From: "Jason A. Donenfeld" <Jason@zx2c4.com>
To: Alexander Graf <graf@amazon.com>
Cc: Ard Biesheuvel <ardb@kernel.org>,
ACPI Devel Maling List <linux-acpi@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Len Brown <lenb@kernel.org>,
"Rafael J. Wysocki" <rafael@kernel.org>,
Greg KH <gregkh@linuxfoundation.org>,
"Woodhouse, David" <dwmw@amazon.co.uk>
Subject: Re: [PATCH] ACPI: bus: Match first 9 bytes of device IDs
Date: Fri, 25 Feb 2022 22:03:01 +0100 [thread overview]
Message-ID: <YhlEBUOeiP4jOIsf@zx2c4.com> (raw)
In-Reply-To: <a71a855f-9f3b-c99d-d4f9-c1ceb13c690d@amazon.com>
Hi Alex,
On Fri, Feb 25, 2022 at 08:06:39PM +0100, Alexander Graf wrote:
> On 25.02.22 19:39, Jason A. Donenfeld wrote:
> > Okay, the final piece, userspace:
> >
> > /sys/bus/acpi/devices/QEMUVGID:00/modalias gives:
> > acpi:QEMUVGID:VM_GEN_COUNTER:
> >
> > modinfo -F alias vmgenid.ko gives:
> > acpi*:VM_GEN_COUNTER:*
> >
> > udev src uses fnmatch.
> >
> > Bash confirms a match:
> >
> > $ [[ "acpi:QEMUVGID:VM_GEN_COUNTER:" == acpi*:VM_GEN_COUNTER:* ]] &&
> > echo matches
> > matches
> >
> > So I think with ACPI_ID_LEN --> 16 we are good to go.
>
>
> Is the size increase (mostly rodata I suppose? Anywhere else?) measurable?
On my test kernel, the size of vmlinux increases from 26918200 bytes to
26918200 bytes.
Wait, did I do that test right? I'll try again.
Yep, 26918200 -> 26918200, so it doesn't grow at all. I believe the
reason is mostly because of:
#define ACPI_ID_LEN 16
struct acpi_device_id {
__u8 id[ACPI_ID_LEN];
kernel_ulong_t driver_data;
__u32 cls;
__u32 cls_msk;
};
Because of the padding, 9->16 doesn't actually change the way this
structure is allocated. Then, additional uses of ACPI_ID_LEN throughout
the tree are rather sparse or enclosed within other structures or
similar things.
In other words, code size seems like very much a non-issue. Also, it's
not as though MIPS has ACPI. We're talking about x86, Itanium, and
(sometimes, I guess) arm64.
Regards,
Jason
prev parent reply other threads:[~2022-02-25 21:05 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-25 15:55 [PATCH] ACPI: bus: Match first 9 bytes of device IDs Alexander Graf
2022-02-25 16:57 ` Jason A. Donenfeld
2022-02-25 17:09 ` Alexander Graf
2022-02-25 17:16 ` Jason A. Donenfeld
2022-02-25 17:13 ` Ard Biesheuvel
2022-02-25 17:21 ` Jason A. Donenfeld
2022-02-25 17:30 ` Ard Biesheuvel
2022-02-25 17:33 ` Jason A. Donenfeld
2022-02-25 18:03 ` Jason A. Donenfeld
2022-02-25 18:39 ` Jason A. Donenfeld
2022-02-25 19:06 ` Alexander Graf
2022-02-25 21:03 ` Jason A. Donenfeld [this message]
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