84871 - Half of Linux cold start is spent stat()ing components files

Status: RESOLVED INVALID

(Core :: XPCOM, defect)

Description

[Roger Chickering]

I'm playing around with the static build on branch
STATIC_BUILD_20010523_BRANCH.  By playing around with
code reordering and stripping binaries, I've gotten
startup time down to around 18 seconds on reboot.

It turns out according to strace that about half of that 
time is spent calling stat() 4 times on each file in 
dist/bin/components.  Sure enough, these commands:

    ls -lL mozilla/dist/bin/components
    ls -lL mozilla/dist/bin/components
    ls -lL mozilla/dist/bin/components
    ls -lL mozilla/dist/bin/components

Take about 9 seconds to execute on my 1GHz PIII running
RedHat 7.0 (+ new compilers).  Of course almost all of
that time comes from the first run of "ls"; after that
all the info is in the disk cache.

This is all coming from a call to NS_SetupRegistry_1 in
xpfe/bootstrap/nsAppRunner.cpp

I sense an opportunity for performance improvement :-)
Please let me know if you'd like some help.

Thanks!
-Roger

Comment 1

[Roger Chickering]

It turns out that almost all of this time is spent resolving
symlinks.  If I copy all the files to a directory it takes very
little time to stat() all those files.  We still spend about 3.5
seconds in NS_SetupRegistry_1(), but it's doing other stuff now.

Marking this invalid.

-Roger