expl3-code.tex 的作用是什么？为什么它在 LuaLaTeX 中比其他代码加载时间更长。可以避免这种情况吗？
（“C:/Program Files/MiKTeX 2.9/tex/latex/l3kernel/expl3-code.tex”）
分数维：
\documentclass[11pt]{book}
\RequirePackage{luatex85}
\usepackage[paperwidth=142mm,paperheight=210mm,top=25mm,bottom=20mm,left=17mm,right=22mm]{geometry}
%\usepackage{fontspec}
\usepackage{fancyhdr}
\usepackage{graphicx}
\usepackage{chngcntr}
\usepackage{tocloft}
\usepackage{charter}
\usepackage{polyglossia}
\begin{document}
test
\end{document}
什么叫它..
答案1
polyglossia负载fontspec，负载expl3，负载expl3-code.tex。
texdoc expl3会告诉你关于 的一切expl3。它是内核的一部分LaTeX3，是一组用于编写更复杂程序包的编程约定和工具。或者类似的东西。
终端输出会lualatex告诉您包的加载顺序以及哪个包加载了什么。
我修剪了它以显示序言中发生的事情（在此之前，类文件会加载更多内容，在此之后，文档开头的钩子会加载更多内容）。我还为此输出添加了一些缩进，以便您可以更清楚地看到哪个包在何时由什么加载。
(/usr/share/texlive/texmf-dist/tex/generic/luatex85/luatex85.sty)
(/usr/share/texlive/texmf-dist/tex/latex/geometry/geometry.sty
(/usr/share/texlive/texmf-dist/tex/latex/graphics/keyval.sty)
(/usr/share/texlive/texmf-dist/tex/generic/oberdiek/ifpdf.sty)
(/usr/share/texlive/texmf-dist/tex/generic/oberdiek/ifvtex.sty)
(/usr/share/texlive/texmf-dist/tex/generic/ifxetex/ifxetex.sty)
(/home/dcpurton/texmf/tex/latex/geometry/geometry.cfg))
(/usr/share/texlive/texmf-dist/tex/latex/fancyhdr/fancyhdr.sty)
(/usr/share/texlive/texmf-dist/tex/latex/graphics/graphicx.sty
(/usr/share/texlive/texmf-dist/tex/latex/graphics/graphics.sty
(/usr/share/texlive/texmf-dist/tex/latex/graphics/trig.sty)
(/usr/share/texlive/texmf-dist/tex/latex/graphics-cfg/graphics.cfg)
(/usr/share/texlive/texmf-dist/tex/latex/graphics-def/luatex.def)))
(/usr/share/texlive/texmf-dist/tex/latex/chngcntr/chngcntr.sty)
(/usr/share/texlive/texmf-dist/tex/latex/tocloft/tocloft.sty)
(/usr/share/texlive/texmf-dist/tex/latex/psnfss/charter.sty)
(/usr/share/texlive/texmf-dist/tex/latex/polyglossia/polyglossia.sty
(/usr/share/texlive/texmf-dist/tex/latex/etoolbox/etoolbox.sty)
(/usr/share/texlive/texmf-dist/tex/latex/makecmds/makecmds.sty)
(/usr/share/texlive/texmf-dist/tex/latex/xkeyval/xkeyval.sty
(/usr/share/texlive/texmf-dist/tex/generic/xkeyval/xkeyval.tex
(/usr/share/texlive/texmf-dist/tex/generic/xkeyval/xkvutils.tex)))
(/usr/share/texlive/texmf-dist/tex/latex/fontspec/fontspec.sty
(/usr/share/texlive/texmf-dist/tex/latex/l3kernel/expl3.sty
(/usr/share/texlive/texmf-dist/tex/latex/l3kernel/expl3-code.tex)
(/usr/share/texlive/texmf-dist/tex/latex/l3kernel/l3pdfmode.def))
(/usr/share/texlive/texmf-dist/tex/latex/l3packages/xparse/xparse.sty)
(/usr/share/texlive/texmf-dist/tex/latex/fontspec/fontspec-luatex.sty
(/usr/share/texlive/texmf-dist/tex/latex/base/fontenc.sty
(/usr/share/texlive/texmf-dist/tex/latex/base/tuenc.def))
(/usr/share/texlive/texmf-dist/tex/latex/fontspec/fontspec.cfg)
(load luc: /home/dcpurton/.texlive2017/texmf-var/luatex-cache/generic/fonts/otl/lmromandemi10-regular.luc)
(load luc: /home/dcpurton/.texlive2017/texmf-var/luatex-cache/generic/fonts/otl/lmroman10-italic.luc)))
(/usr/share/texlive/texmf-dist/tex/generic/oberdiek/ifluatex.sty)
(/usr/share/texlive/texmf-dist/tex/luatex/luatexbase/luatexbase.sty
(/usr/share/texlive/texmf-dist/tex/luatex/ctablestack/ctablestack.sty)))
这是每个文件中的行数，这可能很好地表明了为什么expl3-code.tex与其他文件相比处理速度较慢（正如 Ulrike 在上面的评论中指出的那样）。
在我的计算机上（2014 年中期 Macbook Air，运行 Linux），MWE 运行仅需一秒多一点的时间。如果我删除该polyglossia软件包，时间会缩短至不到 0.4 秒。
122 /usr/share/texlive/texmf-dist/tex/generic/luatex85/luatex85.sty
1130 /usr/share/texlive/texmf-dist/tex/latex/geometry/geometry.sty
87 /usr/share/texlive/texmf-dist/tex/latex/graphics/keyval.sty
49 /usr/share/texlive/texmf-dist/tex/generic/oberdiek/ifpdf.sty
261 /usr/share/texlive/texmf-dist/tex/generic/oberdiek/ifvtex.sty
50 /usr/share/texlive/texmf-dist/tex/generic/ifxetex/ifxetex.sty
236 /usr/share/texlive/texmf-dist/tex/latex/fancyhdr/fancyhdr.sty
276 /usr/share/texlive/texmf-dist/tex/latex/graphics/graphicx.sty
521 /usr/share/texlive/texmf-dist/tex/latex/graphics/graphics.sty
117 /usr/share/texlive/texmf-dist/tex/latex/graphics/trig.sty
61 /usr/share/texlive/texmf-dist/tex/latex/graphics-cfg/graphics.cfg
581 /usr/share/texlive/texmf-dist/tex/latex/graphics-def/luatex.def
110 /usr/share/texlive/texmf-dist/tex/latex/chngcntr/chngcntr.sty
1151 /usr/share/texlive/texmf-dist/tex/latex/tocloft/tocloft.sty
31 /usr/share/texlive/texmf-dist/tex/latex/psnfss/charter.sty
871 /usr/share/texlive/texmf-dist/tex/latex/polyglossia/polyglossia.sty
1755 /usr/share/texlive/texmf-dist/tex/latex/etoolbox/etoolbox.sty
95 /usr/share/texlive/texmf-dist/tex/latex/makecmds/makecmds.sty
152 /usr/share/texlive/texmf-dist/tex/latex/xkeyval/xkeyval.sty
622 /usr/share/texlive/texmf-dist/tex/generic/xkeyval/xkeyval.tex
271 /usr/share/texlive/texmf-dist/tex/generic/xkeyval/xkvutils.tex
41 /usr/share/texlive/texmf-dist/tex/latex/fontspec/fontspec.sty
326 /usr/share/texlive/texmf-dist/tex/latex/l3kernel/expl3.sty
23763 /usr/share/texlive/texmf-dist/tex/latex/l3kernel/expl3-code.tex
442 /usr/share/texlive/texmf-dist/tex/latex/l3kernel/l3pdfmode.def
2174 /usr/share/texlive/texmf-dist/tex/latex/l3packages/xparse/xparse.sty
3758 /usr/share/texlive/texmf-dist/tex/latex/fontspec/fontspec-luatex.sty
113 /usr/share/texlive/texmf-dist/tex/latex/base/fontenc.sty
518 /usr/share/texlive/texmf-dist/tex/latex/base/tuenc.def
22 /usr/share/texlive/texmf-dist/tex/latex/fontspec/fontspec.cfg
265 /usr/share/texlive/texmf-dist/tex/generic/oberdiek/ifluatex.sty
301 /usr/share/texlive/texmf-dist/tex/luatex/luatexbase/luatexbase.sty
59 /usr/share/texlive/texmf-dist/tex/luatex/ctablestack/ctablestack.sty