125123 - New semaphore implementation for OS/2

Status: VERIFIED FIXED

(NSPR :: NSPR, defect)

Description

[Mike Kaply [:mkaply]]

In our investigation of performance issues on OS/2, we found that one of the 
biggest impacts to performance was PR_Locking.

What we found is that the OS/2 Mutex semaphore APIs are just too slow.

This bug introduces a new semaphore called a fast RAM semaphore which emulates 
a mutex semaphore using event semaphores.

With this change on 0.9.8, OS/2 actually runs Javascript faster than Windows.

Comment 1

[Mike Kaply [:mkaply]]

Attachment: Changes to _os2.h and os2cv.c

Comment 2

[Mike Kaply [:mkaply]]

Attachment: New OS2VACPP.Asm

New version of OS2VACPP.ASM

This file changed a great deal, so a new version is needed.

Comment 3

[Wan-Teh Chang]

Comment on attachment 69137 [details] [diff] [review]
Changes to _os2.h and os2cv.c

>Index: pr/include/md/_os2.h
>@@ -162,7 +189,11 @@
> };
> 
> struct _MDLock {
>-    HMTX mutex;          /* this is recursive on NT */
>+#ifdef USE_RAMSEM
>+    CRITICAL_SECTION mutex;            /* this is recursive on NT */
>+#else
>+    HMTX mutex;                        /* this is recursive on NT */
>+#endif

Should we edit this comment?  Maybe change "NT" to "OS/2"?

Comment 4

[Wan-Teh Chang]

Comment on attachment 69139 [details]
New OS2VACPP.Asm

r=wtc.

Comment 5

[Wan-Teh Chang]

Chris, could you take care of this bug?  Thanks.

Comment 6

[Julien Pierre]

Are these fastram semaphores safe for use on multi-processor (SMP) systems ? I
have heard conflicting things about them. I do see the LOCK prefix in the code
but I'm still not confident.

The other thing if this code is ever to be ported to Windows is that the ASM
code is written to the _Optlink convention that is unavailable in non-IBM
compilers, so the parameter parsing will have to be rewritten in the ASM code.

Comment 7

[hacker formerly known as [e-mail]]

Patch & new os2vacpp.asm have been checked into the tip & client branch.

Checking in pr/include/md/_os2.h;
/cvsroot/mozilla/nsprpub/pr/include/md/_os2.h,v  <--  _os2.h
new revision: 3.25; previous revision: 3.24
done
Checking in pr/src/md/os2/os2cv.c;
/cvsroot/mozilla/nsprpub/pr/src/md/os2/os2cv.c,v  <--  os2cv.c
new revision: 3.11; previous revision: 3.10
done
Checking in pr/src/md/os2/os2vacpp.asm;
/cvsroot/mozilla/nsprpub/pr/src/md/os2/os2vacpp.asm,v  <--  os2vacpp.asm
new revision: 1.2; previous revision: 1.1
done


Checking in pr/include/md/_os2.h;
/cvsroot/mozilla/nsprpub/pr/include/md/_os2.h,v  <--  _os2.h
new revision: 3.21.2.3; previous revision: 3.21.2.2
done
Checking in pr/src/md/os2/os2cv.c;
/cvsroot/mozilla/nsprpub/pr/src/md/os2/os2cv.c,v  <--  os2cv.c
new revision: 3.8.2.3; previous revision: 3.8.2.2
done
Checking in pr/src/md/os2/os2vacpp.asm;
/cvsroot/mozilla/nsprpub/pr/src/md/os2/os2vacpp.asm,v  <--  os2vacpp.asm
new revision: 1.1.4.1; previous revision: 1.1
done

Comment 8

[Mike Kaply [:mkaply]]

verify, this is in.