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Re: [PATCH -tip v7 24/26] kprobes: Enlarge hash table to 4096 entries
- From: Masami Hiramatsu <masami dot hiramatsu dot pt at hitachi dot com>
- To: Andi Kleen <andi at firstfloor dot org>
- Cc: linux-kernel at vger dot kernel dot org, Ingo Molnar <mingo at kernel dot org>, Ananth N Mavinakayanahalli <ananth at in dot ibm dot com>, Sandeepa Prabhu <sandeepa dot prabhu at linaro dot org>, Frederic Weisbecker <fweisbec at gmail dot com>, x86 at kernel dot org, Steven Rostedt <rostedt at goodmis dot org>, fche at redhat dot com, mingo at redhat dot com, systemtap at sourceware dot org, "H. Peter Anvin" <hpa at zytor dot com>, Thomas Gleixner <tglx at linutronix dot de>
- Date: Fri, 28 Feb 2014 07:22:17 +0900
- Subject: Re: [PATCH -tip v7 24/26] kprobes: Enlarge hash table to 4096 entries
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- References: <20140227073315 dot 20992 dot 6174 dot stgit at ltc230 dot yrl dot intra dot hitachi dot co dot jp> <20140227073414 dot 20992 dot 16882 dot stgit at ltc230 dot yrl dot intra dot hitachi dot co dot jp> <87y50wut4j dot fsf at tassilo dot jf dot intel dot com>
(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.
> And then if you enlarge the table please allocate
> it dynamically on the first use.
OK, I'll try to do so.
Thank you,
--
Masami HIRAMATSU
IT Management Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com