archive mirror
 help / color / mirror / Atom feed
From: Rick Edgecombe <>
Cc:,,,,,, Rick Edgecombe <>
Subject: [RFC 0/3] Group pages on the direct map for permissioned vmallocs
Date: Mon,  5 Apr 2021 13:37:08 -0700	[thread overview]
Message-ID: <> (raw)


This is a followup to the previous attempt to overhaul how vmalloc permissions
are done:

In working on a next version it dawned on me that we can significantly reduce
direct map breakage on x86 with a much less invasive change, so I thought maybe
I would start there in the meantime.

In a test of booting fedora and running the BPF unit tests, this reduced 4k
direct map pages by 98%.

It simply uses pages for x86 module_alloc() mappings from a cache created out of
2MB pages. This results in all the later breakage clustering in 2MB blocks on
the direct map. The trade-off is colder pages are used for these allocations.
All module_alloc() users (modules, ebpf jit, ftrace, kprobes) get this behavior.

Potentially this behavior should be enabled for eBPF byte code allocations as
well in the case of !CONFIG_BPF_JIT_ALWAYS_ON.

The new APIs and invasive changes in the callers can happen after vmalloc huge
pages bring more benefits. Although, I can post shootdown reduction changes with
previous comments integrated if anyone disagrees.

Based on v5.11.



Rick Edgecombe (3):
  list: Support getting most recent element in list_lru
  vmalloc: Support grouped page allocations
  x86/module: Use VM_GROUP_PAGES flag

 arch/x86/Kconfig         |   1 +
 arch/x86/kernel/module.c |   2 +-
 include/linux/list_lru.h |  13 +++
 include/linux/vmalloc.h  |   1 +
 mm/Kconfig               |   9 ++
 mm/list_lru.c            |  28 +++++
 mm/vmalloc.c             | 215 +++++++++++++++++++++++++++++++++++++--
 7 files changed, 257 insertions(+), 12 deletions(-)


             reply	other threads:[~2021-04-05 20:41 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-05 20:37 Rick Edgecombe [this message]
2021-04-05 20:37 ` [RFC 1/3] list: Support getting most recent element in list_lru Rick Edgecombe
2021-04-05 20:37 ` [RFC 2/3] vmalloc: Support grouped page allocations Rick Edgecombe
2021-04-05 21:01   ` Dave Hansen
2021-04-05 21:32     ` Matthew Wilcox
2021-04-05 21:49       ` Edgecombe, Rick P
2021-04-05 21:38     ` Edgecombe, Rick P
2021-04-05 20:37 ` [RFC 3/3] x86/module: Use VM_GROUP_PAGES flag Rick Edgecombe

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).