From 6526d1676ba5a645f65d751e7529ccd273579017 Mon Sep 17 00:00:00 2001 From: pennae Date: Fri, 4 Mar 2022 19:31:59 +0100 Subject: replace most Pos objects/ptrs with indexes into a position table Pos objects are somewhat wasteful as they duplicate the origin file name and input type for each object. on files that produce more than one Pos when parsed this a sizeable waste of memory (one pointer per Pos). the same goes for ptr on 64 bit machines: parsing enough source to require 8 bytes to locate a position would need at least 8GB of input and 64GB of expression memory. it's not likely that we'll hit that any time soon, so we can use a uint32_t index to locate positions instead. --- src/libexpr/value-to-json.cc | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) (limited to 'src/libexpr/value-to-json.cc') diff --git a/src/libexpr/value-to-json.cc b/src/libexpr/value-to-json.cc index 7b35abca2..307934292 100644 --- a/src/libexpr/value-to-json.cc +++ b/src/libexpr/value-to-json.cc @@ -10,7 +10,7 @@ namespace nix { void printValueAsJSON(EvalState & state, bool strict, - Value & v, const Pos & pos, JSONPlaceholder & out, PathSet & context) + Value & v, const PosIdx pos, JSONPlaceholder & out, PathSet & context) { checkInterrupt(); @@ -54,10 +54,10 @@ void printValueAsJSON(EvalState & state, bool strict, for (auto & j : names) { Attr & a(*v.attrs->find(state.symbols.create(j))); auto placeholder(obj.placeholder(j)); - printValueAsJSON(state, strict, *a.value, *a.pos, placeholder, context); + printValueAsJSON(state, strict, *a.value, a.pos, placeholder, context); } } else - printValueAsJSON(state, strict, *i->value, *i->pos, out, context); + printValueAsJSON(state, strict, *i->value, i->pos, out, context); break; } @@ -82,15 +82,15 @@ void printValueAsJSON(EvalState & state, bool strict, case nFunction: auto e = TypeError({ .msg = hintfmt("cannot convert %1% to JSON", showType(v)), - .errPos = v.determinePos(pos) + .errPos = state.positions[v.determinePos(pos)] }); - e.addTrace(pos, hintfmt("message for the trace")); + e.addTrace(state.positions[pos], hintfmt("message for the trace")); throw e; } } void printValueAsJSON(EvalState & state, bool strict, - Value & v, const Pos & pos, std::ostream & str, PathSet & context) + Value & v, const PosIdx pos, std::ostream & str, PathSet & context) { JSONPlaceholder out(str); printValueAsJSON(state, strict, v, pos, out, context); -- cgit v1.2.3 From 8775be33931ec3b1cad97035ff3d5370a97178a1 Mon Sep 17 00:00:00 2001 From: pennae Date: Sat, 5 Mar 2022 14:40:24 +0100 Subject: store Symbols in a table as well, like positions MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit this slightly increases the amount of memory used for any given symbol, but this increase is more than made up for if the symbol is referenced more than once in the EvalState that holds it. on average every symbol should be referenced at least twice (once to introduce a binding, once to use it), so we expect no increase in memory on average. symbol tables are limited to 2³² entries like position tables, and similar arguments apply to why overflow is not likely: 2³² symbols would require as many string instances (at 24 bytes each) and map entries (at 24 bytes or more each, assuming that the map holds on average at most one item per bucket as the docs say). a full symbol table would require at least 192GB of memory just for symbols, which is well out of reach. (an ofborg eval of nixpks today creates less than a million symbols!) --- src/libexpr/value-to-json.cc | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'src/libexpr/value-to-json.cc') diff --git a/src/libexpr/value-to-json.cc b/src/libexpr/value-to-json.cc index 307934292..68235ad11 100644 --- a/src/libexpr/value-to-json.cc +++ b/src/libexpr/value-to-json.cc @@ -50,7 +50,7 @@ void printValueAsJSON(EvalState & state, bool strict, auto obj(out.object()); StringSet names; for (auto & j : *v.attrs) - names.insert(j.name); + names.emplace(state.symbols[j.name]); for (auto & j : names) { Attr & a(*v.attrs->find(state.symbols.create(j))); auto placeholder(obj.placeholder(j)); -- cgit v1.2.3