From: peterz@infradead.org
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: linux-kernel@vger.kernel.org, io-uring@vger.kernel.org,
Ingo Molnar <mingo@redhat.com>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
Jens Axboe <axboe@kernel.dk>,
Thomas Gleixner <tglx@linutronix.de>
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: <20200819142134.GD2674@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20200819133320.bxwb3ikjswyhmsyg@linutronix.de>
On Wed, Aug 19, 2020 at 03:33:20PM +0200, Sebastian Andrzej Siewior wrote:
> On 2020-08-19 15:15:07 [+0200], peterz@infradead.org 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.
next prev parent 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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