Good catch Pavel, I missed that part where it calls Index manually even if we
have accelerator tables where we don't need to manually index.
We should modify SymbolFileDWARF::Index() that currently looks like:
void SymbolFileDWARF::Index() {
if (m_indexed)
return;
...
}
To look like:
bool SymbolFileDWARF::HasFullIndex() const {
return m_using_apple_tables;
}
void SymbolFileDWARF::Index() {
if (m_indexed || HasFullIndex())
return;
...
}
SymbolFileDWARF::HasFullIndex() is a new function we need to add. Then as we
update LLDB to handle new accelerator tables, like the new DWARF 5 tables Pavel
is working on getting checked into LLVM and LLDB, we can update
SymbolFileDWARF::HasFullIndex() as needed. This should return the high
performance on systems with full accelerator tables. Let us know if this works.
Greg Clayton
> On Mar 13, 2018, at 2:56 AM, Pavel Labath via lldb-dev
> <[email protected]> wrote:
>
> I would start by looking at https://reviews.llvm.org/D32598
> <https://reviews.llvm.org/D32598>, which adds a bunch of work we do up-front.
> I remember looking at this a while back and not being sure whether all of
> that work is relevant for osx, actually. (I'm specifically thinking of the
> SymbolFileDWARF::Index call, which is done unconditionally, but I think that
> index is unused if we have accelerator tables).
>
> On Mon, 12 Mar 2018 at 21:59, Adrian Prantl via lldb-dev
> <[email protected] <mailto:[email protected]>> wrote:
> If this is a Mac I would recommend to build both lldbs in RelWithDebInfo mode
> and then run them through Instruments and compare the traces. I'd be very
> interested in learning what the cause for the slowdown is.
>
> -- adrian
>
> > On Mar 12, 2018, at 2:57 PM, Timothee Cour <[email protected]
> > <mailto:[email protected]>> wrote:
> >
> > after further inspection it turns out it's a performance regression
> > between llvm 5 and llvm 6:
> >
> > $homebrew_D/Cellar/llvm/5.0.1/lldb -s test_lldb.txt -- prog
> > 8 seconds
> > $homebrew_D/Cellar/llvm/6.0.0/bin/lldb -s test_lldb.txt -- prog
> > 40 seconds
> >
> > cat test_lldb.txt:
> > ```
> > b FOO
> > r
> > bt
> > q
> > ```
> >
> > prog is some binary I'm debugging. It's unfortunately hard to reduce.
> > What are good ways to investigate this?
> >
> >
> >
> > On Mon, Mar 12, 2018 at 1:42 PM, Adrian Prantl <[email protected]
> > <mailto:[email protected]>> wrote:
> >> Have you tried diff'ing your cmake invocation against the on used by
> >> homebrew?
> >>
> >> -- adrian
> >>
> >>> On Mar 9, 2018, at 12:59 AM, Timothee Cour via lldb-dev
> >>> <[email protected] <mailto:[email protected]>> wrote:
> >>>
> >>> while testing out https://github.com/llvm-mirror/lldb/pull/3
> >>> <https://github.com/llvm-mirror/lldb/pull/3> I noticed
> >>> that when I compiled lldb from source (even un-modified from git HEAD)
> >>> it was 5X slower than homebrew lldb or default lldb:
> >>>
> >>> I'm compiling lldb as follows:
> >>> ```
> >>> git clone https://github.com/llvm-mirror/llvm.git
> >>> <https://github.com/llvm-mirror/llvm.git>
> >>> cd llvm/tools
> >>> git clone https://github.com/llvm-mirror/lldb
> >>> <https://github.com/llvm-mirror/lldb>
> >>> ## also, patch in https://github.com/llvm-mirror/lldb/pull/3
> >>> <https://github.com/llvm-mirror/lldb/pull/3>
> >>> git clone https://github.com/llvm-mirror/clang
> >>> <https://github.com/llvm-mirror/clang>
> >>> cd ..
> >>> mkdir build
> >>> cd build
> >>> ccmake .. -G Ninja
> >>> # here I set: CMAKE_BUILD_TYPE Release
> >>> ninja all
> >>> ```
> >>>
> >>> I also tried setting `LLVM_ENABLE_ASSERTIONS OFF` but no difference
> >>>
> >>>
> >>> commands.txt
> >>> ```
> >>> b FOO
> >>> r
> >>> bt
> >>> q
> >>> ```
> >>>
> >>> ./test is some program i have.
> >>>
> >>> ```
> >>> time lldb -s commands.txt -- ./test
> >>> 8 seconds
> >>> time ./build/bin/lldb -s commands.txt -- ./test
> >>> 40 seconds
> >>> ```
> >>> _______________________________________________
> >>> lldb-dev mailing list
> >>> [email protected] <mailto:[email protected]>
> >>> http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev
> >>> <http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev>
> >>
>
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