From: Andi Kleen <ak@linux.intel.com>
To: Arvind Sankar <nivedita@alum.mit.edu>
Cc: "Kees Cook" <keescook@chromium.org>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Will Deacon" <will@kernel.org>,
"Nick Desaulniers" <ndesaulniers@google.com>,
"Jian Cai" <jiancai@google.com>,
"Fāng-ruì Sòng" <maskray@google.com>,
"Luis Lozano" <llozano@google.com>,
"Manoj Gupta" <manojgupta@google.com>,
stable@vger.kernel.org,
"Catalin Marinas" <catalin.marinas@arm.com>,
"Mark Rutland" <mark.rutland@arm.com>,
"Ard Biesheuvel" <ardb@kernel.org>,
"Peter Collingbourne" <pcc@google.com>,
"James Morse" <james.morse@arm.com>,
"Borislav Petkov" <bp@suse.de>, "Ingo Molnar" <mingo@redhat.com>,
"Russell King" <linux@armlinux.org.uk>,
"Masahiro Yamada" <masahiroy@kernel.org>,
"Nathan Chancellor" <natechancellor@gmail.com>,
"Arnd Bergmann" <arnd@arndb.de>,
x86@kernel.org, clang-built-linux@googlegroups.com,
linux-arch@vger.kernel.org, linux-efi@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org,
"Michal Marek" <michal.lkml@markovi.net>
Subject: Re: [PATCH v5 13/36] vmlinux.lds.h: add PGO and AutoFDO input sections
Date: Mon, 3 Aug 2020 21:45:32 -0700 [thread overview]
Message-ID: <20200804044532.GC1321588@tassilo.jf.intel.com> (raw)
In-Reply-To: <20200803201525.GA1351390@rani.riverdale.lan>
> Why is that? Both .text and .text.hot have alignment of 2^4 (default
> function alignment on x86) by default, so it doesn't seem like it should
> matter for packing density. Avoiding interspersing cold text among
You may lose part of a cache line on each unit boundary. Linux has
a lot of units, some of them small. All these bytes add up.
It's bad for TLB locality too. Sadly with all the fine grained protection
changes the 2MB coverage is eroding anyways, but this makes it even worse.
> regular/hot text seems like it should be a net win.
>
> That old commit doesn't reference efficiency -- it says there was some
> problem with matching when they were separated out, but there were no
> wildcard section names back then.
It was about efficiency.
-Andi
next prev parent reply other threads:[~2020-08-04 4:45 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20200731230820.1742553-1-keescook@chromium.org>
2020-07-31 23:07 ` [PATCH v5 13/36] vmlinux.lds.h: add PGO and AutoFDO input sections Kees Cook
2020-08-01 3:51 ` Arvind Sankar
2020-08-01 6:18 ` Kees Cook
2020-08-01 17:27 ` Arvind Sankar
2020-08-03 19:05 ` Andi Kleen
2020-08-03 20:15 ` Arvind Sankar
2020-08-04 1:19 ` Fāng-ruì Sòng
2020-08-04 4:45 ` Andi Kleen [this message]
2020-08-04 5:32 ` Fāng-ruì Sòng
2020-08-04 16:06 ` Arvind Sankar
2020-08-21 19:18 ` Kees Cook
2020-08-06 1:24 ` Sasha Levin
2020-08-06 1:28 ` Nick Desaulniers
2020-08-19 23:56 ` Sasha Levin
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