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From: "hch@lst.de" <hch@lst.de>
To: Atish Patra <Atish.Patra@wdc.com>
Cc: "linux-riscv@lists.infradead.org"
	<linux-riscv@lists.infradead.org>,
	"palmer@sifive.com" <palmer@sifive.com>,
	"hch@lst.de" <hch@lst.de>,
	"paul.walmsley@sifive.com" <paul.walmsley@sifive.com>
Subject: Re: [PATCH 3/6] riscv: optimize send_ipi_single
Date: Mon, 26 Aug 2019 13:29:37 +0200	[thread overview]
Message-ID: <20190826112937.GB15002@lst.de> (raw)
In-Reply-To: <570f358ed76092a4072b5acedd4ddb34c318ff9b.camel@wdc.com>

On Sat, Aug 24, 2019 at 12:26:26AM +0000, Atish Patra wrote:
> >  static void send_ipi_single(int cpu, enum ipi_message_type op)
> >  {
> > -	send_ipi_mask(cpumask_of(cpu), op);
> > +	int hartid = cpuid_to_hartid_map(cpu);
> > +
> > +	smp_mb__before_atomic();
> > +	set_bit(op, &ipi_data[cpu].bits);
> > +	smp_mb__after_atomic();
> > +
> > +	sbi_send_ipi(cpumask_bits(cpumask_of(hartid)));
> 
> The only cost save I see is you don't have to cpumask_clear anymore.
> Is there any other cost save ? If not is it worth duplicating the code
> ?
> 
> May be I am being too pedantic here.. :) :)

It avoids the additional potentially huge cpumask, and generally makes
the code a lot more obvious.  This might not really be needed, but
helps with sharing the code nicely with the native IPI path.

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  reply	other threads:[~2019-08-26 11:29 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-21 14:58 misc riscv cleanups Christoph Hellwig
2019-08-21 14:58 ` [PATCH 1/6] riscv: refactor the IPI code Christoph Hellwig
2019-08-24  1:03   ` Atish Patra
2019-09-05  8:44   ` Paul Walmsley
2019-08-21 14:58 ` [PATCH 2/6] riscv: cleanup send_ipi_mask Christoph Hellwig
2019-08-24  0:11   ` Atish Patra
2019-08-26 11:28     ` hch
2019-08-27 18:45       ` Atish Patra
2019-09-05  8:46   ` Paul Walmsley
2019-08-21 14:58 ` [PATCH 3/6] riscv: optimize send_ipi_single Christoph Hellwig
2019-08-24  0:26   ` Atish Patra
2019-08-26 11:29     ` hch [this message]
2019-08-27 18:48       ` Atish Patra
2019-09-05  8:48   ` Paul Walmsley
2019-08-21 14:58 ` [PATCH 4/6] riscv: cleanup riscv_cpuid_to_hartid_mask Christoph Hellwig
2019-08-24  0:03   ` Atish Patra
2019-09-05  8:50   ` Paul Walmsley
2019-08-21 14:58 ` [PATCH 5/6] riscv: don't use the rdtime(h) pseudo-instructions Christoph Hellwig
2019-08-24  0:37   ` Atish Patra
2019-08-24  0:43     ` Atish Patra
2019-08-26 11:30     ` hch
2019-08-27 18:50       ` Atish Patra
2019-09-05  8:55   ` Paul Walmsley
2019-08-21 14:58 ` [PATCH 6/6] riscv: move the TLB flush logic out of line Christoph Hellwig
2019-08-24  0:03   ` Atish Patra
2019-09-05  8:58   ` Paul Walmsley

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