Messages in this thread | | | Date | Tue, 6 Jul 2010 16:12:53 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH 2/2] sched: make sched_param arugment static variables in some sched_setscheduler() caller |
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On Tue, 06 Jul 2010 18:13:58 -0400 Steven Rostedt <rostedt@goodmis.org> wrote:
> On Tue, 2010-07-06 at 09:51 +0900, KOSAKI Motohiro wrote: > > Andrew Morton pointed out almost sched_setscheduler() caller are > > using fixed parameter and it can be converted static. it reduce > > runtume memory waste a bit. > > We are replacing runtime waste with permanent waste?
Confused. kernel/trace/ appears to waste resources by design, so what's the issue?
I don't think this change will cause more waste. It'll consume 4 bytes of .data and will save a little more .text.
> > > > Reported-by: Andrew Morton <akpm@linux-foundation.org> > > Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> > > > > > --- a/kernel/trace/trace_selftest.c > > +++ b/kernel/trace/trace_selftest.c > > @@ -560,7 +560,7 @@ trace_selftest_startup_nop(struct tracer *trace, struct trace_array *tr) > > static int trace_wakeup_test_thread(void *data) > > { > > /* Make this a RT thread, doesn't need to be too high */ > > - struct sched_param param = { .sched_priority = 5 }; > > + static struct sched_param param = { .sched_priority = 5 }; > > struct completion *x = data; > > > > This is a thread that runs on boot up to test the sched_wakeup tracer. > Then it is deleted and all memory is reclaimed. > > Thus, this patch just took memory that was usable at run time and > removed it permanently. > > Please Cc me on all tracing changes.
Well if we're so worried about resource wastage then how about making all boot-time-only text and data reside in __init and __initdata sections rather than hanging around uselessly in memory for ever?
Only that's going to be hard because we went and added pointers into .init.text from .data due to `struct tracer.selftest', which will cause a storm of section mismatch warnings. Doh, should have invoked the selftests from initcalls. That might open the opportunity of running the selftests by modprobing the selftest module, too.
And I _do_ wish the selftest module was modprobeable, rather than this monstrosity:
#ifdef CONFIG_FTRACE_SELFTEST /* Let selftest have access to static functions in this file */ #include "trace_selftest.c" #endif
Really? Who had a tastebudectomy over there? At least call it trace_selftest.inc or something, so poor schmucks don't go scrabbling around wondering "how the hell does this thing get built oh no they didn't really go and #include it did they?"
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