linux-kernel - Re: [RFC PATCH tip 0/5] tracing filters with BPF

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Message-ID: <CAMEtUuzQXo2kwoBUxq0PKOWA=T4WXtg3Bj8vzYvQquzW+isMSA@mail.gmail.com>
Date:	Thu, 5 Dec 2013 11:43:13 -0800
From:	Alexei Starovoitov <ast@...mgrid.com>
To:	"Frank Ch. Eigler" <fche@...hat.com>
Cc:	Andi Kleen <andi@...stfloor.org>, Ingo Molnar <mingo@...nel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Tom Zanussi <tom.zanussi@...ux.intel.com>,
	Jovi Zhangwei <jovi.zhangwei@...il.com>,
	Eric Dumazet <edumazet@...gle.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH tip 0/5] tracing filters with BPF

On Thu, Dec 5, 2013 at 8:11 AM, Frank Ch. Eigler <fche@...hat.com> wrote:
>
> ast wrote:
>
>>>[...]
>> Did simple ktap test with 1M alloc_skb/kfree_skb toy test from earlier email:
>> trace skb:kfree_skb {
>>         if (arg2 == 0x100) {
>>                 printf("%x %x\n", arg1, arg2)
>>         }
>> }
>> [...]
>
> For reference, you might try putting systemtap into the performance
> comparison matrix too:
>
> # stap -e 'probe kernel.trace("kfree_skb") {
>               if ($location == 0x100 /* || $location == 0x200 etc. */ ) {
>                  printf("%x %x\n", $skb, $location)
>               }
>            }'

stap with one 'if': 1M skb alloc/free 200696 (usecs)
stap with 10 'if': 1M skb alloc/free 202135 (usecs)

so systemtap entry overhead is a bit higher than bpf and extra if-s
show the same progression as expected.
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