From: Gary Guo <gary@garyguo.net>
To: "linux-riscv@lists.infradead.org" <linux-riscv@lists.infradead.org>
Subject: Re: [PATCH v3 4/4] RISC-V: Allow booting kernel from any 4KB aligned address
Date: Mon, 25 Mar 2019 17:35:22 +0000 [thread overview]
Message-ID: <e12f6bc2-c993-1dbf-37b8-9562870806f1@garyguo.net> (raw)
In-Reply-To: <CAAhSdy2je-_=AHPawbV-8cUR0P7WvqDZ5wNdEmDVQkR-a88Eog@mail.gmail.com>
On 25/03/2019 16:16, Anup Patel wrote:
> 1G mappings will give better performance compared 2M mappings.
>
> This will be very useful for performance hungry system with lot of RAM.
>
> This patch selects 1G or 2M mapping at runtime based on load address
> alignment.
>
> Regards,
> Anup
>
Not always the case. In general, if set-associative or direct mapped
TLBs are used, then either
1) separate TLBs are used for different granularities. Usually very few
entries will be there for 1G mappings. E.g. Intel CPU's D-TLB has a
separate array of 1G page TLB which is only 4 entries.
2) a smaller-granularity PTE is "faked" by page walker and inserted into
the TLB. E.g. Intel CPU's I-TLB can't hold 1G entry at all.
In either cases the performance won't differ by much. In fact if 1) is
used there are cases where performance can be negatively impacted by
using larger pages.
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next prev parent reply other threads:[~2019-03-25 17:36 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-25 9:22 [PATCH v3 0/4] Boot RISC-V kernel from any 4KB aligned address Anup Patel
2019-03-25 9:23 ` [PATCH v3 1/4] RISC-V: Add separate defconfig for 32bit systems Anup Patel
2019-03-25 9:23 ` [PATCH v3 2/4] RISC-V: Fix memory reservation in setup_bootmem() Anup Patel
2019-03-25 11:38 ` Christoph Hellwig
2019-03-25 16:13 ` Mike Rapoport
2019-04-24 21:06 ` Palmer Dabbelt
2019-03-25 9:23 ` [PATCH v3 3/4] RISC-V: Remove redundant trampoline page table Anup Patel
2019-03-25 11:38 ` Christoph Hellwig
2019-03-25 9:23 ` [PATCH v3 4/4] RISC-V: Allow booting kernel from any 4KB aligned address Anup Patel
2019-03-25 11:39 ` Christoph Hellwig
2019-03-25 12:42 ` Anup Patel
2019-03-25 14:55 ` Christoph Hellwig
2019-03-25 12:48 ` Anup Patel
2019-03-25 14:59 ` Christoph Hellwig
2019-03-25 16:16 ` Anup Patel
2019-03-25 17:35 ` Gary Guo [this message]
2019-03-26 9:43 ` Anup Patel
2019-03-27 7:54 ` Christoph Hellwig
2019-03-28 7:55 ` Mike Rapoport
2019-03-28 9:52 ` Anup Patel
2019-03-28 10:24 ` Anup Patel
2019-03-28 15:35 Anthony Coulter
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