3536 - Enhancements to file I/O

Status: RESOLVED WONTFIX

(NSPR :: NSPR, enhancement, P3)

Description

[gordon]

It would be beneficial if the I/O buffering mechanism controlled thread blocking
within NSPR instead of automatically blocking on all I/O. The benefit would
be immediate I/O call return if the requested data is already buffered and in
RAM. Ideally, the I/O stream/buffer mechanism would buffer at least the amount
of data requested by the previous read to that I/O source.

Under this model, the first I/O request would block and yield control to another
thread, but subsequent requests of the same or smaller size would return
immediately. This is a file ring buffer that I have partially implemented.
However, this needs a global manager so that file coherency can be maintained
across multiple reads/writes to the same open file.

This would be a significant increase in concurrency, which is very low today if
you have a small number of threads.

Comment 1

[gordon]

This enchancement request is based on work in progress by Chris Saari.

Comment 2

[Wan-Teh Chang]

Reassigned the bug to gordon.

Comment 3

[don]

Changed target milestone to M6.

Comment 4

[Steve Dagley]

Offloading some of gordon's doomage

Comment 5

[Terry Weissman]

NSPR now has its own Bugzilla product.  Moving this bug to the NSPR product.

Comment 6

[Steve Dagley]

Added a test to see if the async I/O request has already completed before calling
WaitOnThisThread in macio.c::ReadWriteProc.  In a hand timed test this shaved
approx 2 seconds off apprunner startup time on my Mac (=18.5 sec vs. =20.5
seconds).

Moving to M7 as additional improvments were requested in the bug report.

Comment 7

[Paul MacQuiddy]

phillip gone, removing him from qa contact, sorry for spam

Comment 8

[Steve Dagley]

The world of file I/O in Mozilla is in flux as Necko evolves.  Moving to M17 so
we can re-visit this issue when Necko is more defined.

Comment 9

[Peter Trudelle]

Warren, was this the Mac file i/o perf bug you were looking for?

Comment 10

[Warren Harris]

No. I remember a mail exchange with saari about the jar protocol speeding up mac 
startup time, but I'm not sure if there ever was a bug for it.

Comment 11

[Simon Fraser [no longer active]]

I don't fully understand the proposal here. Can anyone clarify?

Comment 12

[Steve Dagley]

Revisiting old open bugs...  With the impending dropping of support for Mac OS
versions prior to Mac OS X and the move to a mach-o based build when Mac NSPR is
basically BSD *nix NSPR can this bug be retired?

Comment 13

[Steve Dagley]

Per Wan-Teh's agreement closing WONTFIX