This is the mail archive of the
archer@sourceware.org
mailing list for the Archer project.
Re: FYI GDB on-disk .debug cache (mmapcache) [Re: Tasks]
Hi,
On Thu, 07 Aug 2008 01:43:56 +0200, Tom Tromey wrote:
> * Maybe we could play some trick to speed up strcmp_iw_ordered.
But it affects only the CPU usage, not the disk access times.
> Jan> My idea was some on-disk cache, created on-demand in ~/.gdb_cache . There
> Jan> could also be some system-wide rpm debuginfo packages cache created in
> Jan> /usr/lib/debug during rpm %post by `gdb --readnow'.
>
> This is an interesting idea, though I find it a bit hard to reconcile
> with the I/O wait theory. Perhaps we would be reading strictly less
> data.
Yes, I see now that the idea was naive. I expected that with the prepared
memory data image just flushed to disk its reading will be cheap.
Unfortunately lookup_minimal_symbol_by_pc_section_1() does a binary search in
this data etc. so reading this mmap()ed image is still expensive.
> Anyway, I plan to do some more investigation. I'm interested in your
> thoughts.
I would try dwarf2_build_psymtabs_easy() myself now, so far just with the
public symbols (regressing GDB). If it would be fast GCC can provide even
indexes for the static symbols.
Regards,
Jan