devenv: allow environment total size of up to 1MB

Sometimes, there is the one-off occation when one needs to
pass a huge list in rc...

This change makes devenv track total memory consumption
of environment groups allowing them to grow up to 1MB in
size (including overhead).

(Before, only the variable size was restricted, but
not the amount of files being created).

The maximum value size of a single environment variable
is set to half of the total size, which allows the
occational large value. (But not many of them).

Because we track all memory consuption, it is also
now possible to create around 10k small environment
variales.

A hashtable is added for name lookups and the qid.path
was changed to allow direct indexing into the entry
array without needing a scan lookup.

All smalloc() calls have been removed, exhaustion is
handled with error(Enomem) avoiding deadlock
in case we run out of kernel memory.

1 files changed, 19 insertions, 13 deletions

diff --git a/sys/src/9/port/portdat.h b/sys/src/9/port/portdat.h
index 5bb641f7f..421f673e6 100644
--- a/sys/src/9/port/portdat.h
+++ b/sys/src/9/port/portdat.h
@@ -456,6 +456,8 @@ enum
 	NFD =		100,		/* per process file descriptors */
 	PGHLOG  =	9,
 	PGHSIZE	=	1<<PGHLOG,	/* Page hash for image lookup */
+	ENVLOG =	5,
+	ENVHASH =	1<<ENVLOG,	/* Egrp hash for variable lookup */
 };
 #define REND(p,s)	((p)->rendhash[(s)&((1<<RENDLOG)-1)])
 #define MOUNTH(p,qid)	((p)->mnthash[(qid).path&((1<<MNTLOG)-1)])
@@ -493,23 +495,27 @@ struct Rgrp
 	Proc	*rendhash[RENDHASH];	/* Rendezvous tag hash */
 };
 
-struct Egrp
-{
-	Ref;
-	RWlock;
-	Evalue	*ent;
-	int	nent;
-	int	ment;
-	ulong	path;	/* qid.path of next Evalue to be allocated */
-	ulong	vers;	/* of Egrp */
-};
-
 struct Evalue
 {
-	char	*name;
 	char	*value;
 	int	len;
-	Qid	qid;
+	ulong	vers;
+	uvlong	path;			/* qid.path: Egrp.path << 32 | index (of Egrp.ent[]) */
+	Evalue	*hash;
+	char	name[];
+};
+
+struct Egrp
+{
+	Ref;
+	RWlock;
+	Evalue	**ent;
+	int	nent;			/* numer of slots in ent[] */
+	int	low;			/* lowest free index in ent[] */
+	int	alloc;			/* bytes allocated for env */
+	ulong	path;			/* generator for qid path */
+	ulong	vers;			/* of Egrp */
+	Evalue	*hash[ENVHASH];		/* hashtable for name lookup */
 };
 
 struct Fgrp