From: "George Spelvin" <linux@horizon.com>
To: linux@horizon.com, tytso@mit.edu
Cc: hpa@linux.intel.com, linux-kernel@vger.kernel.org,
mingo@kernel.org, price@mit.edu
Subject: Re: [RFC PATCH] drivers/char/random.c: Is reducing locking range like this safe?
Date: 9 Jun 2014 00:03:55 -0400 [thread overview]
Message-ID: <20140609040355.8126.qmail@ns.horizon.com> (raw)
In-Reply-To: <20140609021820.2038.qmail@ns.horizon.com>
Sigh, adventures in "unable to mount root filesystem" currently underway.
Tested on a different computer without patches (half size, since it's
an older machine):
Writing 16 MiB:
16777216 bytes (17 MB) copied, 0.289169 s, 58.0 MB/s
16777216 bytes (17 MB) copied, 0.289378 s, 58.0 MB/s
Writing while reading:
16777216 bytes (17 MB) copied, 0.538839 s, 31.1 MB/s
4194304 bytes (4.2 MB) copied, 0.544769 s, 7.7 MB/s
16777216 bytes (17 MB) copied, 0.537425 s, 31.2 MB/s
4194304 bytes (4.2 MB) copied, 0.544259 s, 7.7 MB/s
16777216 bytes (17 MB) copied, 0.740495 s, 22.7 MB/s
4194304 bytes (4.2 MB) copied, 0.879353 s, 4.8 MB/s
4194304 bytes (4.2 MB) copied, 0.879629 s, 4.8 MB/s
16777216 bytes (17 MB) copied, 0.7262 s, 23.1 MB/s
4194304 bytes (4.2 MB) copied, 0.877035 s, 4.8 MB/s
4194304 bytes (4.2 MB) copied, 0.880627 s, 4.8 MB/s
16777216 bytes (17 MB) copied, 0.996933 s, 16.8 MB/s
4194304 bytes (4.2 MB) copied, 1.24551 s, 3.4 MB/s
4194304 bytes (4.2 MB) copied, 1.26138 s, 3.3 MB/s
4194304 bytes (4.2 MB) copied, 1.2664 s, 3.3 MB/s
16777216 bytes (17 MB) copied, 0.969144 s, 17.3 MB/s
4194304 bytes (4.2 MB) copied, 1.25311 s, 3.3 MB/s
4194304 bytes (4.2 MB) copied, 1.26076 s, 3.3 MB/s
4194304 bytes (4.2 MB) copied, 1.25887 s, 3.3 MB/s
Summarized:
0 readers: 0.289169 0.289378
1 reader: 0.538839 0.537425 (+86%)
2 readers: 0.740495 0.726200 (+153%)
3 readers: 0.996933 0.969144 (+240%)
That seems... noticeable. Causing iterrupt latency problems is defintiely
a theoretical extrapolation, however.
For comparison, on this system, dd from /dev/zero runs at 1 GB/s per
thread for up to 4 threads with no interference.
*Really* confusingly, dd from /dev/zero to tmpfs runs at 450 MB/s (per
thread) for 2 to 4 threads, but 325 MB/s for 1 thread. NFclue.
(This is writing to separate files; writing the the same file is
slower.)
dd from tmpfs to tmpfs runs at about 380 MB/s, again independent
of the number of threads up to the number of CPUs.
next prev parent reply other threads:[~2014-06-09 4:04 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-09 0:05 George Spelvin
2014-06-09 1:35 ` Theodore Ts'o
2014-06-09 2:10 ` George Spelvin
2014-06-09 2:18 ` George Spelvin
2014-06-09 4:03 ` George Spelvin [this message]
2014-06-09 9:23 ` George Spelvin
2014-06-09 13:34 ` Theodore Ts'o
2014-06-09 15:04 ` George Spelvin
2014-06-09 15:50 ` Theodore Ts'o
2014-06-09 16:11 ` George Spelvin
2014-06-10 0:20 ` drivers/char/random.c: more ruminations George Spelvin
2014-06-10 1:20 ` Theodore Ts'o
2014-06-10 3:10 ` George Spelvin
2014-06-10 15:25 ` Theodore Ts'o
2014-06-10 20:40 ` George Spelvin
2014-06-10 21:20 ` Theodore Ts'o
2014-06-11 0:10 ` George Spelvin
2014-06-11 2:08 ` Theodore Ts'o
2014-06-11 3:58 ` George Spelvin
2014-06-11 13:11 ` Theodore Ts'o
2014-06-12 0:42 ` George Spelvin
2014-06-12 1:03 ` H. Peter Anvin
2014-06-11 4:34 ` George Spelvin
2014-06-11 13:09 ` Theodore Ts'o
2014-06-11 2:21 ` Theodore Ts'o
2014-06-09 13:17 ` drivers/char/random.c: More futzing about George Spelvin
2014-06-11 16:38 ` Theodore Ts'o
2014-06-11 16:48 ` H. Peter Anvin
2014-06-11 19:25 ` Theodore Ts'o
2014-06-11 20:41 ` H. Peter Anvin
2014-06-12 0:44 ` H. Peter Anvin
2014-06-12 1:51 ` George Spelvin
2014-06-12 0:32 ` George Spelvin
2014-06-12 3:22 ` Theodore Ts'o
2014-06-12 4:13 ` random: Benchamrking fast_mix2 George Spelvin
2014-06-12 11:18 ` George Spelvin
2014-06-12 20:17 ` Theodore Ts'o
2014-06-12 20:46 ` Theodore Ts'o
2014-06-13 0:23 ` George Spelvin
2014-06-13 15:52 ` Theodore Ts'o
2014-06-14 2:10 ` George Spelvin
2014-06-14 3:06 ` Theodore Ts'o
2014-06-14 5:25 ` George Spelvin
2014-06-14 6:24 ` Theodore Ts'o
2014-06-14 8:03 ` George Spelvin
2014-06-14 11:14 ` George Spelvin
2014-06-14 15:13 ` George Spelvin
2014-06-14 16:33 ` Theodore Ts'o
2014-06-15 0:23 ` George Spelvin
2014-06-15 1:17 ` Theodore Ts'o
2014-06-15 6:58 ` George Spelvin
2014-06-15 13:01 ` Theodore Ts'o
2014-06-14 6:27 ` Theodore Ts'o
2014-06-14 4:55 ` [RFC] random: is the IRQF_TIMER test working as intended? George Spelvin
2014-06-14 6:43 ` Theodore Ts'o
2014-06-14 7:23 ` George Spelvin
2014-06-12 3:43 ` drivers/char/random.c: More futzing about George Spelvin
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=20140609040355.8126.qmail@ns.horizon.com \
--to=linux@horizon.com \
--cc=hpa@linux.intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=price@mit.edu \
--cc=tytso@mit.edu \
/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
Powered by JetHome