linux-kernel - Re: [PATCH -tip v7 24/26] kprobes: Enlarge hash table to 4096 entries

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Message-ID: <87y50wut4j.fsf@tassilo.jf.intel.com>
Date:	Thu, 27 Feb 2014 13:45:48 -0800
From:	Andi Kleen <andi@...stfloor.org>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Sandeepa Prabhu <sandeepa.prabhu@...aro.org>,
	Frederic Weisbecker <fweisbec@...il.com>, x86@...nel.org,
	Steven Rostedt <rostedt@...dmis.org>, fche@...hat.com,
	mingo@...hat.com, systemtap@...rceware.org,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH -tip v7 24/26] kprobes: Enlarge hash table to 4096 entries

Masami Hiramatsu <masami.hiramatsu.pt@...achi.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) 

And then if you enlarge the table please allocate
it dynamically on the first use.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only
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