Chapter 6. Tune Performance
sendmail is installed with near-default
settings, it provides excellent email services for most machines. But
when installed to service high loads, high volumes, or high rates,
special tuning becomes a requirement.
What’s New with V8.13
There are a few new items in V8.13 that affect performance tuning. They are described in other chapters but referenced here. In this chapter, we augment some of the knowledge imparted in the third edition of the sendmail book.
RequiresDirfsyncoption (Section 24.1.12 [V8.13]) turns off the
REQUIRES_DIR_FSYNC(3.4.47[3ed]) compile-time macro’s setting at runtime. Turning off directory
fsyncsincreases performance—but at (possibly) increased risk.
SuperSafeoption (24.9.107[3ed]) now accepts a new
PostMiltersetting that delays
fsync( )ing the
dffile until after all Milters have reviewed the message. This improves performance when a great deal of email is rejected by Milters that review the message body.
Timeout.queuereturn.dsn(Section 24.1.15[V8.13]) and
Timeout.queuewarn.dsn(Section 24.1.16 [V8.13]) options have been added. Use them to lower bounce timeouts, and thereby to create less congested queues and increase performance.
Some sites have developed delivery agents that receive messages using SMTP over standard input/output. Such delivery agents use the
P=[LPC]equate (20.5.11[3ed]) to achieve this effect. Beginning with V8.13,
sendmailenables connection caching (24.7.5[3ed]) for such ...