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SubjectRe: v4.16+ seeing many unaligned access in dequeue_task_fair() on IA64
On Wed, Apr 04, 2018 at 09:38:56AM -0700, Luck, Tony wrote:
> On Wed, Apr 04, 2018 at 09:25:13AM +0200, Peter Zijlstra wrote:
> > Right, I remember being careful with that. Which again brings me to the
> > RANDSTRUCT thing, which will mess that up.
>
> No RANDSTRUCT config options set for my build.

Weird though, with or without that patch, my ia64-defconfig gives the
below layout.

$ pahole -EC sched_avg ia64-defconfig/kernel/sched/core.o
die__process_function: tag not supported (INVALID)!
struct sched_avg {
/* typedef u64 */ long long unsigned int last_update_time; /* 0 8 */
/* typedef u64 */ long long unsigned int load_sum; /* 8 8 */
/* typedef u64 */ long long unsigned int runnable_load_sum; /* 16 8 */
/* typedef u32 */ unsigned int util_sum; /* 24 4 */
/* typedef u32 */ unsigned int period_contrib; /* 28 4 */
long unsigned int load_avg; /* 32 8 */
long unsigned int runnable_load_avg; /* 40 8 */
long unsigned int util_avg; /* 48 8 */
struct util_est {
unsigned int enqueued; /* 56 4 */
unsigned int ewma; /* 60 4 */
} util_est; /* 56 8 */
/* --- cacheline 1 boundary (64 bytes) --- */

/* size: 64, cachelines: 1, members: 9 */
};

> > Does the below cure things? It makes absolutely no difference for my
> > x86_64-defconfig build, but it puts more explicit alignment constraints
> > on things.
>
> Yes. That fixes it. No unaligned traps with this patch applied.
>
> Tested-by: Tony Luck <tony.luck@intel.com>

Awesome, I'll go get it merged, even though I don't understand where it
went wobbly.

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