<div dir="ltr"><br><div class="gmail_extra"><br><div class="gmail_quote">On Mon, Mar 16, 2015 at 8:29 PM, Shankar Easwaran <span dir="ltr"><<a href="mailto:shankare@codeaurora.org" target="_blank">shankare@codeaurora.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">Author: shankare<br>
Date: Mon Mar 16 22:29:32 2015<br>
New Revision: 232460<br>
<br>
URL: <a href="http://llvm.org/viewvc/llvm-project?rev=232460&view=rev" target="_blank">http://llvm.org/viewvc/llvm-project?rev=232460&view=rev</a><br>
Log:<br>
[ELF] Use parallel_for_each for writing.<br>
<br>
This changes improves performance of lld, when self-hosting lld, when compared<br>
with the bfd linker. BFD linker on average takes 8 seconds in elapsed time.<br>
lld takes 3 seconds elapased time average. Without this change, lld takes ~5<br>
seconds average. The runtime comparisons were done on a release build and<br>
measured by running linking thrice.<br>
<br>
lld self-host without the change<br>
----------------------------------<br>
real 0m3.196s<br>
user 0m4.580s<br>
sys 0m0.832s<br>
<br>
lld self-host with lld<br>
-----------------------<br>
user 0m3.024s<br>
user 0m3.252s<br>
sys 0m0.796s<br>
<br>
time taken to build lld with bfd<br>
--------------------------------<br>
real 0m8.419s<br>
user 0m7.748s<br>
sys 0m0.632s<br>
<br>
Modified:<br>
lld/trunk/lib/ReaderWriter/ELF/OutputELFWriter.h<br>
lld/trunk/lib/ReaderWriter/ELF/SectionChunks.h<br>
<br>
Modified: lld/trunk/lib/ReaderWriter/ELF/OutputELFWriter.h<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/ELF/OutputELFWriter.h?rev=232460&r1=232459&r2=232460&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/ELF/OutputELFWriter.h?rev=232460&r1=232459&r2=232460&view=diff</a><br>
==============================================================================<br>
--- lld/trunk/lib/ReaderWriter/ELF/OutputELFWriter.h (original)<br>
+++ lld/trunk/lib/ReaderWriter/ELF/OutputELFWriter.h Mon Mar 16 22:29:32 2015<br>
@@ -586,8 +586,10 @@ std::error_code OutputELFWriter<ELFT>::w<br>
_elfHeader->write(this, _layout, *buffer);<br>
_programHeader->write(this, _layout, *buffer);<br>
<br>
- for (auto section : _layout.sections())<br>
- section->write(this, _layout, *buffer);<br>
+ auto sections = _layout.sections();<br>
+ parallel_for_each(<br>
+ sections.begin(), sections.end(),<br>
+ [&](Chunk<ELFT> *section) { section->write(this, _layout, *buffer); });<br>
writeTask.end();<br>
<br>
ScopedTask commitTask(getDefaultDomain(), "ELF Writer commit to disk");<br>
<br>
Modified: lld/trunk/lib/ReaderWriter/ELF/SectionChunks.h<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/ELF/SectionChunks.h?rev=232460&r1=232459&r2=232460&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/ELF/SectionChunks.h?rev=232460&r1=232459&r2=232460&view=diff</a><br>
==============================================================================<br>
--- lld/trunk/lib/ReaderWriter/ELF/SectionChunks.h (original)<br>
+++ lld/trunk/lib/ReaderWriter/ELF/SectionChunks.h Mon Mar 16 22:29:32 2015<br>
@@ -234,17 +234,17 @@ public:<br>
/// routine gets called after the linker fixes up the virtual address<br>
/// of the section<br>
virtual void assignVirtualAddress(uint64_t addr) override {<br>
- for (auto &ai : _atoms) {<br>
+ parallel_for_each(_atoms.begin(), _atoms.end(), [&](AtomLayout *ai) {<br>
ai->_virtualAddr = addr + ai->_fileOffset;<br>
- }<br>
+ });<br>
}<br>
<br>
/// \brief Set the file offset of each Atom in the section. This routine<br>
/// gets called after the linker fixes up the section offset<br>
void assignFileOffsets(uint64_t offset) override {<br>
- for (auto &ai : _atoms) {<br>
+ parallel_for_each(_atoms.begin(), _atoms.end(), [&](AtomLayout *ai) {<br>
ai->_fileOffset = offset + ai->_fileOffset;<br>
- }<br>
+ });<br>
}<br>
<br></blockquote><div><br></div><div>It looks like we only ever do `_atoms.push_back(new (_alloc) lld::AtomLayout(...));` can we just store the AtomLayout's by value in the vector? It seems like that would be simpler and also make these loops a lot more cache friendly.</div><div><br></div><div>-- Sean Silva</div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
/// \brief Find the Atom address given a name, this is needed to properly<br>
<br>
<br>
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</blockquote></div><br></div></div>