From: David Hildenbrand <david@redhat.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luis Chamberlain <mcgrof@kernel.org>,
Johan Hovold <johan@kernel.org>,
Lucas De Marchi <lucas.demarchi@intel.com>,
Petr Pavlu <petr.pavlu@suse.com>,
gregkh@linuxfoundation.org, rafael@kernel.org, song@kernel.org,
lucas.de.marchi@gmail.com, christophe.leroy@csgroup.eu,
peterz@infradead.org, rppt@kernel.org, dave@stgolabs.net,
willy@infradead.org, vbabka@suse.cz, mhocko@suse.com,
dave.hansen@linux.intel.com, colin.i.king@gmail.com,
jim.cromie@gmail.com, catalin.marinas@arm.com, jbaron@akamai.com,
rick.p.edgecombe@intel.com, yujie.liu@intel.com,
tglx@linutronix.de, hch@lst.de, patches@lists.linux.dev,
linux-modules@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, pmladek@suse.com,
prarit@redhat.com, lennart@poettering.net
Subject: Re: [PATCH 2/2] module: add support to avoid duplicates early on load
Date: Fri, 2 Jun 2023 18:37:09 +0200 [thread overview]
Message-ID: <6711d7ba-1349-de28-6d35-9dce91be7996@redhat.com> (raw)
In-Reply-To: <CAHk-=whwFoC30zoTfsQAvkDRvgMCovwKGW_R1PPnqiF+YemcOA@mail.gmail.com>
On 02.06.23 18:06, Linus Torvalds wrote:
> On Fri, Jun 2, 2023 at 11:20 AM David Hildenbrand <david@redhat.com> wrote:
>>
>> What concerns me a bit, is that on the patched kernel we seem to hit more cases where
>> boot takes much longer (in both kernel configs).
>
> So it potentially serializes the loads to the same file more, but in
> the process uses much less memory (since the ones waiting will not
> have done any of the "load file contents and uncompress them"). So
> it's a bit of a trade-off.
I have the feeling that -- on this system -- it's some inaccurate
accounting of firmware+loader times to the kernel startup time. Combined
with some other noise. Especially the firmware loading time seems to be
fairly randomized.
I guess what we care about regarding module loading is the
initrd+userspace loading times, and they are fairly stable. But we
mostly care about udev.
So let's look only at "systemd-udev" services:
1) !debug
a) master
5.672s systemd-udev-settle.service
505ms systemd-udev-trigger.service
272ms systemd-udevd.service
5.418s systemd-udev-settle.service
487ms systemd-udev-trigger.service
258ms systemd-udevd.service
5.707s systemd-udev-settle.service
527ms systemd-udev-trigger.service
273ms systemd-udevd.service
6.250s systemd-udev-settle.service
455ms systemd-udev-trigger.service
283ms systemd-udevd.service
b) patched
4.652s systemd-udev-settle.service
461ms systemd-udev-trigger.service
302ms systemd-udevd.service
4.652s systemd-udev-settle.service
461ms systemd-udev-trigger.service
302ms systemd-udevd.service
4.634s systemd-udev-settle.service
444ms systemd-udev-trigger.service
296ms systemd-udevd.service
4.745s systemd-udev-settle.service
444ms systemd-udev-trigger.service
273ms systemd-udevd.service
2) debug
a) master
32.806s systemd-udev-settle.service
9.584s systemd-udev-trigger.service
471ms systemd-udevd.service
29.901s systemd-udev-settle.service
8.914s systemd-udev-trigger.service
400ms systemd-udevd.service
28.640s systemd-udev-settle.service
9.260s systemd-udev-trigger.service
477ms systemd-udevd.service
29.498s systemd-udev-settle.service
9.073s systemd-udev-trigger.service
444ms systemd-udevd.service
b) patched
28.765s systemd-udev-settle.service
8.898s systemd-udev-trigger.service
400ms systemd-udevd.service
28.292s systemd-udev-settle.service
8.903s systemd-udev-trigger.service
401ms systemd-udevd.service
34.588s systemd-udev-settle.service
8.959s systemd-udev-trigger.service
455ms systemd-udevd.service
28.641s systemd-udev-settle.service
8.953s systemd-udev-trigger.service
389ms systemd-udevd.service
So except some noise, in the general case the patched version seems to
be faster just looking at systemd-udev.
>
> We could complicate things a bit, and let other callers return -EEXIST
> a bit earlier, but I'm not convinced it really matters.
Looking at the numbers, agreed.
>
> Honestly, taking too long because user space does something stupid and
> wrong is not a kernel bug. Not booting because we use too much memory
> - that's problematic. But booting slowly because udev does several
> thousand unnecessary module loads is entirely on udev.
Yes.
I'll do some more experiments, but from what I can tell
Tested-by: David Hildenbrand <david@redhat.com>
--
Cheers,
David / dhildenb
next prev parent reply other threads:[~2023-06-02 16:37 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-24 21:36 [PATCH 0/2] module: avoid all memory pressure due to duplicates Luis Chamberlain
2023-05-24 21:36 ` [PATCH 1/2] fs/kernel_read_file: add support for duplicate detection Luis Chamberlain
2023-05-24 21:52 ` Linus Torvalds
2023-05-24 21:56 ` Linus Torvalds
2023-05-24 22:07 ` Luis Chamberlain
2023-05-25 4:00 ` Linus Torvalds
2023-05-25 18:08 ` Luis Chamberlain
2023-05-25 18:35 ` Luis Chamberlain
2023-05-25 18:50 ` Linus Torvalds
2023-05-25 19:32 ` Luis Chamberlain
2023-05-25 7:01 ` Christian Brauner
2023-05-24 21:36 ` [PATCH 2/2] module: add support to avoid duplicates early on load Luis Chamberlain
2023-05-25 11:40 ` Petr Pavlu
2023-05-25 16:07 ` Linus Torvalds
2023-05-25 16:42 ` Greg KH
2023-05-25 18:22 ` Luis Chamberlain
2023-05-25 17:52 ` Linus Torvalds
2023-05-25 18:45 ` Lucas De Marchi
2023-05-25 21:12 ` Linus Torvalds
2023-05-25 22:02 ` Luis Chamberlain
2023-05-26 1:39 ` Linus Torvalds
2023-05-29 8:58 ` Johan Hovold
2023-05-29 11:00 ` Linus Torvalds
2023-05-29 12:44 ` Johan Hovold
2023-05-29 15:18 ` Johan Hovold
2023-05-30 1:55 ` Linus Torvalds
2023-05-30 9:40 ` Johan Hovold
2023-06-05 12:25 ` Johan Hovold
2023-05-30 16:22 ` Luis Chamberlain
2023-05-30 17:16 ` Lucas De Marchi
2023-05-30 19:41 ` Luis Chamberlain
2023-05-30 22:17 ` Linus Torvalds
2023-05-31 5:30 ` Lucas De Marchi
2023-05-31 0:31 ` Luis Chamberlain
2023-05-31 7:51 ` David Hildenbrand
2023-05-31 16:57 ` Luis Chamberlain
2023-06-02 15:19 ` David Hildenbrand
2023-06-02 16:04 ` Luis Chamberlain
2023-06-05 11:26 ` David Hildenbrand
2023-06-05 15:17 ` Luis Chamberlain
2023-06-05 15:28 ` Luis Chamberlain
2023-06-28 18:52 ` Luis Chamberlain
2023-06-28 20:14 ` Linus Torvalds
2023-06-28 22:07 ` Linus Torvalds
2023-06-28 23:17 ` Linus Torvalds
2023-06-29 0:18 ` Luis Chamberlain
2023-06-02 16:06 ` Linus Torvalds
2023-06-02 16:37 ` David Hildenbrand [this message]
2023-05-30 22:45 ` Dan Williams
2023-06-04 14:26 ` Rudi Heitbaum
2023-05-29 17:47 ` Linus Torvalds
2023-05-30 10:01 ` Johan Hovold
2023-05-25 16:54 ` Lucas De Marchi
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