Re: [RFC/PATCH] perf: Add sizeof operator support

Steven Rostedt
2016-06-17T19:08:32Z

On Fri, 17 Jun 2016 13:57:44 -0500
Jeremy Linton <jeremy.linton@arm.com> wrote:

> That is the simple case, initially I was going to just hand code some of
> the sizeofs in the kernel, but then I started noticing more complex
> cases, and why I RFCed this patch.
>
> For example, on x64/xen there are fair number with sizeof(pXXval_t),
> IIRC I've also seen a fair number of sizeof(struct page *). Some, but I
> dont think all of these case be determined from the field sizes like
> this one:

Right, but there's no easy fix for that. Your patch wont fix these,
because they can change over time.

Now, what we can do is add a sizeof() helper that is like the
TRACE_DEFINE_ENUM() macro. We could add a TRACE_DEFINE_SIZEOF(), that
basically does the same, and in update_event_printk() we could
substitute the sizeof() with the actual number value.

You want to take a crack at that?

Take a look at commit 0c564a538aa93.

-- Steve

>
> [root@X tracing]# cat events/xen/xen_mmu_set_pte/format
> name: xen_mmu_set_pte
> ID: 45
> format:
> field:unsigned short common_type; offset:0; size:2;
> signed:0;
> field:unsigned char common_flags; offset:2; size:1;
> signed:0;
> field:unsigned char common_preempt_count; offset:3;
> size:1; signed:0;
> field:int common_pid; offset:4; size:4; signed:1;
>
> field:pte_t * ptep; offset:8; size:8; signed:0;
> field:pteval_t pteval; offset:16; size:8; signed:0;
>
> print fmt: "ptep %p pteval %0*llx (raw %0*llx)", REC->ptep,
> (int)sizeof(pteval_t) * 2, (unsigned long
> long)pte_val(native_make_pte(REC->pteval)), (int)sizeof(pteval_t) * 2,
> (unsigned long long)REC->pteval
>