[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <ZiIVVBgaDN4RsroT@kernel.org>
Date: Fri, 19 Apr 2024 09:55:16 +0300
From: Mike Rapoport <rppt@...nel.org>
To: Song Liu <song@...nel.org>
Cc: Mark Rutland <mark.rutland@....com>,
Peter Zijlstra <peterz@...radead.org>, linux-kernel@...r.kernel.org,
Alexandre Ghiti <alexghiti@...osinc.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Bjorn Topel <bjorn@...nel.org>,
Catalin Marinas <catalin.marinas@....com>,
Christophe Leroy <christophe.leroy@...roup.eu>,
"David S. Miller" <davem@...emloft.net>,
Dinh Nguyen <dinguyen@...nel.org>,
Donald Dutile <ddutile@...hat.com>,
Eric Chanudet <echanude@...hat.com>,
Heiko Carstens <hca@...ux.ibm.com>, Helge Deller <deller@....de>,
Huacai Chen <chenhuacai@...nel.org>,
Kent Overstreet <kent.overstreet@...ux.dev>,
Luis Chamberlain <mcgrof@...nel.org>,
Michael Ellerman <mpe@...erman.id.au>,
Nadav Amit <nadav.amit@...il.com>,
Palmer Dabbelt <palmer@...belt.com>,
Puranjay Mohan <puranjay12@...il.com>,
Rick Edgecombe <rick.p.edgecombe@...el.com>,
Russell King <linux@...linux.org.uk>,
Steven Rostedt <rostedt@...dmis.org>,
Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
Thomas Gleixner <tglx@...utronix.de>, Will Deacon <will@...nel.org>,
bpf@...r.kernel.org, linux-arch@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, linux-mips@...r.kernel.org,
linux-mm@...ck.org, linux-modules@...r.kernel.org,
linux-parisc@...r.kernel.org, linux-riscv@...ts.infradead.org,
linux-s390@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
linuxppc-dev@...ts.ozlabs.org, loongarch@...ts.linux.dev,
netdev@...r.kernel.org, sparclinux@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH v4 05/15] mm: introduce execmem_alloc() and execmem_free()
On Thu, Apr 18, 2024 at 02:01:22PM -0700, Song Liu wrote:
> On Thu, Apr 18, 2024 at 10:54 AM Mike Rapoport <rppt@...nel.org> wrote:
> >
> > On Thu, Apr 18, 2024 at 09:13:27AM -0700, Song Liu wrote:
> > > On Thu, Apr 18, 2024 at 8:37 AM Mike Rapoport <rppt@...nel.org> wrote:
> > > > > >
> > > > > > I'm looking at execmem_types more as definition of the consumers, maybe I
> > > > > > should have named the enum execmem_consumer at the first place.
> > > > >
> > > > > I think looking at execmem_type from consumers' point of view adds
> > > > > unnecessary complexity. IIUC, for most (if not all) archs, ftrace, kprobe,
> > > > > and bpf (and maybe also module text) all have the same requirements.
> > > > > Did I miss something?
> > > >
> > > > It's enough to have one architecture with different constrains for kprobes
> > > > and bpf to warrant a type for each.
> > >
> > > AFAICT, some of these constraints can be changed without too much work.
> >
> > But why?
> > I honestly don't understand what are you trying to optimize here. A few
> > lines of initialization in execmem_info?
>
> IIUC, having separate EXECMEM_BPF and EXECMEM_KPROBE makes it
> harder for bpf and kprobe to share the same ROX page. In many use cases,
> a 2MiB page (assuming x86_64) is enough for all BPF, kprobe, ftrace, and
> module text. It is not efficient if we have to allocate separate pages for each
> of these use cases. If this is not a problem, the current approach works.
The caching of large ROX pages does not need to be per type.
In the POC I've posted for caching of large ROX pages on x86 [1], the cache is
global and to make kprobes and bpf use it it's enough to set a flag in
execmem_info.
[1] https://lore.kernel.org/all/20240411160526.2093408-1-rppt@kernel.org
> Thanks,
> Song
--
Sincerely yours,
Mike.
Powered by blists - more mailing lists