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Pedro Alves 80152258b9 Add readahead cache to gdb's vFile:pread
This patch almost halves the time it takes to "target remote + run to
main" on a higher-latency connection.

E.g., I've got a ping time of ~85ms to an x86-64 machine on the gcc
compile farm (almost 2000km away from me), and I'm behind a ~16Mbit
ADSL.  When I connect to a gdbserver debugging itself on that machine
and run to main, it takes almost 55 seconds:

 [palves@gcc76] $ ./gdbserver :9999 ./gdbserver
 [palves@home] $ ssh -L 9999:localhost:9999 gcc76.fsffrance.org
 [palves@home] $ time ./gdb -data-directory=data-directory -ex "tar rem :9999" -ex "b main" -ex "c" -ex "set confirm off" -ex "quit"

 Pristine gdb 7.10.50.20150820-cvs gets us:
 ...
 Remote debugging using :9999
 Reading symbols from target:/home/palves/gdb/build/gdb/gdbserver/gdbserver...done.
 Reading symbols from target:/lib64/ld-linux-x86-64.so.2...(no debugging symbols found)...done.
 0x00007ffff7ddd190 in ?? () from target:/lib64/ld-linux-x86-64.so.2
 Breakpoint 1 at 0x41200c: file ../../../src/gdb/gdbserver/server.c, line 3635.
 Continuing.

 Breakpoint 1, main (argc=1, argv=0x7fffffffe3d8) at ../../../src/gdb/gdbserver/server.c:3635
 3635    ../../../src/gdb/gdbserver/server.c: No such file or directory.
 /home/palves/gdb/build/gdb/gdbserver/gdbserver: No such file or directory.

 real    0m54.803s
 user    0m0.329s
 sys     0m0.064s

While with the readahead cache added by this patch, it drops to:

 real    0m29.462s
 user    0m0.454s
 sys     0m0.054s

I added a few counters to show cache hit/miss, and got:

 readahead cache miss 142
 readahead cache hit 310

Tested on x86_64 Fedora 20.

gdb/ChangeLog:
2015-08-21  Pedro Alves  <palves@redhat.com>

	* remote.c (struct readahead_cache): New.
	(struct remote_state) <readahead_cache>: New field.
	(remote_open_1): Invalidate the cache.
	(readahead_cache_invalidate, readahead_cache_invalidate_fd): New
	functions.
	(remote_hostio_pwrite): Invalidate the readahead cache.
	(remote_hostio_pread): Rename to ...
	(remote_hostio_pread_vFile): ... this.
	(remote_hostio_pread_from_cache): New function.
	(remote_hostio_pread): Reimplement.
	(remote_hostio_close): Invalidate the readahead cache.
2015-08-21 10:13:27 +01:00
bfd Automatic date update in version.in 2015-08-21 00:00:07 +00:00
binutils Regen binutils/configure 2015-08-17 12:07:12 +09:30
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gas [AArch64][5/6] GAS support TLSLD load/store relocation types 2015-08-19 16:54:39 +01:00
gdb Add readahead cache to gdb's vFile:pread 2015-08-21 10:13:27 +01:00
gold gold --emit-relocs 2015-08-20 12:02:45 +09:30
gprof
include [AArch64][3/6] GAS support TLSLD move/add relocation types 2015-08-19 16:36:22 +01:00
intl
ld [AArch64][6/6] LD support TLSLD load/store relocation types 2015-08-19 16:57:38 +01:00
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		   README for GNU development tools

This directory contains various GNU compilers, assemblers, linkers, 
debuggers, etc., plus their support routines, definitions, and documentation.

If you are receiving this as part of a GDB release, see the file gdb/README.
If with a binutils release, see binutils/README;  if with a libg++ release,
see libg++/README, etc.  That'll give you info about this
package -- supported targets, how to use it, how to report bugs, etc.

It is now possible to automatically configure and build a variety of
tools with one command.  To build all of the tools contained herein,
run the ``configure'' script here, e.g.:

	./configure 
	make

To install them (by default in /usr/local/bin, /usr/local/lib, etc),
then do:
	make install

(If the configure script can't determine your type of computer, give it
the name as an argument, for instance ``./configure sun4''.  You can
use the script ``config.sub'' to test whether a name is recognized; if
it is, config.sub translates it to a triplet specifying CPU, vendor,
and OS.)

If you have more than one compiler on your system, it is often best to
explicitly set CC in the environment before running configure, and to
also set CC when running make.  For example (assuming sh/bash/ksh):

	CC=gcc ./configure
	make

A similar example using csh:

	setenv CC gcc
	./configure
	make

Much of the code and documentation enclosed is copyright by
the Free Software Foundation, Inc.  See the file COPYING or
COPYING.LIB in the various directories, for a description of the
GNU General Public License terms under which you can copy the files.

REPORTING BUGS: Again, see gdb/README, binutils/README, etc., for info
on where and how to report problems.