Hi Martin, > -----Original Message----- > From: [email protected] <[email protected]> On > Behalf Of Moore, Martin > (Linux ERT) > Sent: Thursday, April 15, 2021 5:44 AM > To: Discussion list for crash utility usage, maintenance and development > <[email protected]> > Subject: [Crash-utility] [PATCH] Skip alternate hz calculation in Linux 4.8+ > > In task_init() there is a calculation of machdep->hz based on the value of > cfq_slice_async if the symbol > exists: > > > > if (symbol_exists("cfq_slice_async")) { > > uint cfq_slice_async; > > > > get_symbol_data("cfq_slice_async", sizeof(int), > > &cfq_slice_async); > > > > if (cfq_slice_async) { > > machdep->hz = cfq_slice_async * 25; > > > > if (CRASHDEBUG(2)) > > fprintf(fp, > > "cfq_slice_async exists: setting hz to > %d\n", > > machdep->hz); > > } > > } > > > > However, patch “cfq-iosched: Convert from jiffies to nanoseconds” > (https://patchwork.kernel.org/project/linux-block/patch/[email protected] > /) changed the definition of cfq_slice_async from (HZ / 25) to (NSEC_PER_SEC > / 25). As such, the above > calculation will result in a value of 1000000000 for machdep->hz. In > vmcores where the symbol exists and > has this definition, this causes incorrect results for some calculations. I > have a couple of 4.12 vmcores > in this situation, and in them crash shows the uptime as 3 seconds, which > also throws off the timestamps > in “log -T”. > > > > Fix this by skipping the above code block for kernels 4.8 and above: > >
Thank you for the report and patch, there is another discussion about the HZ calculation [1], but anyway I think we should have this patch. Acked-by: Kazuhito Hagio <[email protected]> Could I have your Signed-off-by: tag? Thanks, Kazu [1] https://listman.redhat.com/archives/crash-utility/2021-April/msg00057.html > > --- task.c.orig 2021-04-14 16:07:52.021137849 -0400 > > +++ task.c 2021-04-14 16:11:03.406626370 -0400 > > @@ -417,7 +417,8 @@ > > > > STRUCT_SIZE_INIT(cputime_t, "cputime_t"); > > > > - if (symbol_exists("cfq_slice_async")) { > > + if ((THIS_KERNEL_VERSION < LINUX(4,8,0)) && > > + symbol_exists("cfq_slice_async")) { > > uint cfq_slice_async; > > > > get_symbol_data("cfq_slice_async", sizeof(int), > > > > > > Martin Moore > Linux Engineering Resolution Team > > HPE Pointnext Services > Hewlett Packard Enterprise > > > > -- Crash-utility mailing list [email protected] https://listman.redhat.com/mailman/listinfo/crash-utility
