[Crash-utility] [PATCH] Add alternate HZ calculation using write_expire

[HAGIO KAZUHITO(萩尾 一仁)]

-----Original Message-----
> 在 2021年04月26日 09:37, HAGIO KAZUHITO(萩尾　一仁) 写道:
> > Linux 4.8 and later kernels that contain kernel commit 9a7f38c42c2b
> > ("cfq-iosched: Convert from jiffies to nanoseconds") changed the
> > definition of cfq_slice_async, and it cannot be used to calculate
> > the HZ value.
> >
> > Add alternate HZ calculation using write_expire, which depends on
> > CONFIG_MQ_IOSCHED_DEADLINE or CONFIG_IOSCHED_DEADLINE.
> >
> > Signed-off-by: Kazuhito Hagio <k-hagio-ab at nec.com>
> > ---
> >  task.c | 23 +++++++++++++++++++++++
> >  1 file changed, 23 insertions(+)
> >
> > diff --git a/task.c b/task.c
> > index ce2b55f430e0..36cf259e5d7b 100644
> > --- a/task.c
> > +++ b/task.c
> > @@ -432,6 +432,29 @@ task_init(void)
> >  			    	    "cfq_slice_async exists: setting hz to %d\n",
> >  					machdep->hz);
> >  		}
> > +	} else if ((symbol_exists("dd_init_queue") &&
> > +	    gdb_set_crash_scope(symbol_value("dd_init_queue"), "dd_init_queue")) ||
> > +	    (symbol_exists("deadline_init_queue") &&
> > +	    gdb_set_crash_scope(symbol_value("deadline_init_queue"), "deadline_init_queue"))) {
> > +		char buf[BUFSIZE];
> > +		uint write_expire = 0;
> > +
> > +		open_tmpfile();
> > +		sprintf(buf, "printf \"%%d\", write_expire");
> > +		if (gdb_pass_through(buf, pc->tmpfile, GNU_RETURN_ON_ERROR)) {
> > +			rewind(pc->tmpfile);
> > +			if (fgets(buf, BUFSIZE, pc->tmpfile))
> > +				sscanf(buf, "%d", &write_expire);
> > +		}
> > +		close_tmpfile();
> > +
> > +		if (write_expire) {
> > +			machdep->hz = write_expire / 5;
> > +			if (CRASHDEBUG(2))
> > +				fprintf(fp, "write_expire exists: setting hz to %d\n",
> > +					machdep->hz);
> > +		}
> > +		gdb_set_crash_scope(0, NULL);
> >  	}
> >
> >  	if (VALID_MEMBER(runqueue_arrays))
> >
> 
> Acked-by: Lianbo Jiang <lijiang at redhat.com>

Thanks, applied.
https://github.com/crash-utility/crash/commit/b93027ce5c756764978271c71f6612aeb38f8972

Kazu