From: Song Liu <firstname.lastname@example.org>
To: Christoph Hellwig <email@example.com>,
Claudio Imbrenda <firstname.lastname@example.org>,
Nicholas Piggin <email@example.com>
Cc: "firstname.lastname@example.org" <email@example.com>,
Song Liu <firstname.lastname@example.org>,
Linux Memory Management List <email@example.com>,
bpf <firstname.lastname@example.org>, Networking <email@example.com>,
X86 ML <firstname.lastname@example.org>, Alexei Starovoitov <email@example.com>,
Daniel Borkmann <firstname.lastname@example.org>,
Kernel Team <Kernelemail@example.com>,
Subject: Re: [PATCH bpf 0/4] introduce HAVE_ARCH_HUGE_VMALLOC_FLAG for bpf_prog_pack
Date: Thu, 7 Apr 2022 19:57:25 +0000 [thread overview]
Message-ID: <16491AB0-7FFD-40F5-A331-65B68F548A3B@fb.com> (raw)
Hi Nicholas and Claudio,
> On Apr 5, 2022, at 4:54 PM, Song Liu <firstname.lastname@example.org> wrote:
>> On Apr 5, 2022, at 12:07 AM, Christoph Hellwig <email@example.com> wrote:
>> On Fri, Apr 01, 2022 at 10:22:00PM +0000, Song Liu wrote:
>>>>> Please fix the underlying issues instead of papering over them and
>>>>> creating a huge maintainance burden for others.
>>> After reading the code a little more, I wonder what would be best strategy.
>>> IIUC, most of the kernel is not ready for huge page backed vmalloc memory.
>>> For example, all the module_alloc cannot work with huge pages at the moment.
>>> And the error Paul Menzel reported in drm_fb_helper.c will probably hit
>>> powerpc with 5.17 kernel as-is? (trace attached below)
>>> Right now, we have VM_NO_HUGE_VMAP to let a user to opt out of huge pages.
>>> However, given there are so many users of vmalloc, vzalloc, etc., we
>>> probably do need a flag for the user to opt-in?
>>> Does this make sense? Any recommendations are really appreciated.
>> I think there is multiple aspects here:
>> - if we think that the kernel is not ready for hugepage backed vmalloc
>> in general we need to disable it in powerpc for now.
> Nicholas and Claudio,
> What do you think about the status of hugepage backed vmalloc on powerpc?
> I found module_alloc and kvm_s390_pv_alloc_vm() opt-out of huge pages.
> But I am not aware of users that benefit from huge pages (except vfs hash,
> which was mentioned in 8abddd968a30). Does an opt-in flag (instead of
> current opt-out flag, VM_NO_HUGE_VMAP) make sense to you?
Could you please share your comments on this? Specifically, does it make
sense to replace VM_NO_HUGE_VMAP with an opt-in flag? If we think current
opt-out flag is better approach, what would be the best practice to find
all the cases to opt-out?
>> - if we think even in the longer run only some users can cope with
>> hugepage backed vmalloc we need to turn it into an opt-in in
>> general and not just for x86
>> - there still to appear various unresolved underlying x86 specific
>> issues that need to be fixed either way
next prev parent reply other threads:[~2022-04-07 20:32 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <firstname.lastname@example.org>
[not found] ` <email@example.com>
2022-03-30 23:40 ` [PATCH bpf 2/4] vmalloc: introduce HAVE_ARCH_HUGE_VMALLOC_FLAG Edgecombe, Rick P
2022-03-31 0:26 ` Song Liu
[not found] ` <firstname.lastname@example.org>
2022-03-30 23:47 ` [PATCH bpf 1/4] x86: disable HAVE_ARCH_HUGE_VMALLOC Thomas Gleixner
[not found] ` <email@example.com>
2022-03-30 23:54 ` [PATCH bpf 3/4] x86: select HAVE_ARCH_HUGE_VMALLOC_FLAG for X86_64 Thomas Gleixner
2022-03-31 0:30 ` Song Liu
[not found] ` <firstname.lastname@example.org>
2022-03-31 0:00 ` [PATCH bpf 4/4] bpf: use __vmalloc_node_range() with VM_TRY_HUGE_VMAP for bpf_prog_pack Thomas Gleixner
2022-03-31 0:31 ` Song Liu
2022-03-31 0:04 ` [PATCH bpf 0/4] introduce HAVE_ARCH_HUGE_VMALLOC_FLAG " Edgecombe, Rick P
2022-03-31 0:46 ` Song Liu
2022-03-31 16:19 ` Edgecombe, Rick P
2022-03-31 5:37 ` Christoph Hellwig
2022-03-31 23:59 ` Song Liu
2022-04-01 22:22 ` Song Liu
2022-04-05 7:07 ` Christoph Hellwig
2022-04-05 23:54 ` Song Liu
2022-04-07 19:57 ` Song Liu [this message]
2022-04-08 10:08 ` Claudio Imbrenda
2022-04-08 21:22 ` Song Liu
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).