From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:35149) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RsiNw-00060i-Oq for qemu-devel@nongnu.org; Wed, 01 Feb 2012 17:10:40 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1RsiNs-00087I-Ib for qemu-devel@nongnu.org; Wed, 01 Feb 2012 17:10:36 -0500 Message-ID: <4F29B853.4070805@codemonkey.ws> Date: Wed, 01 Feb 2012 16:10:27 -0600 From: Anthony Liguori MIME-Version: 1.0 References: <1327108107-16600-1-git-send-email-mdroth@linux.vnet.ibm.com> <1327166033-17922-1-git-send-email-mdroth@linux.vnet.ibm.com> In-Reply-To: <1327166033-17922-1-git-send-email-mdroth@linux.vnet.ibm.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] main-loop: For tools, initialize timers as part of qemu_init_main_loop() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Michael Roth Cc: qemu-trivial@nongnu.org, pbonzini@redhat.com, qemu-devel@nongnu.org On 01/21/2012 11:13 AM, Michael Roth wrote: > In some cases initializing the alarm timers can lead to non-negligable > overhead from programs that link against qemu-tool.o. At least, > setting a max-resolution WinMM alarm timer via mm_start_timer() (the > current default for Windows) can increase the "tick rate" on Windows > OSs and affect frequency scaling, and in the case of tools that run > in guest OSs such has qemu-ga, the impact can be fairly dramatic > (+20%/20% user/sys time on a core 2 processor was observed from an idle > Windows XP guest). > > This patch doesn't address the issue directly (not sure what a good > solution would be for Windows, or what other situations it might be > noticeable), but it at least limits the scope of the issue to programs > that "opt-in" to using the main-loop.c functions by only enabling alarm > timers when qemu_init_main_loop() is called, which is already required > to make use of those facilities, so existing users shouldn't be > affected. > > Signed-off-by: Michael Roth Applied. Thanks. Regards, Anthony Liguori > --- > main-loop.c | 2 +- > main-loop.h | 12 ++++++++++++ > qemu-tool.c | 3 ++- > vl.c | 5 +++++ > 4 files changed, 20 insertions(+), 2 deletions(-) > > diff --git a/main-loop.c b/main-loop.c > index 62d95b9..db23de0 100644 > --- a/main-loop.c > +++ b/main-loop.c > @@ -199,7 +199,7 @@ static int qemu_signal_init(void) > } > #endif > > -int qemu_init_main_loop(void) > +int main_loop_init(void) > { > int ret; > > diff --git a/main-loop.h b/main-loop.h > index f971013..4987041 100644 > --- a/main-loop.h > +++ b/main-loop.h > @@ -41,10 +41,22 @@ > * SIGUSR2, thread signals (SIGFPE, SIGILL, SIGSEGV, SIGBUS) and real-time > * signals if available. Remember that Windows in practice does not have > * signals, though. > + * > + * In the case of QEMU tools, this will also start/initialize timers. > */ > int qemu_init_main_loop(void); > > /** > + * main_loop_init: Initializes main loop > + * > + * Internal (but shared for compatibility reasons) initialization routine > + * for the main loop. This should not be used by applications directly, > + * use qemu_init_main_loop() instead. > + * > + */ > +int main_loop_init(void); > + > +/** > * main_loop_wait: Run one iteration of the main loop. > * > * If @nonblocking is true, poll for events, otherwise suspend until > diff --git a/qemu-tool.c b/qemu-tool.c > index 6b69668..183a583 100644 > --- a/qemu-tool.c > +++ b/qemu-tool.c > @@ -83,11 +83,12 @@ void qemu_clock_warp(QEMUClock *clock) > { > } > > -static void __attribute__((constructor)) init_main_loop(void) > +int qemu_init_main_loop(void) > { > init_clocks(); > init_timer_alarm(); > qemu_clock_enable(vm_clock, false); > + return main_loop_init(); > } > > void slirp_select_fill(int *pnfds, fd_set *readfds, > diff --git a/vl.c b/vl.c > index ba55b35..74a47e6 100644 > --- a/vl.c > +++ b/vl.c > @@ -2136,6 +2136,11 @@ static void free_and_trace(gpointer mem) > free(mem); > } > > +int qemu_init_main_loop(void) > +{ > + return main_loop_init(); > +} > + > int main(int argc, char **argv, char **envp) > { > const char *gdbstub_dev = NULL;