Date: Thu, 6 Dec 2001 15:42:16 -0700 From: Chad David <davidc@acns.ab.ca> To: Luigi Rizzo <rizzo@aciri.org> Cc: Robert Watson <rwatson@FreeBSD.org>, cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org Subject: Re: cvs commit: src/share/man/man7 tuning.7 Message-ID: <20011206154216.A94670@colnta.acns.ab.ca> In-Reply-To: <20011206121009.B74685@iguana.aciri.org>; from rizzo@aciri.org on Thu, Dec 06, 2001 at 12:10:09PM -0800 References: <200112061950.fB6JoZS71169@freefall.freebsd.org> <20011206121009.B74685@iguana.aciri.org>
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--C7zPtVaVf+AK4Oqc Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Thu, Dec 06, 2001 at 12:10:09PM -0800, Luigi Rizzo wrote: > On Thu, Dec 06, 2001 at 11:50:35AM -0800, Robert Watson wrote: > > rwatson 2001/12/06 11:50:35 PST > > > > Modified files: > > share/man/man7 tuning.7 > > Log: > > o Add an additional .Pp between the send/recvbuffer comments and > > the ones on ipfw. Note to self: why does ipfw/dummynet count as > > a sysctl in tuning(7)? > > I have to admit it is the first time i read this manpage, and from > the CGI interface on www.freebsd.org, so the one i see might > be out of date, but I have the impression that the document should > be slightly restructured, by putting a short introduction paragraph > listing which subsystems are covered, mentioning that most of the > subsystems can be controlled/configured using kernel config options, > sysctls and boot-time tunables, and then completely removing the > SYSCTL section (whose content goes into the subsystem's sections). How is something like this? It isn't quite as broken out as it could be, mostly because I tried to use as much of the original text as possible. I have fixed a few spelling mistakes etc. but it still needs work. I did add a litte text around the keepalive section. The question I struggled with while putting this together was do we group by system (disk, memory, network etc.), or do we group by tunable section (filesystem layout etc., sysctl's and tunables, kernel config, etc.)? Now that I've gone through it all, I think it should be structured more like was suggested then how I updated it. By trying to group it by tunable section I ended up with some data spread all over the file. Another question was if we wanted to maintain Matt's informal tone? Some terms like "network suds" give the manual a more playful feeling which I tried not to kill (although I did change a lot of 'I's to 'we's). -- Chad David davidc@acns.ab.ca ACNS Inc. Calgary, Alberta Canada --C7zPtVaVf+AK4Oqc Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="tuning2.7" .\" Copyright (c) 2001, Matthew Dillon. Terms and conditions are those of .\" the BSD Copyright as specified in the file "/usr/src/COPYRIGHT" in .\" the source tree. .\" .\" $FreeBSD: src/share/man/man7/tuning.7,v 1.27 2001/12/06 20:27:44 rwatson Exp $ .\" .Dd May 25, 2001 .Dt TUNING 7 .Os .Sh NAME .Nm tuning .Nd performance tuning under FreeBSD .Sh SYNOPSIS This manual page describes various practices and tunable variables that can affect the performance of FreeBSD under various loads in different environments. The layout of this manaul is designed to simplify the search for tuning information about specific sections of a system, but should really be read in its entirety, as it contains a lot of useful information that is not generally available in other documents. .Sh STORAGE This sections discusses issues related to the storage subsystems in FreeBSD. Storage subsystems include both disk and filesystem, and memory and swap. .Ss DISKS Need a little more here! .Pp There are a number of compile time options that can be configured to affect installed disks. The .Xr config 8 manual page and the handbook are good starting points for learning how to do this. .Pp .Dv SCSI_DELAY and .Dv IDE_DELAY may be used to reduce system boot times. The defaults are fairly high and can be responsible for 15+ seconds of delay in the boot process. Reducing .Dv SCSI_DELAY to 5 seconds usually works (especially with modern drives). Reducing .Dv IDE_DELAY also works but you have to be a little more careful. .Ss FILESYSTEMS When using .Xr disklabel 8 to lay out your filesystems on a hard disk it is important to remember that hard drives can transfer data much more quickly from outer tracks than they can from inner tracks. To take advantage of this you should try to pack your smaller filesystems and swap closer to the outer tracks, follow with the larger filesystems, and end with the largest filesystems. It is also important to size system standard filesystems such that you will not be forced to resize them later as you scale the machine up. A common layout, in order, is a 128M root, 1G swap, 128M .Pa /var , 128M .Pa /var/tmp , 3G .Pa /usr , and use any remaining space for .Pa /home . .Pp How you size your .Pa /var partition depends heavily on what you intend to use the machine for. This partition is primarily used to hold mailboxes, the print spool, and log files. Some people even make .Pa /var/log its own partition (but except for extreme cases it isn't worth the waste of a partition ID). If your machine is intended to act as a mail or print server, or you are running a heavily visited web server, you should consider creating a much larger partition \(en perhaps a gig or more. It is very easy to underestimate log file storage requirements. .Pp Sizing .Pa /var/tmp depends on the kind of temporary file usage you think you will need. 128M is the minimum we recommend. Also note that sysinstall will create a .Pa /tmp directory, but it is usually a good idea to make .Pa /tmp a softlink to .Pa /var/tmp after the fact. Dedicating a partition for temporary file storage is important for two reasons; first, it reduces the possibility of filesystem corruption in a crash, and second it reduces the chance that a runaway process that fills up .Oo Pa /var Oc Ns Pa /tmp will blow up more critical subsystems (mail, logging, etc). Filling up .Oo Pa /var Oc Ns Pa /tmp is a very common problem to have. .Pp In the old days there were differences between .Pa /tmp and .Pa /var/tmp , but the introduction of .Pa /var (and .Pa /var/tmp ) led to massive confusion by program writers, so today programs haphazardly use one or the other and thus no real distinction can be made between the two; therefore, it makes sense to have just one temporary directory. However you handle .Pa /tmp , the one thing you do not want to do is leave it sitting on the root partition where it might cause root to fill up or possibly corrupt root in a crash/reboot situation. .Pp The .Pa /usr partition holds the bulk of the files required to support the system and a subdirectory within it called .Pa /usr/local holds the bulk of the files installed from the .Xr ports 7 hierarchy and other third party software. If you do not use ports all that much and do not intend to keep system source .Pq Pa /usr/src on the machine, you can get away with a 1 gigabyte .Pa /usr partition. However, if you install a lot of ports (especially window managers and linux-emulated binaries), we recommend at least a 2 gigabyte .Pa /usr partition, and if you also intend to keep system source on the machine, we recommend a 3 gigabyte .Pa /usr partition. Do not underestimate the amount of space you will need in this partition, it can creep up and surprise you! .Pp The .Pa /home partition is typically used to hold user-specific data. Many users simply size it to the remainder of the disk. .Ss SWAP You should typically size your swap space to approximately 2x main memory. If you do not have a lot of RAM, though, you will generally want a lot more swap. It is not recommended that you configure any less than 256M of swap on a system and you should keep in mind future memory expansion when sizing the swap partition. The kernel's VM paging algorithms are tuned to perform best when there is at least 2x swap versus main memory. Configuring too little swap can lead to inefficiencies in the VM page scanning code as well as create issues later on if you add more memory to your machine. .Pp On larger systems with multiple SCSI disks (or multiple IDE disks operating on different controllers), we strongly recommend that you configure swap on each drive (up to four drives). The swap partitions on the drives should be approximately the same size. The kernel can handle arbitrary sizes but internal data structures scale to 4 times the largest swap partition. Keeping the swap partitions near the same size will allow the kernel to optimally stripe swap space across the N disks. Don't worry about overdoing it a little, swap space is the saving grace of .Ux and even if you don't normally use much swap, it can give you more time to recover from a runaway program before being forced to reboot. .Ss NEWFS, TUNEFS AND MOUNT Properly partitioning your system allows you to tune .Xr newfs 8 , and .Xr tunefs 8 parameters. Tuning .Xr newfs 8 requires more experience but can lead to significant improvements in performance. There are three parameters that are relatively safe to tune: .Em blocksize , bytes/inode , and .Em cylinders/group . .Pp .Fx performs best when using 8K or 16K filesystem block sizes. The default filesystem block size is 8K. For larger partitions it is usually a good idea to use a 16K block size. This also requires you to specify a larger fragment size. We recommend always using a fragment size that is 1/8 the block size (less testing has been done on other fragment size factors). The .Xr newfs 8 options for this would be .Dq Li "newfs -f 2048 -b 16384 ..." . Using a larger block size can cause fragmentation of the buffer cache and lead to lower performance. .Pp If a large partition is intended to be used to hold fewer, larger files, such as a database files, you can increase the .Em bytes/inode ratio which reduces the number of inodes (maximum number of files and directories that can be created) for that partition. Decreasing the number of inodes in a filesystem can greatly reduce .Xr fsck 8 recovery times after a crash. Do not use this option unless you are actually storing large files on the partition, because if you overcompensate you can wind up with a filesystem that has lots of free space remaining but cannot accommodate any more files. Using 32768, 65536, or 262144 bytes/inode is recommended. You can go higher but it will have only incremental effects on .Xr fsck 8 recovery times. For example, .Dq Li "newfs -i 32768 ..." . .Pp Finally, increasing the .Em cylinders/group ratio has the effect of packing the inodes closer together. This can increase directory performance and also decrease .Xr fsck 8 times. If you use this option at all, we recommend maxing it out. Use .Dq Li "newfs -c 999" and .Xr newfs 8 will error out and tell you what the maximum is, then use that. .Pp .Xr tunefs 8 may be used to further tune a filesystem. This command can be run in single-user mode without having to reformat the filesystem. However, this is possibly the most abused program in the system. Many people attempt to increase available filesystem space by setting the min-free percentage to 0. This can lead to severe filesystem fragmentation and we do not recommend that you do this. Really the only .Xr tunefs 8 option worthwhile here is turning on .Em softupdates with .Dq Li "tunefs -n enable /filesystem" . (Note: in .Fx 5.x softupdates can be turned on using the .Fl U option to .Xr newfs 8 ) . .Pp A number of run-time .Xr mount 8 options exist that can help you tune the system. The most obvious and most dangerous one is .Cm async . Don't ever use it, it is far too dangerous. A less dangerous and more useful .Xr mount 8 option is called .Cm noatime . .Ux filesystems normally update the last-accessed time of a file or directory whenever it is accessed. This operation is handled in .Fx with a delayed write and normally does not create a burden on the system. However, if your system is accessing a huge number of files on a continuing basis the buffer cache can wind up getting polluted with atime updates, creating a burden on the system. For example, if you are running a heavily loaded web site, or a news server with lots of readers, you might want to consider turning off atime updates on your larger partitions with this .Xr mount 8 option. However, you should not gratuitously turn off atime updates everywhere. For example, the .Pa /var filesystem customarily holds mailboxes, and atime (in combination with mtime) is used to determine whether a mailbox has new mail. You might as well leave atime turned on for mostly read-only partitions such as .Pa / and .Pa /usr as well. This is especially useful for .Pa / since some system utilities use the atime field for reporting. .Ss SOFTUPDATES Softupdates drastically improves meta-data performance, mainly file creation and deletion. We recommend enabling softupdates on all of your filesystems. There are two downsides to softupdates that you should be aware of. First, softupdates guarantees filesystem consistency in the case of a crash but could very easily be several seconds (even a minute!) behind updating the physical disk. If you crash you may lose more work than otherwise. Secondly, softupdates delays the freeing of filesystem blocks. If you have a filesystem (such as the root filesystem) which is close to full, doing a major update of it, e.g.\& .Dq Li "make installworld" , can run it out of space and cause the update to fail. .Pp Softupdates can be turned on using the .Fl U option to .Xr newfs 8 . .Ss STRIPING In larger systems you can stripe partitions from several drives together to create a much larger overall partition. Striping can also improve the performance of a filesystem by splitting I/O operations across two or more disks. The .Xr vinum 8 and .Xr ccdconfig 8 utilities may be used to create simple striped filesystems. Generally speaking, striping smaller partitions such as the root and .Pa /var/tmp , or essentially read-only partitions such as .Pa /usr is a complete waste of time. You should only stripe partitions that require serious I/O performance, typically .Pa /var , /home , or custom partitions used to hold databases and web pages. Choosing the proper stripe size is also important. Filesystems tend to store meta-data on power-of-2 boundaries and you usually want to reduce seeking rather than increase seeking. This means you want to use a large off-center stripe size such as 1152 sectors so sequential I/O does not seek both disks and so meta-data is distributed across both disks rather than concentrated on a single disk. If you really need to get sophisticated, we recommend using a real hardware RAID controller from the list of .Fx supported controllers. .Ss MISC DISK AND FILESYSTEMS Why partition at all? Why not just create one big .Pa / partition and be done with it? Then I don't have to worry about undersizing things! Well, there are several reasons this isn't a good idea. First, each partition has different operational characteristics and separating them allows the filesystem to tune itself to those characteristics. For example, the root and .Pa /usr partitions are read-mostly, with very little writing, while a lot of reading and writing could occur in .Pa /var and .Pa /var/tmp . By properly partitioning your system fragmentation introduced in the smaller more heavily write-loaded partitions will not bleed over into the mostly-read partitions. Additionally, keeping the write-loaded partitions closer to the edge of the disk (i.e. before the really big partitions instead of after in the partition table) will increase I/O performance in the partitions where you need it the most. Now it is true that you might also need I/O performance in the larger partitions, but they are so large that shifting them more towards the edge of the disk will not lead to a significant performance improvement whereas moving .Pa /var to the edge can have a huge impact. Finally, there are safety concerns. Having a small neat root partition that is essentially read-only gives it a greater chance of surviving a bad crash intact. .Sh SYSCTL There are several hundred .Xr sysctl 8 variables in the system, including many that appear to be candidates for tuning but actually aren't. In this document we will only cover the ones that have the greatest effect on the system. .Ss VM AND FILESYSTEM The .Va kern.ipc.shm_use_phys sysctl defaults to 0 (off) and may be set to 0 (off) or 1 (on). Setting this parameter to 1 will cause all System V shared memory segments to be mapped to unpageable physical RAM. This feature only has an effect if you are either (A) mapping small amounts of shared memory across many (hundreds) of processes, or (B) mapping large amounts of shared memory across any number of processes. This feature allows the kernel to remove a great deal of internal memory management page-tracking overhead at the cost of wiring the shared memory into core, making it unswappable. .Pp The .Va vfs.vmiodirenable sysctl defaults to 1 (on). This parameter controls how directories are cached by the system. Most directories are small and use but a single fragment (typically 1K) in the filesystem and even less (typically 512 bytes) in the buffer cache. However, when operating in the default mode the buffer cache will only cache a fixed number of directories even if you have a huge amount of memory. Turning on this sysctl allows the buffer cache to use the VM Page Cache to cache the directories. The advantage is that all of memory is now available for caching directories. The disadvantage is that the minimum in-core memory used to cache a directory is the physical page size (typically 4K) rather than 512 bytes. We recommend turning this option off in memory-constrained environments; however, when on, it will substantially improve the performance of services which manipulate large numbers of files. Such services can include web caches, large mail systems, and news systems. Turning on this option will generally not reduce performance even with the wasted memory but you should experiment to find out. .Pp There are various buffer-cache and VM page cache related sysctls. We do not recommend modifying those values, as of .Fx 4.3 , the VM system does an extremely good job tuning itself. .Pp The .Va kern.maxfiles sysctl determines how many open files the system supports. The default is typically a few thousand but you may need to bump this up to ten or twenty thousand if you are running databases or large descriptor-heavy daemons. .Pp The .Va vm.swap_idle_enabled sysctl is useful in large multi-user systems where you have lots of users entering and leaving the system and lots of idle processes. Such systems tend to generate a great deal of continuous pressure on free memory reserves. Turning this feature on and adjusting the swapout hysteresis (in idle seconds) via .Va vm.swap_idle_threshold1 and .Va vm.swap_idle_threshold2 allows you to depress the priority of pages associated with idle processes more quickly then the normal pageout algorithm. This gives a helping hand to the pageout daemon. Do not turn this option on unless you need it, because the tradeoff you are making is to essentially pre-page memory sooner rather then later, eating more swap and disk bandwidth. In a small system this option will have a detrimental effect but in a large system that is already doing moderate paging this option allows the VM system to stage whole processes into and out of memory more easily. .Ss NETWORKING The .Va net.inet.tcp.sendspace and .Va net.inet.tcp.recvspace sysctls are of particular interest if you are running network intensive applications. This controls the amount of send and receive buffer space allowed for any given TCP connection. The default sending buffer is 32k and the default receiving buffer is 64k. You can often improve bandwidth utilization by increasing the default at the cost of eating up more kernel memory for each connection. We do not recommend increasing the defaults if you are serving hundreds or thousands of simultaneous connections because it is possible to quickly run the system out of memory due to stalled connections building up. But if you need high bandwidth over a fewer number of connections, especially if you have gigabit ethernet, increasing these defaults can make a huge difference. You can adjust the buffer size for incoming and outgoing data separately. For example, if your machine is primarily doing web serving you may want to decrease the recvspace in order to be able to increase the sendspace without eating too much kernel memory. Note that the routing table (see .Xr route 8 ) can be used to introduce route-specific send and receive buffer size defaults. .Pp As an additional management tool you can use pipes in your firewall rules (see .Xr ipfw 8 ) to limit the bandwidth going to or from particular IP blocks or ports. For example, if you have a T1 you might want to limit your web traffic to 70% of the T1's bandwidth in order to leave the remainder available for mail and interactive use. Normally a heavily loaded web server will not introduce significant latencies into other services even if the network link is maxed out, but enforcing a limit can smooth things out and lead to longer term stability. Many people also enforce artificial bandwidth limitations in order to ensure that they are not charged for using too much bandwidth. .Pp Setting the send or receive TCP buffer to values larger then 65535 will result in a marginal performance improvement unless both hosts support the window scaling extension of the TCP protocol, which is controlled by the .Va net.inet.tcp.rfc1323 sysctl. These extensions should be enabled and the TCP buffer size should be set to a value larger than 65536 in order to obtain good performance out of certain types of network links; specifically, gigabit WAN links and high-latency satellite links. .Pp The .Va net.inet.tcp.always_keepalive sysctl determines whether or not the TCP implementation should attempt to detect dead TCP connections by intermittently delivering "keepalives" on the connection. By default this is enabled for all applications, but by setting this sysctl to 0 only applications that specifically request keepalives will use them. In most environments TCP keepalives will improve the management of system state by expiring dead TCP connections, particularly for systems serving dialup users who may not always terminate individual TCP connections before disconnecting from the network. Without the keepalives those connections could remain indefinately. However, in some environments, temporary network outages may be incorrectly identified as dead sessions, resulting in unexpectedly terminated TCP connections. In such environments, setting the sysctl to 0 may reduce the occurrence of TCP session disconnections. A good example of an environment where keepalives may not be wanted is on laptops that are often suspended while maintaining open connections (ssh sessions etc.). While suspended, the laptop would not be able to reply to keepalive requests, and any open connections would eventually be closed, which would be less than optimal. .Pp The .Va kern.ipc.somaxconn sysctl limits the size of the listen queue for accepting new TCP connections. The default value of 128 is typically too low for robust handling of new connections in a heavily loaded web server environment. For such environments, we recommend increasing this value to 1024 or higher. The service daemon may itself limit the listen queue size (e.g.\& .Xr sendmail 8 , apache) but will often have a directive in its configuration file to adjust the queue size up. Larger listen queues also do a better job of fending off denial of service attacks. .Sh LOADER TUNABLES Some aspects of the system behavior may not be tunable at runtime because memory allocations they perform must occur early in the boot process. To change loader tunables, you must set their value in .Xr loader.conf 5 and reboot the system. .Ss DISK .Fx 4.3 flirted with turning off IDE write caching. This reduced write bandwidth to IDE disks but was considered necessary due to serious data consistency issues introduced by hard drive vendors. Basically the problem is that IDE drives lie about when a write completes. With IDE write caching turned on, IDE hard drives will not only write data to disk out of order, they will sometimes delay some of the blocks indefinitely when under heavy disk loads. A crash or power failure can result in serious filesystem corruption. So our default was changed to be safe. Unfortunately, the result was such a huge loss in performance that we caved in and changed the default back to on after the release. You should check the default on your system by observing the .Va hw.ata.wc sysctl variable. If IDE write caching is turned off, you can turn it back on by setting the .Va hw.ata.wc kernel variable back to 1. This must be done from the boot .Xr loader 8 at boot time. Attempting to do it after the kernel boots will have no effect. Please see .Xr ata 4 and .Xr loader 8 . .Pp There is a new experimental feature for IDE hard drives called .Va hw.ata.tags (you also set this in the boot loader) which allows write caching to be safely turned on. This brings SCSI tagging features to IDE drives. As of this writing only IBM DPTA and DTLA drives support the feature. Warning! These drives apparently have quality control problems and we do not recommend purchasing them at this time. If you need performance, we recommend SCSI over IDE. .Ss KERNEL The .Va kern.maxusers tunable defaults to an incredibly low value. For most modern machines, you probably want to increase this value to 64, 128, or 256. We do not recommend going above 256 unless you need a huge number of file descriptors. Network buffers are also affected but can be controlled with a separate kernel option. Do not increase maxusers just to get more network mbufs. Systems older than .Fx 4.4 do not have this loader tunable and require that the kernel .Xr config 8 option .Cd maxusers be set instead. .Pp .Va kern.ipc.nmbclusters may be adjusted to increase the number of network mbufs the system is willing to allocate. Each cluster represents approximately 2K of memory, so a value of 1024 represents 2M of kernel memory reserved for network buffers. You can do a simple calculation to figure out how many you need. If you have a web server which maxes out at 1000 simultaneous connections, and each connection eats a 16K receive and 16K send buffer, you need approximate 32MB worth of network buffers to deal with it. A good rule of thumb is to multiply by 2, so 32MBx2 = 64MB/2K = 32768. So for this case you would want to set .Va kern.ipc.nmbclusters to 32768. We recommend values between 1024 and 4096 for machines with moderates amount of memory, and between 4096 and 32768 for machines with greater amounts of memory. Under no circumstances should you specify an arbitrarily high value for this parameter, it could lead to a boot-time crash. The .Fl m option to .Xr netstat 1 may be used to observe network cluster use. Older versions of .Fx do not have this tunable and require that the kernel .Xr config 8 option .Dv NMBCLUSTERS be set instead. .Pp More and more programs are using the .Xr sendfile 2 system call to transmit files over the network. The .Va kern.ipc.nsfbufs sysctl controls the number of filesystem buffers .Xr sendfile 2 is allowed to use to perform its work. This parameter nominally scales with .Va kern.maxusers so you should not need to modify this parameter except under extreme circumstances. .Sh HARDWARE This section describes items that can be tuned based upon the phyiscal hardware configuration of a machine. .Ss CPU There are a number of compile time options that can affect the performance of .Fx on various processors. Some of the .Dv *_CPU options that can be commented out. If you only want the kernel to run on a Pentium class CPU, you can easily remove .Dv I386_CPU and .Dv I486_CPU , but only remove .Dv I586_CPU if you are sure your CPU is being recognized as a Pentium II or better. Some clones may be recognized as a Pentium or even a 486 and not be able to boot without those options. If it works, great! The operating system will be able to better-use higher-end CPU features for MMU, task switching, timebase, and even device operations. Additionally, higher-end CPUs support 4MB MMU pages which the kernel uses to map the kernel itself into memory, which increases its efficiency under heavy syscall loads. .Pp On SMP machines be sure to enable the .Dv SMP and .Dv APIC_IO options. The .Va kern.smp.active and .Va kern.smp.cpus may also be of interest. .Sh NOTES The type of tuning you do depends heavily on where your system begins to bottleneck as load increases. If your system runs out of CPU (idle times are perpetually 0%) then you need to consider upgrading the CPU or moving to an SMP motherboard (multiple CPU's), or perhaps you need to revisit the programs that are causing the load and try to optimize them. If your system is paging to swap a lot you need to consider adding more memory. If your system is saturating the disk you typically see high CPU idle times and total disk saturation. .Xr systat 1 can be used to monitor this. There are many solutions to saturated disks, for example: increasing memory available for caching, mirroring disks, and distributing operations across several machines. .Pp If disk performance is an issue and you are using IDE drives, switching to SCSI can help a great deal. While modern IDE drives compare with SCSI in raw sequential bandwidth, the moment you start seeking around the disk SCSI drives usually win. .Pp Finally, you might run out of network suds. The first line of defense for improving network performance is to make sure you are using switches instead of hubs, especially these days where switches are almost as cheap. Hubs have severe problems under heavy loads due to collision backoff and one bad host can severely degrade the entire LAN. Second, optimize the network path as much as possible. For example, in .Xr firewall 7 we describe a firewall protecting internal hosts with a topology where the externally visible hosts are not routed through it. Use 100BaseT rather than 10BaseT, or use 1000BaseT rather then 100BaseT, depending on your needs. Most bottlenecks occur at the WAN link (e.g.\& modem, T1, DSL, whatever). If expanding the link is not an option it may be possible to use .Xr dummynet 4 feature to implement peak shaving or other forms of traffic shaping to prevent the overloaded service (such as web services) from affecting other services (such as email), or vice versa. In home installations this could be used to give interactive traffic (your browser, .Xr ssh 1 logins) priority over services you export from your box (web services, email etc.). .Sh SEE ALSO .Xr netstat 1 , .Xr systat 1 , .Xr ata 4 , .Xr dummynet 4 , .Xr login.conf 5 , .Xr firewall 7 , .Xr hier 7 , .Xr ports 7 , .Xr boot 8 , .Xr ccdconfig 8 , .Xr config 8 , .Xr disklabel 8 , .Xr fsck 8 , .Xr ifconfig 8 , .Xr ipfw 8 , .Xr loader 8 , .Xr mount 8 , .Xr newfs 8 , .Xr route 8 , .Xr sysctl 8 , .Xr tunefs 8 , .Xr vinum 8 .Sh HISTORY The .Nm manual page was originally written by .An Matthew Dillon and first appeared in .Fx 4.3 , May 2001. --C7zPtVaVf+AK4Oqc-- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe cvs-all" in the body of the message
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