Date: Wed, 23 Oct 2024 19:13:17 -0400 From: gnn <gnn@freebsd.org> To: Vadim Goncharov <vadimnuclight@gmail.com> Cc: Arch <freebsd-arch@freebsd.org> Subject: Re: Building kernels with FPU support? Message-ID: <9BC8F88D-380F-4BC0-B1C7-2657916B13BF@freebsd.org> In-Reply-To: <20241024020534.37003492@nuclight.lan> References: <E37A7972-7FBE-4428-81E1-8DC6D0F67726@freebsd.org> <20241024020534.37003492@nuclight.lan>
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On 23 Oct 2024, at 19:05, Vadim Goncharov wrote: > On Wed, 23 Oct 2024 10:38:12 -0400 > gnn <gnn@freebsd.org> wrote: > >> Howdy, >> >> I am wondering if anyone has tried, lately, to see what effect >> building with FPU support has on overall system performance. I've >> been working with a kernel module that needs this (for reasons I'll >> not go into now) and it occurred to me that the perceived performance >> overhead that caused us to only do fixed point in the kernel may no >> longer be significant. I note that Linux has an option to build >> their kernel with FPU support. >> >> And yes, I know that we have the ability to selectively deal with the >> FPU, from the calls outlined in Section 9 for fpu, but I'm asking the >> more general question of "does it matter?" and "if so, how much?" > > Would be great to have it for e.g. having portions of SQLite in kernel,= > e.g. it's R*Tree module for fast 5-dimensions lookup (like for firewall= > rules) uses floats. Funny you should mention sqlite in the kernel, since that's the exact use= case that started me down this path, and is covered in a paper I've co-a= uthored that's been accepted for publication at a database conference in = 2025. I am sure there are other use cases, we already have this on for the open= ssl module, for example. Best, George
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