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Re: [PATCH -tip 4/5] kprobes/x86: Use text_poke_smp_batch
- From: Masami Hiramatsu <mhiramat at redhat dot com>
- To: Mathieu Desnoyers <mathieu dot desnoyers at efficios dot com>
- Cc: Ingo Molnar <mingo at elte dot hu>, lkml <linux-kernel at vger dot kernel dot org>, systemtap <systemtap at sources dot redhat dot com>, DLE <dle-develop at lists dot sourceforge dot net>, Ananth N Mavinakayanahalli <ananth at in dot ibm dot com>, Jim Keniston <jkenisto at us dot ibm dot com>, Jason Baron <jbaron at redhat dot com>
- Date: Tue, 11 May 2010 20:41:54 -0400
- Subject: Re: [PATCH -tip 4/5] kprobes/x86: Use text_poke_smp_batch
- References: <20100510175313.27396.34605.stgit@localhost6.localdomain6> <20100510175340.27396.7222.stgit@localhost6.localdomain6> <20100511144013.GA17656@Krystal>
Mathieu Desnoyers wrote:
> * Masami Hiramatsu (mhiramat@redhat.com) wrote:
>> Use text_poke_smp_batch() in optimization path for reducing
>> the number of stop_machine() issues.
>>
>> Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
>> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
>> Cc: Ingo Molnar <mingo@elte.hu>
>> Cc: Jim Keniston <jkenisto@us.ibm.com>
>> Cc: Jason Baron <jbaron@redhat.com>
>> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
>> ---
>>
>> arch/x86/kernel/kprobes.c | 37 ++++++++++++++++++++++++++++++-------
>> include/linux/kprobes.h | 2 +-
>> kernel/kprobes.c | 13 +------------
>> 3 files changed, 32 insertions(+), 20 deletions(-)
>>
>> diff --git a/arch/x86/kernel/kprobes.c b/arch/x86/kernel/kprobes.c
>> index 345a4b1..63a5c24 100644
>> --- a/arch/x86/kernel/kprobes.c
>> +++ b/arch/x86/kernel/kprobes.c
>> @@ -1385,10 +1385,14 @@ int __kprobes arch_prepare_optimized_kprobe(struct optimized_kprobe *op)
>> return 0;
>> }
>>
>> -/* Replace a breakpoint (int3) with a relative jump. */
>> -int __kprobes arch_optimize_kprobe(struct optimized_kprobe *op)
>> +#define MAX_OPTIMIZE_PROBES 256
>
> So what kind of interrupt latency does a 256-probes batch generate on the
> system ? Are we talking about a few milliseconds, a few seconds ?
>From my experiment on kvm/4cpu, it took about 3 seconds in average.
With this patch, it went down to 30ms. (x100 faster :))
Thank you,
--
Masami Hiramatsu
e-mail: mhiramat@redhat.com