From: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
To: Andi Kleen <andi@firstfloor.org>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@kernel.org>,
Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
Sandeepa Prabhu <sandeepa.prabhu@linaro.org>,
Frederic Weisbecker <fweisbec@gmail.com>,
x86@kernel.org, Steven Rostedt <rostedt@goodmis.org>,
fche@redhat.com, mingo@redhat.com, systemtap@sourceware.org,
"H. Peter Anvin" <hpa@zytor.com>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: Re: [PATCH -tip v7 24/26] kprobes: Enlarge hash table to 4096 entries
Date: Mon, 03 Mar 2014 09:31:00 -0000 [thread overview]
Message-ID: <53144C01.60106@hitachi.com> (raw)
In-Reply-To: <530FBA99.3050504@hitachi.com>
(2014/02/28 7:22), Masami Hiramatsu wrote:
> (2014/02/28 6:45), Andi Kleen wrote:
>> Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> writes:
>>
>>> Currently, since the kprobes expects to be used
>>> with less than 100 probe points, its hash table
>>> just has 64 entries. This is too little to handle
>>> several thousands of probes.
>>> Enlarge this to 4096 entires which just consumes
>>> 32KB (on 64bit arch) for better scalability.
>>
>> 32K for a debug feature that most systems never use seems
>> too large to me.
>>
>> First can you check if smaller hash tables work too
>> (perhaps with a better hash, like jhash)
>
> I doubt jhash helps it, but yes, at least the various size
> should be tested.
Here, I tested the hash table performance with 2^6 to 2^12.
Cycles% of get_kprobe with 10k probes:
Size Cycles%
2^6 95.58%
2^7 85.83%
2^8 68.43%
2^9 48.61%
2^10 46.95%
2^11 48.46%
2^12 56.95%
So, we can see the hash table larger than 2^9 (512 entries,
which consumes 4KB) has no performance improvement.
Would you think 4kB is still big for kprobes? :)
Thank you,
--
Masami HIRAMATSU
IT Management Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com
next prev parent reply other threads:[~2014-03-03 9:31 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-27 7:33 [PATCH -tip v7 00/26] kprobes: introduce NOKPROBE_SYMBOL, bugfixes and scalbility efforts Masami Hiramatsu
2014-02-27 7:33 ` [PATCH -tip v7 12/26] ftrace/*probes: Allow probing on some functions Masami Hiramatsu
2014-02-27 7:33 ` [PATCH -tip v7 01/26] [BUGFIX]kprobes/x86: Fix page-fault handling logic Masami Hiramatsu
2014-02-27 7:33 ` [PATCH -tip v7 10/26] kprobes/x86: Allow probe on some kprobe preparation functions Masami Hiramatsu
2014-02-27 7:33 ` [PATCH -tip v7 07/26] [BUGFIX] x86: Prohibit probing on thunk functions and restore Masami Hiramatsu
2014-02-27 7:33 ` [PATCH -tip v7 03/26] kprobes: Prohibit probing on .entry.text code Masami Hiramatsu
2014-02-27 7:33 ` [PATCH -tip v7 06/26] [BUGFIX] x86: Prohibit probing on native_set_debugreg/load_idt Masami Hiramatsu
2014-02-27 7:33 ` [PATCH -tip v7 09/26] x86: Call exception_enter after kprobes handled Masami Hiramatsu
2014-02-27 7:33 ` [PATCH -tip v7 11/26] kprobes: Allow probe on some kprobe functions Masami Hiramatsu
2014-02-27 7:33 ` [PATCH -tip v7 13/26] x86: Allow kprobes on text_poke/hw_breakpoint Masami Hiramatsu
2014-02-27 7:33 ` [PATCH -tip v7 04/26] kprobes: Introduce NOKPROBE_SYMBOL() macro for blacklist Masami Hiramatsu
2014-02-27 7:33 ` [PATCH -tip v7 08/26] kprobes/x86: Call exception handlers directly from do_int3/do_debug Masami Hiramatsu
2014-02-27 7:33 ` [PATCH -tip v7 15/26] kprobes: Use NOKPROBE_SYMBOL macro instead of __kprobes Masami Hiramatsu
2014-02-27 7:33 ` [PATCH -tip v7 02/26] kprobes/x86: Allow to handle reentered kprobe on singlestepping Masami Hiramatsu
2014-02-27 7:33 ` [PATCH -tip v7 05/26] [BUGFIX] kprobes/x86: Prohibit probing on debug_stack_* Masami Hiramatsu
2014-02-27 7:34 ` [PATCH -tip v7 25/26] kprobes: Introduce kprobe cache to reduce cache misshits Masami Hiramatsu
2014-02-27 7:34 ` [PATCH -tip v7 20/26] kprobes: Support blacklist functions in module Masami Hiramatsu
2014-02-27 7:34 ` [PATCH -tip v7 24/26] kprobes: Enlarge hash table to 4096 entries Masami Hiramatsu
2014-02-27 21:46 ` Andi Kleen
2014-02-27 22:22 ` Masami Hiramatsu
2014-03-03 9:31 ` Masami Hiramatsu [this message]
2014-03-03 17:20 ` Andi Kleen
2014-03-04 1:54 ` Masami Hiramatsu
2014-02-27 7:34 ` [PATCH -tip v7 17/26] notifier: Use NOKPROBE_SYMBOL macro in notifier Masami Hiramatsu
2014-02-27 7:34 ` [PATCH -tip v7 19/26] kprobes: Show blacklist entries via debugfs Masami Hiramatsu
2014-02-27 7:34 ` [PATCH -tip v7 16/26] ftrace/kprobes: Use NOKPROBE_SYMBOL macro in ftrace Masami Hiramatsu
2014-02-27 7:34 ` [PATCH -tip v7 18/26] sched: Use NOKPROBE_SYMBOL macro in sched Masami Hiramatsu
2014-02-27 7:34 ` [PATCH -tip v7 21/26] kprobes: Use NOKPROBE_SYMBOL() in sample modules Masami Hiramatsu
2014-02-27 7:34 ` [PATCH -tip v7 23/26] kprobes/x86: Remove unneeded preempt_disable/enable in interrupt handlers Masami Hiramatsu
2014-02-27 7:34 ` [PATCH -tip v7 26/26] ftrace: Introduce FTRACE_OPS_FL_SELF_FILTER for ftrace-kprobe Masami Hiramatsu
2014-02-27 7:34 ` [PATCH -tip v7 14/26] x86: Use NOKPROBE_SYMBOL() instead of __kprobes annotation Masami Hiramatsu
2014-02-27 7:34 ` [PATCH -tip v7 22/26] kprobes/x86: Use kprobe_blacklist for .kprobes.text and .entry.text Masami Hiramatsu
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=53144C01.60106@hitachi.com \
--to=masami.hiramatsu.pt@hitachi.com \
--cc=ananth@in.ibm.com \
--cc=andi@firstfloor.org \
--cc=fche@redhat.com \
--cc=fweisbec@gmail.com \
--cc=hpa@zytor.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=mingo@redhat.com \
--cc=rostedt@goodmis.org \
--cc=sandeepa.prabhu@linaro.org \
--cc=systemtap@sourceware.org \
--cc=tglx@linutronix.de \
--cc=x86@kernel.org \
/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 read-only IMAP folder(s) and NNTP newsgroup(s).