From: "hch@infradead.org" <hch@infradead.org>
To: Atish Patra <Atish.Patra@wdc.com>
Cc: "aou@eecs.berkeley.edu" <aou@eecs.berkeley.edu>,
"anup@brainfault.org" <anup@brainfault.org>,
"palmer@sifive.com" <palmer@sifive.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"hch@infradead.org" <hch@infradead.org>,
"schwab@linux-m68k.org" <schwab@linux-m68k.org>,
"paul.walmsley@sifive.com" <paul.walmsley@sifive.com>,
"linux-riscv@lists.infradead.org"
<linux-riscv@lists.infradead.org>,
"allison@lohutok.net" <allison@lohutok.net>
Subject: Re: [v2 PATCH] RISC-V: Optimize tlb flush path.
Date: Tue, 20 Aug 2019 02:22:07 -0700 [thread overview]
Message-ID: <20190820092207.GA26271@infradead.org> (raw)
In-Reply-To: <b2510462b55ffd93dba0c1b7cc28f9eef3089b50.camel@wdc.com>
On Tue, Aug 20, 2019 at 08:42:19AM +0000, Atish Patra wrote:
> cmask NULL is pretty common case and we would be unnecessarily
> executing bunch of instructions everytime while not saving much. Kernel
> still have to make an SBI call and OpenSBI is doing a local flush
> anyways.
>
> Looking at the code again, I think we can just use cpumask_weight and
> do local tlb flush only if local cpu is the only cpu present.
>
> Otherwise, it will just fall through and call sbi_remote_sfence_vma().
Maybe it is just time to split the different cases at a higher level.
The idea to multiple everything onto a single function always seemed
odd to me.
FYI, here is what I do for the IPI based tlbflush for the native S-mode
clint prototype, which seems much easier to understand:
http://git.infradead.org/users/hch/riscv.git/commitdiff/ea4067ae61e20fcfcf46a6f6bd1cc25710ce3afe
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WARNING: multiple messages have this Message-ID (diff)
From: "hch@infradead.org" <hch@infradead.org>
To: Atish Patra <Atish.Patra@wdc.com>
Cc: "schwab@linux-m68k.org" <schwab@linux-m68k.org>,
"linux-riscv@lists.infradead.org"
<linux-riscv@lists.infradead.org>,
"paul.walmsley@sifive.com" <paul.walmsley@sifive.com>,
"aou@eecs.berkeley.edu" <aou@eecs.berkeley.edu>,
"allison@lohutok.net" <allison@lohutok.net>,
"anup@brainfault.org" <anup@brainfault.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"hch@infradead.org" <hch@infradead.org>,
"palmer@sifive.com" <palmer@sifive.com>
Subject: Re: [v2 PATCH] RISC-V: Optimize tlb flush path.
Date: Tue, 20 Aug 2019 02:22:07 -0700 [thread overview]
Message-ID: <20190820092207.GA26271@infradead.org> (raw)
In-Reply-To: <b2510462b55ffd93dba0c1b7cc28f9eef3089b50.camel@wdc.com>
On Tue, Aug 20, 2019 at 08:42:19AM +0000, Atish Patra wrote:
> cmask NULL is pretty common case and we would be unnecessarily
> executing bunch of instructions everytime while not saving much. Kernel
> still have to make an SBI call and OpenSBI is doing a local flush
> anyways.
>
> Looking at the code again, I think we can just use cpumask_weight and
> do local tlb flush only if local cpu is the only cpu present.
>
> Otherwise, it will just fall through and call sbi_remote_sfence_vma().
Maybe it is just time to split the different cases at a higher level.
The idea to multiple everything onto a single function always seemed
odd to me.
FYI, here is what I do for the IPI based tlbflush for the native S-mode
clint prototype, which seems much easier to understand:
http://git.infradead.org/users/hch/riscv.git/commitdiff/ea4067ae61e20fcfcf46a6f6bd1cc25710ce3afe
next prev parent reply other threads:[~2019-08-20 9:22 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-20 0:47 [v2 PATCH] RISC-V: Optimize tlb flush path Atish Patra
2019-08-20 0:47 ` Atish Patra
2019-08-20 3:06 ` hch
2019-08-20 3:06 ` hch
2019-08-20 7:14 ` Andreas Schwab
2019-08-20 7:14 ` Andreas Schwab
2019-08-20 7:16 ` hch
2019-08-20 7:16 ` hch
2019-08-20 7:46 ` Andreas Schwab
2019-08-20 7:46 ` Andreas Schwab
2019-08-20 8:42 ` Atish Patra
2019-08-20 8:42 ` Atish Patra
2019-08-20 8:51 ` Andreas Schwab
2019-08-20 8:51 ` Andreas Schwab
2019-08-20 9:22 ` hch [this message]
2019-08-20 9:22 ` hch
2019-08-20 20:28 ` Atish Patra
2019-08-20 20:28 ` Atish Patra
2019-08-20 22:18 ` hch
2019-08-20 22:18 ` hch
2019-08-20 22:24 ` Atish Patra
2019-08-20 22:24 ` Atish Patra
2019-08-21 1:29 ` Alan Kao
2019-08-21 1:29 ` Alan Kao
2019-08-21 1:40 ` hch
2019-08-21 1:40 ` hch
2019-08-21 3:52 ` Anup Patel
2019-08-21 3:52 ` Anup Patel
2019-08-21 7:18 ` hch
2019-08-21 7:18 ` hch
2019-08-20 8:51 ` Anup Patel
2019-08-20 8:51 ` Anup Patel
2019-08-20 20:29 ` Atish Patra
2019-08-20 20:29 ` Atish Patra
2019-08-21 14:41 ` hch
2019-08-21 14:41 ` hch
2019-08-21 14:45 ` hch
2019-08-21 14:45 ` hch
2019-08-21 17:36 ` Atish Patra
2019-08-21 17:36 ` Atish Patra
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