From: Daniel Walker <danielwa@cisco.com>
To: David Woodhouse <dwmw2@infradead.org>
Cc: "Nikunj Kela (nkela)" <nkela@cisco.com>,
Richard Weinberger <richard.weinberger@gmail.com>,
"linux-mtd @ lists . infradead . org"
<linux-mtd@lists.infradead.org>,
LKML <linux-kernel@vger.kernel.org>,
"xe-linux-external(mailer list)" <xe-linux-external@cisco.com>
Subject: Re: [PATCH] jffs2: implement mount option to configure endianness
Date: Mon, 12 Nov 2018 14:50:15 -0800 [thread overview]
Message-ID: <20181112225015.jyuro3z3ygavnvrp@zorba> (raw)
In-Reply-To: <20181112214333.lplffcc722hta43v@zorba>
On Mon, Nov 12, 2018 at 01:43:33PM -0800, Daniel Walker wrote:
> On Thu, Nov 08, 2018 at 07:47:08PM +0000, David Woodhouse wrote:
> > On Thu, 2018-11-08 at 18:01 +0000, Nikunj Kela (nkela) wrote:
> > > But we can hypothesise and handwave about it until the cows come home;
> > > I'd like to see a real test of whether it actually makes a difference
> > > that we care about.
> > >
> > > If it does, one option might be to just build separate versions of
> > > scan.c for each endianness, since that's the critical path we care
> > > about.
> > >
> > > I wonder if this feature is really that important that we need to duplicate the drivers.
> > > Also, it might take some time for me to find some device that I can run the tests with and without this patch.
> >
> > Hm?
> >
> > # modprobe mtdram size=16384
> > # mount -tjffs2 mtd0 /mnt
> > # cp -av .git /mnt # until it fills up
> > # umount /mnt
> > # perf record mount -tjffs2 mtd0 /mnt
> >
> > On my desktop 'perf' only gets about 12 samples from that, so it's not
> > ideal. But you can make the mtdram device bigger, use something other
> > than my shiny new laptop, and use a higher sample frequency from 'perf'
> > and you should be able to get some vaguely meaningful results.
> >
>
Made a little mistake. The first tests were with Nikunj's very first version
which was just a pure Kconfig option. I reran the test of the second version and
increased the mtdram space to 100megs.
baseline below,
sh-4.2# perf stat -B mount -t jffs2 /dev/mtdblock7 /mnt
jffs2: Flash size not aligned to erasesize, reducing to 99944KiB
Performance counter stats for 'mount -t jffs2 /dev/mtdblock7 /mnt':
100.303072 task-clock # 0.775 CPUs utilized
19 context-switches # 0.189 K/sec
0 cpu-migrations # 0.000 K/sec
94 page-faults # 0.937 K/sec
134135872 cycles # 1.337 GHz [92.88%]
29217497 stalled-cycles-frontend # 21.78% frontend cycles idle [92.02%]
10493221 stalled-cycles-backend # 7.82% backend cycles idle [92.05%]
136740541 instructions # 1.02 insns per cycle
# 0.21 stalled cycles per insn [92.04%]
14639149 branches # 145.949 M/sec [19.06%]
1384856 branch-misses # 9.46% of all branches [16.29%]
0.129377322 seconds time elapsed
This is with the mount option changes added.
sh-4.2# perf stat -B mount -t jffs2 /dev/mtdblock7 /mnt
jffs2: Flash size not aligned to erasesize, reducing to 99944KiB
Performance counter stats for 'mount -t jffs2 /dev/mtdblock7 /mnt':
100.516160 task-clock # 0.315 CPUs utilized
14 context-switches # 0.139 K/sec
0 cpu-migrations # 0.000 K/sec
94 page-faults # 0.935 K/sec
129255757 cycles # 1.286 GHz [19.32%]
26930446 stalled-cycles-frontend # 20.84% frontend cycles idle [92.00%]
10068627 stalled-cycles-backend # 7.79% backend cycles idle [92.05%]
138000320 instructions # 1.07 insns per cycle
# 0.20 stalled cycles per insn [92.04%]
26158985 branches # 260.247 M/sec [90.09%]
1242606 branch-misses # 4.75% of all branches [19.24%]
0.319593555 seconds time elapsed
It looks like the took slightly more than twice as long to mount.
Daniel
next prev parent reply other threads:[~2018-11-12 22:50 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-06 21:49 [PATCH] jffs2: implement mount option to configure endianness Nikunj Kela
2018-11-07 9:05 ` David Woodhouse
2018-11-07 9:16 ` Joakim Tjernlund
2018-11-07 16:12 ` David Woodhouse
2018-11-07 17:33 ` Daniel Walker
2018-11-07 17:58 ` David Woodhouse
2018-11-07 18:41 ` Joakim Tjernlund
2018-11-08 15:25 ` Christoph Hellwig
2018-11-07 19:21 ` Daniel Walker
2018-11-07 18:04 ` Nikunj Kela (nkela)
2018-11-07 18:14 ` Richard Weinberger
2018-11-08 8:11 ` David Woodhouse
2018-11-08 18:01 ` Nikunj Kela (nkela)
2018-11-08 18:50 ` Joakim Tjernlund
2018-11-08 19:47 ` David Woodhouse
2018-11-12 21:43 ` Daniel Walker
2018-11-12 22:50 ` Daniel Walker [this message]
2018-11-12 23:11 ` David Woodhouse
2018-11-12 23:40 ` Daniel Walker
2018-11-12 23:43 ` David Woodhouse
2018-11-13 0:06 ` Daniel Walker
2018-11-13 21:01 ` Daniel Walker
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:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20181112225015.jyuro3z3ygavnvrp@zorba \
--to=danielwa@cisco.com \
--cc=dwmw2@infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mtd@lists.infradead.org \
--cc=nkela@cisco.com \
--cc=richard.weinberger@gmail.com \
--cc=xe-linux-external@cisco.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* 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).