HP-UX 11i Release Notes (December 2000)

Programming
Libraries
Chapter 13260
Two defects were fixed in nftw():
• When the FTW_CHDIR option is set, directories are considered
unreadable unless they have both read and execute permissions. (The
old nftw() would try to chdir() into a directory without execute
permissions and then abort the walk with an error).
• When the FTW_CHDIR option is set, a directory object is reported to the
user function before it is chdir()'ed into.
nftw() improvements vary depending on options provided, with the
most significant improvements seen in UNIX95 standard mode with the
FTW_PHYS option not set, or when a very large number of directories exist
in the file tree being traversed.
Documentation Change The ftw (3C) and nftw (3C) manpages have
been updated, particularly with respect tothe two defect fixes and means
of achieving best concurrency in threaded applications.
Other Issues The code size of ftw() and nftw() has increased by
about 40%, but the heap requirements are reduced by 50% or more.
If you relied on the FTW_CHDIR defects which were mentioned above,
there may need to be an application change.
Performance Issues Minimally, you should find that ftw() operates
about 6% faster and nftw() 4% faster. On very large file trees where the
number of tracked inodes is in the tens of thousands or more, the
performance gain of nftw() could be 30% to 40% or more.
Performance Improvements to libc’s malloc(3C)
A new environment variable, _M_CACHE_OPTS, is available to help tune
malloc() performance in kernel-threaded applications. This
environment variable configures a thread-private cache for malloc’ed
blocks. If cache is configured, malloc’ed blocks are placed into a thread's
private cache when free() is called, and may thereafter be allocated
from cache when malloc() is called. Having such a cache potentially
improves speed performance for some kernel-threaded applications, by
reducing mutex contention among threads and by deferring coalescence
of blocks.
The thread-private cache is only available for kernel-threaded
applications, i.e. those linked with the pthread library. The installed
shared pthread library version must be PHCO_19666 or later, or the
application must be statically linked with an archive pthread library