Call target_can_download_tracepoint if there are tracepoints to download
authorYao Qi <yao.qi@linaro.org>
Thu, 10 Sep 2015 11:31:36 +0000 (12:31 +0100)
committerYao Qi <yao.qi@linaro.org>
Thu, 10 Sep 2015 11:31:36 +0000 (12:31 +0100)
commitdd2e65cc2c48f2fe1343840b610bc6dd4246f35b
tree345dfb8e500b1ef6733a210f258cae266abdd0b1
parent55edd97b4b2fb373e7895c449ff439efb6de1509
Call target_can_download_tracepoint if there are tracepoints to download

Nowadays, GDB calls target_can_download_tracepoint at the entry of
download_tracepoint_locations, which is called by.
update_global_location_list.  Sometimes, it is not needed to call
target_can_download_tracepoint at all because there is no tracepoint
created.  In remote target, target_can_download_tracepoint send
qTStatus to the remote in order to know whether tracepoint can be
downloaded or not.  This means some redundant qTStatus packets are
sent.

This patch is to teach GDB to call target_can_download_tracepoint
lazily, only on the moment there are tracepoint to download.
gdb.perf/single-step.exp (with a local patch to measure RSP packets)
shows the number of RSP packets is reduced because there is no
tracepoint at all, so GDB doesn't send qTStatus any more.

                       # of RSP packets
                       original  patched
single-step rsp 1000   7000      6000
single-step rsp 2000   14000     12000
single-step rsp 3000   21000     18000
single-step rsp 4000   28000     24000

gdb:

2015-09-10  Yao Qi  <yao.qi@linaro.org>

* breakpoint.c (download_tracepoint_locations): New local
can_download_tracepoint.  Check the result of
target_can_download_tracepoint and save it in
can_download_tracepoint if there are tracepoints to download.
* linux-nat.h (enum tribool): Move it to ...
* common/common-types.h: ... here.
gdb/ChangeLog
gdb/breakpoint.c
gdb/common/common-types.h
gdb/linux-nat.h