73511 - PORT_Arena code never uses PLArena's freelist

Status: RESOLVED FIXED

(NSS :: Libraries, defect, P1)

Description

[Nelson Bolyard (seldom reads bugmail)]

One of the supposed advantages of using PLArenaPools is that arenas
are recycled in a freelist, thereby making calls to malloc and free
less necessary.  But PORT_FreeArena calls PL_FinishArenaPool as the 
destructor for the arena list, and that function actually frees the 
arenas in the pool, rather than returning them to the free list.  

If NSS wants to actually use the arena free list, PORT_FreeArena
should call PL_FreeArenaPool instead of PL_FinishArenaPool,
but ONLY if PL_ARENAMETER is NOT defined.  

This change might potentially reduce heap lock pressure substantially
but it depends on bug 45343 being fixed first.

Comment 1

[Nelson Bolyard (seldom reads bugmail)]

Setting target to 3.3, but will set to 3.2.1 if there's agreement.

Comment 2

[Nelson Bolyard (seldom reads bugmail)]

This is fixed in NSS 3.2.1 and NSS 3.3 (and later).  
The fix depends on NSPR 4.1.1 and later.  
When NSS 3.2.1 is used with NSPR 4.1.1, it calls 
PL_FreeArenaPool prior to calling PL_FinishArenaPool, 
thereby ensuring that the pool's arena blocks go onto NSPR's
arena free list.  When NSS 3.2.1 is used with older versions 
of NSPR, it does not call PL_FinishArenaPool and causes the 
arena blocks to be freed instead.  This is done because of a
bug in the free list management in older versions of NSPR.