From b1a20253fe8a1f099a23735c9a613b433df67261 Mon Sep 17 00:00:00 2001 From: Than McIntosh Date: Wed, 4 Sep 2019 11:25:06 -0400 Subject: [PATCH] cmd/link: memoize/cache whether plugin.Open symbol available Perform a single lookup of "plugin.Open" at the point where we set the loaded flag for the context, then cache whether the result is nil, so that we can consult this cached value later on (instead of having to look up the symbol each time). This helps speed up the DynLinkingGo() context method, which is called from within some very hot loops in the linker (when linking 'hyperkube' from kubernetes, reduces total calls to "sym.(*Symbols).ROLookup" from 6.5M to 4.3M) Change-Id: I92a2ea2b21d24f67aec0a7afeef4acc77c095adf Reviewed-on: https://go-review.googlesource.com/c/go/+/193260 Reviewed-by: Jeremy Faller Reviewed-by: Cherry Zhang --- src/cmd/link/internal/ld/lib.go | 10 ++++++++-- src/cmd/link/internal/ld/link.go | 1 + 2 files changed, 9 insertions(+), 2 deletions(-) diff --git a/src/cmd/link/internal/ld/lib.go b/src/cmd/link/internal/ld/lib.go index 92dc9ba061..1deab660b7 100644 --- a/src/cmd/link/internal/ld/lib.go +++ b/src/cmd/link/internal/ld/lib.go @@ -173,12 +173,15 @@ func (ctxt *Link) DynlinkingGo() bool { if !ctxt.Loaded { panic("DynlinkingGo called before all symbols loaded") } - return ctxt.BuildMode == BuildModeShared || ctxt.linkShared || ctxt.BuildMode == BuildModePlugin || ctxt.CanUsePlugins() + return ctxt.BuildMode == BuildModeShared || ctxt.linkShared || ctxt.BuildMode == BuildModePlugin || ctxt.canUsePlugins } // CanUsePlugins reports whether a plugins can be used func (ctxt *Link) CanUsePlugins() bool { - return ctxt.Syms.ROLookup("plugin.Open", sym.SymVerABIInternal) != nil + if !ctxt.Loaded { + panic("CanUsePlugins called before all symbols loaded") + } + return ctxt.canUsePlugins } // UseRelro reports whether to make use of "read only relocations" aka @@ -595,6 +598,9 @@ func (ctxt *Link) loadlib() { // We've loaded all the code now. ctxt.Loaded = true + // Record whether we can use plugins. + ctxt.canUsePlugins = (ctxt.Syms.ROLookup("plugin.Open", sym.SymVerABIInternal) != nil) + // If there are no dynamic libraries needed, gcc disables dynamic linking. // Because of this, glibc's dynamic ELF loader occasionally (like in version 2.13) // assumes that a dynamic binary always refers to at least one dynamic library. diff --git a/src/cmd/link/internal/ld/link.go b/src/cmd/link/internal/ld/link.go index d3ffacf54e..dc39f084bf 100644 --- a/src/cmd/link/internal/ld/link.go +++ b/src/cmd/link/internal/ld/link.go @@ -67,6 +67,7 @@ type Link struct { linkShared bool // link against installed Go shared libraries LinkMode LinkMode BuildMode BuildMode + canUsePlugins bool // initialized when Loaded is set to true compressDWARF bool Tlsg *sym.Symbol -- 2.50.0