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From: [email protected]
To: Sebastian Andrzej Siewior <[email protected]>
Cc: [email protected], [email protected],
	Ingo Molnar <[email protected]>,
	Juri Lelli <[email protected]>,
	Vincent Guittot <[email protected]>,
	Dietmar Eggemann <[email protected]>,
	Steven Rostedt <[email protected]>,
	Ben Segall <[email protected]>, Mel Gorman <[email protected]>,
	Jens Axboe <[email protected]>,
	Thomas Gleixner <[email protected]>
Subject: Re: [RFC PATCH] sched: Invoke io_wq_worker_sleeping() with enabled preemption
Date: Wed, 19 Aug 2020 16:21:34 +0200	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

On Wed, Aug 19, 2020 at 03:33:20PM +0200, Sebastian Andrzej Siewior wrote:
> On 2020-08-19 15:15:07 [+0200], [email protected] wrote:

> If you want to optimize further, we could move PF_IO_WORKER to an lower
> bit. x86 can test for both via
> (gcc-10)
> |         testl   $536870944, 44(%rbp)    #, _11->flags
> |         jne     .L1635  #,
> 
> (clang-9)
> |         testl   $536870944, 44(%rbx)    # imm = 0x20000020
> |         je      .LBB112_6
> 
> 
> but ARM can't and does
> |          ldr     r1, [r5, #16]   @ tsk_3->flags, tsk_3->flags
> |         mov     r2, #32 @ tmp157,
> |         movt    r2, 8192        @ tmp157,
> |         tst     r2, r1  @ tmp157, tsk_3->flags
> |         beq     .L998           @,
> 
> same ARM64
> |         ldr     w0, [x20, 60]   //, _11->flags
> |         and     w0, w0, 1073741792      // tmp117, _11->flags,
> |         and     w0, w0, -536870849      // tmp117, tmp117,
> |         cbnz    w0, .L453       // tmp117,
> 
> using 0x10 for PF_IO_WORKER instead will turn this into:
> |         ldr     w0, [x20, 60]   //, _11->flags
> |         tst     w0, 48  // _11->flags,
> |         bne     .L453           //,
> 
> ARM:
> |         ldr     r2, [r5, #16]   @ tsk_3->flags, tsk_3->flags
> |         tst     r2, #48 @ tsk_3->flags,
> |         beq     .L998           @,

Good point, AFAICT there's a number of low bits still open (and we can
shuffle if we have to), so sure put a patch in to that effect while
you're at it.



  reply	other threads:[~2020-08-19 14:22 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-19 12:37 [RFC PATCH] sched: Invoke io_wq_worker_sleeping() with enabled preemption Sebastian Andrzej Siewior
2020-08-19 13:15 ` peterz
2020-08-19 13:18   ` Jens Axboe
2020-08-19 19:44     ` [PATCH] io_wq: Make io_wqe::lock a raw_spinlock_t Sebastian Andrzej Siewior
2020-09-01  8:41       ` [PATCH v2] " Sebastian Andrzej Siewior
2020-09-01 14:17         ` Jens Axboe
2020-08-19 13:33   ` [RFC PATCH] sched: Invoke io_wq_worker_sleeping() with enabled preemption Sebastian Andrzej Siewior
2020-08-19 14:21     ` peterz [this message]
2020-08-19 19:55       ` [PATCH 1/2] sched: Bring the PF_IO_WORKER and PF_WQ_WORKER bits closer together Sebastian Andrzej Siewior
2020-08-19 20:00         ` [PATCH 2/2] sched: Cache task_struct::flags in sched_submit_work() Sebastian Andrzej Siewior
2020-08-19 20:11           ` Peter Zijlstra
2020-09-07 12:58         ` [PATCH 1/2] sched: Bring the PF_IO_WORKER and PF_WQ_WORKER bits closer together Will Deacon

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