mbox series

[0/2] eal/riscv: implement prefetch using zicbop

Message ID 20240530171948.19763-1-daniel.gregory@bytedance.com (mailing list archive)
Headers
Series eal/riscv: implement prefetch using zicbop |

Message

Daniel Gregory May 30, 2024, 5:19 p.m. UTC 
Instructions from RISC-V's Zicbop extension can be used to implement the
rte_prefetch* family of functions. On modern versions of GCC (13.1.0+)
and Clang (17.0.1+), these are emitted by __builtin_prefetch() when the
extension is present.

In order to support older compiler versions, this patchset manually
emits these instructions using inline assembly. To do this, I have added
a new flag, RTE_PREFETCH_WRITE_ARCH_DEFINED, that
(similarly to RTE_WAIT_UNTIL_EQUAL_ARCH_DEFINED) hides the generic
implementation of rte_prefetch*_write.

I am still in the process of acquiring hardware that supports this
extension, so I haven't tested how this affects performance yet.

Daniel Gregory (2):
  eal: add flag to hide generic prefetch_write
  eal/riscv: add support for zicbop extension

 config/riscv/meson.build               |  6 +++
 lib/eal/include/generic/rte_prefetch.h | 47 +++++++++++++--------
 lib/eal/riscv/include/rte_prefetch.h   | 57 ++++++++++++++++++++++++--
 3 files changed, 90 insertions(+), 20 deletions(-)

Comments

David Marchand July 12, 2024, 5:22 p.m. UTC | #1 
Hello,

On Thu, May 30, 2024 at 7:21 PM Daniel Gregory
<daniel.gregory@bytedance.com> wrote:
>
> Instructions from RISC-V's Zicbop extension can be used to implement the
> rte_prefetch* family of functions. On modern versions of GCC (13.1.0+)
> and Clang (17.0.1+), these are emitted by __builtin_prefetch() when the
> extension is present.
>
> In order to support older compiler versions, this patchset manually
> emits these instructions using inline assembly. To do this, I have added
> a new flag, RTE_PREFETCH_WRITE_ARCH_DEFINED, that
> (similarly to RTE_WAIT_UNTIL_EQUAL_ARCH_DEFINED) hides the generic
> implementation of rte_prefetch*_write.
>
> I am still in the process of acquiring hardware that supports this
> extension, so I haven't tested how this affects performance yet.

Let's hope you get such hardware by the next release.
We will need reviews too.

CC: Sachin.