ export P4PORT=outpost:1999

$ p4 info

User name: p4adm
Client name: admin-temp
Client host: remotesite22
Client root: /home/p4adm/tmp
Current directory: /home/p4adm/tmp
Client address:
Server address: central:1666
Server root: /src/p4root
Server date: 2002/10/14 15:03:05 -0700 PDT
Server version: P4D/FREEBSD4/main/36609 (2002/09/30)
Proxy version: P4P/SOLARIS26/main/36884 (2002/10/14)
Server license: P4 Admin <p4adm> 20 users (expires 2003/02/01)

P4P and protections

To apply the IP address of a Perforce Proxy user's workstation against the protections table, prepend the string proxy- to the workstation's IP address.

For instance, consider an organization with a remote development site with workstations on a subnet of The organization also has a central office where local development takes place; the central office exists on the subnet. A Perforce server resides on the subnet, and a Perforce Proxy resides on the subnet. Users at the remote site belong to the group remotedev, and occasionally visit the central office.

To ensure that members of the remotedev group use the proxy while working at the remote site, but do not use the proxy when visiting the local site, add the following lines to your protections table:

list    group    remotedev     192.168.10.*          -//...
write   group    remotedev     proxy-192.168.10.*     //...
list    group    remotedev     proxy-10*             -//...
write   group    remotedev     10.*                   //...

The first line denies list access to all users in the remotedev group if they attempt to access Perforce without using the proxy from their workstations in the 192.168.10.* subnet. The second line grants write access to all users in remotedev if they are using a Perforce Proxy server and are working from the 192.168.10.* subnet. Users of workstations at the remote site must use the proxy.

Similarly, the third and fourth lines deny list access to remotedev users when they attempt to use the proxy from workstations on the central office's subnet (, but grant write access to remotedev users who access the Perforce server directly from workstations on the central office's subnet. When visiting the local site, users from the remotedev group must access the Perforce server directly.

Determining if specific files are being delivered from the proxy

Use the -Zproxyverbose flag with p4 to display messages indicating whether file revisions are coming from the proxy (p4p) or the central server (p4d).

For instance:

$ p4 -Zproxyverbose sync noncached.txt
//depot/main/noncached.txt - refreshing /home/p4adm/tmp/noncached.txt

$ p4 -Zproxyverbose sync cached.txt
//depot/main/cached.txt - refreshing /home/p4adm/tmp/cached.txt
File /home/p4adm/tmp/cached.txt delivered from proxy server

Maximizing performance improvement

Network topologies versus P4P

If network bandwidth on the same subnet as the central Perforce server is nearly saturated, deploying proxy servers on the same subnet will not likely result in a performance improvement. Instead, deploy the proxy servers on the other side of a router so that the traffic from the clients to the proxy server is isolated to a subnet separate from the subnet containing the central Perforce server.

For example:

Deploying an additional proxy server on a subnet when network bandwidth on the subnet is nearly saturated will not likely result in a performance improvement. Instead, split the subnet into multiple subnets and deploy a proxy server in each resulting subnet.

In the illustrated configuration, a server room houses a company's Perforce server (p4d), a network storage device (NAS), and a database server (RDBMS). The server room's network segment is saturated by heavy loads placed on it by a sales force constantly querying a database for live updates, and by developers and graphic artists frequently accessing large files through the Perforce server.

Deploying two instances of Perforce Proxy (one on the developers' subnet, and one on the graphic artists' subnet) enables all three groups to benefit from improved performance due to decreased use on the server room's network segment.

Preloading the cache directory for optimal initial performance

P4P stores file revisions only when one of its clients requests them. That is, file revisions are not prefetched. Performance gains from P4P occur only after file revisions are cached.

After starting P4P, you can effectively prefetch the cache directory by creating a client workspace and syncing it to the head revision. All other clients that subsequently connect to the proxy immediately obtain the performance improvements provided by P4P.

For instance, a development site located in Asia with a P4P server targeting a Perforce server in North America can preload its cache directory by using an automated job that runs a p4 sync against the entire Perforce depot after most work at the North American site has been completed, but before its own developers arrive for work.

Distributing disk space consumption

P4P stores revisions as if there were only one depot tree. If this approach stores too much file data onto one filesystem, you can use symbolic links to spread the revisions across multiple filesystems.

For instance, if the P4P cache root is /disk1/proxy, and the Perforce server it supports has two depots named //depot and //released, you can split data across disks, storing //depot on disk1 and //released on disk2 as follows:

mkdir /disk2/proxy/released
cd /disk1/proxy
ln -s /disk2/proxy/released released

The symbolic link means that when P4P attempts to cache files in the //released depot to /disk1/proxy/released, the files are stored on /disk2/proxy/released.

Reducing server CPU usage by disabling file compression

By default, P4P compresses communication with the central Perforce server, imposing additional overhead on the server.

To disable compression, specify the -c option when you invoke p4p. This option is particularly effective if you have excess network and disk capacity and are storing large numbers of binary file revisions in the depot, because the proxy (rather than the server) decompresses the binary files from its cache before sending them to Perforce clients.

Perforce 2006.1 System Administrator's Guide
<< Previous Chapter
Perforce and Windows
Table of Contents
Perforce on the Web
Next Chapter >>
Perforce Server (p4d) Reference
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Last updated: 06/23/06