From 0a84137c4512e0a31802e94de7795e04f8ee2198 Mon Sep 17 00:00:00 2001 From: Eelco Dolstra Date: Thu, 21 Feb 2008 12:01:24 +0000 Subject: [PATCH] * checkVarDefs: don't check in closed terms, which don't have undefined variables by definition. This matters for the implementation of "with", which does a call to checkVarDefs to see if the body of the with has no undefined variables. (It can't be checked at parse time because you don't know which variables are in the "with" attribute set.) If we check closed terms, then we check not just the with body but also the substituted terms, which are typically very large. This is the cause of the poor nix-env performance on Nixpkgs lately. It didn't happen earlier because "with" wasn't used very often in the past. This fix improves nix-env performance roughly 60x on current Nixpkgs. nix-env -qa is down from 29.3s to 0.5s on my laptop, and nix-env -qa --out-path is down from 229s to 3.39s. Not bad for a 1-line fix :-) --- src/libexpr/nixexpr.cc | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/src/libexpr/nixexpr.cc b/src/libexpr/nixexpr.cc index 123513594..1eeec2cf1 100644 --- a/src/libexpr/nixexpr.cc +++ b/src/libexpr/nixexpr.cc @@ -215,7 +215,11 @@ static void checkVarDefs2(set & done, const ATermMap & defs, Expr e) ATerm with, body; ATermList rbnds, nrbnds; - if (matchVar(e, name)) { + /* Closed terms don't have free variables, so we don't have to + check by definition. */ + if (matchClosed(e, value)) return; + + else if (matchVar(e, name)) { if (!defs.get(name)) throw EvalError(format("undefined variable `%1%'") % aterm2String(name));