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[binutils-gdb] Add readahead cache to gdb's vFile:pread
- From: sergiodj+buildbot at redhat dot com
- To: gdb-testers at sourceware dot org
- Date: Fri, 21 Aug 2015 05:41:22 -0400
- Subject: [binutils-gdb] Add readahead cache to gdb's vFile:pread
- Authentication-results: sourceware.org; auth=none
*** TEST RESULTS FOR COMMIT 80152258b9dfe033828e5c5b6dc3252be1ba7a84 ***
Author: Pedro Alves <palves@redhat.com>
Branch: master
Commit: 80152258b9dfe033828e5c5b6dc3252be1ba7a84
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.
- Follow-Ups:
- Failures on Fedora-x86_64-native-extended-gdbserver-m32, branch master
- Failures on Fedora-x86_64-native-gdbserver-m64, branch master
- Failures on Fedora-x86_64-native-extended-gdbserver-m64, branch master
- Failures on AIX-POWER7-plain, branch master
- Failures on Fedora-x86_64-native-gdbserver-m32, branch master
- Failures on Debian-s390x-m64, branch master
- Failures on Fedora-ppc64be-cc-with-index, branch master
- Failures on Fedora-ppc64be-m64, branch master
- Failures on Fedora-ppc64be-native-extended-gdbserver-m64, branch master
- Failures on Debian-i686-native-gdbserver, branch master
- Failures on Fedora-ppc64le-native-gdbserver-m64, branch master
- Failures on Debian-i686-native-extended-gdbserver, branch master
- Failures on Debian-x86_64-native-extended-gdbserver-m64, branch master
- Failures on Fedora-ppc64le-m64, branch master
- Failures on Debian-x86_64-m64, branch master