From: Lee Revell <rlrevell@joe-job.com>
To: Dave Jones <davej@redhat.com>
Cc: Jan Engelhardt <jengelh@linux01.gwdg.de>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] no need to check for NULL before calling kfree() -fs/ext2/
Date: Mon, 28 Mar 2005 21:52:57 -0500 [thread overview]
Message-ID: <1112064777.19014.17.camel@mindpipe> (raw)
In-Reply-To: <20050327174026.GA708@redhat.com>
On Sun, 2005-03-27 at 12:40 -0500, Dave Jones wrote:
> On Sun, Mar 27, 2005 at 05:12:58PM +0200, Jan Engelhardt wrote:
>
> > Well, kfree inlined was already mentioned but forgotten again.
> > What if this was used:
> >
> > inline static void kfree_WRAP(void *addr) {
> > if(likely(addr != NULL)) {
> > kfree_real(addr);
> > }
> > return;
> > }
> >
> > And remove the NULL-test in kfree_real()? Then we would have:
>
> Am I the only person who is completely fascinated by the
> effort being spent here micro-optimising something thats
> almost never in a path that needs optimising ?
> I'd be amazed if any of this masturbation showed the tiniest
> blip on a real workload, or even on a benchmark other than
> one crafted specifically to test kfree in a loop.
>
I see kfree used in several hot paths. Check out
this /proc/latency_trace excerpt:
(T1/#147) ksoftirqd/0 2 0 2 00000002 00000093 [0038603486826120] 0.133ms (+0.000ms): preempt_schedule+0x11/0x80 <c02b5181> (rpc_wake_up_task+0x6c/0x80 <c02a802c>)
(T1/#148) ksoftirqd/0 2 0 2 00000001 00000094 [0038603486826375] 0.133ms (+0.000ms): preempt_schedule+0x11/0x80 <c02b5181> (udp_data_ready+0x1ca/0x270 <c02a5b8a>)
(T1/#149) ksoftirqd/0 2 0 2 00000001 00000095 [0038603486826527] 0.133ms (+0.000ms): skb_free_datagram+0xb/0x30 <c0257ecb> (udp_data_ready+0x19c/0x270 <c02a5b5c>)
(T1/#150) ksoftirqd/0 2 0 2 00000001 00000096 [0038603486826686] 0.133ms (+0.000ms): __kfree_skb+0xe/0xf0 <c0255bce> (udp_data_ready+0x19c/0x270 <c02a5b5c>)
(T1/#151) ksoftirqd/0 2 0 2 00000001 00000097 [0038603486826924] 0.133ms (+0.000ms): sock_rfree+0x8/0x20 <c0254648> (__kfree_skb+0x6b/0xf0 <c0255c2b>)
(T1/#152) ksoftirqd/0 2 0 2 00000001 00000098 [0038603486827082] 0.134ms (+0.000ms): kfree_skbmem+0xe/0x30 <c0255b9e> (__kfree_skb+0x76/0xf0 <c0255c36>)
(T1/#153) ksoftirqd/0 2 0 2 00000001 00000099 [0038603486827189] 0.134ms (+0.000ms): skb_release_data+0xd/0xd0 <c0255acd> (kfree_skbmem+0x19/0x30 <c0255ba9>)
(T1/#154) ksoftirqd/0 2 0 2 00000001 0000009a [0038603486827444] 0.134ms (+0.000ms): skb_drop_fraglist+0xc/0x50 <c0255a4c> (skb_release_data+0xa3/0xd0 <c0255b63>)
(T1/#155) ksoftirqd/0 2 0 2 00000001 0000009b [0038603486827573] 0.134ms (+0.000ms): __kfree_skb+0xe/0xf0 <c0255bce> (skb_drop_fraglist+0x35/0x50 <c0255a75>)
(T1/#156) ksoftirqd/0 2 0 2 00000001 0000009c [0038603486827733] 0.134ms (+0.000ms): kfree_skbmem+0xe/0x30 <c0255b9e> (__kfree_skb+0x76/0xf0 <c0255c36>)
(T1/#157) ksoftirqd/0 2 0 2 00000001 0000009d [0038603486827861] 0.134ms (+0.000ms): skb_release_data+0xd/0xd0 <c0255acd> (kfree_skbmem+0x19/0x30 <c0255ba9>)
(T1/#158) ksoftirqd/0 2 0 2 00000001 0000009e [0038603486828121] 0.134ms (+0.000ms): kfree+0x14/0x70 <c0143514> (kfree_skbmem+0x19/0x30 <c0255ba9>)
(T1/#159) ksoftirqd/0 2 0 2 00000001 0000009f [0038603486828671] 0.135ms (+0.000ms): kmem_cache_free+0x14/0x60 <c0143444> (kfree_skbmem+0x2a/0x30 <c0255bba>)
(T1/#160) ksoftirqd/0 2 0 2 00000001 000000a0 [0038603486829127] 0.135ms (+0.000ms): __kfree_skb+0xe/0xf0 <c0255bce> (skb_drop_fraglist+0x35/0x50 <c0255a75>)
(T1/#161) ksoftirqd/0 2 0 2 00000001 000000a1 [0038603486829341] 0.135ms (+0.000ms): kfree_skbmem+0xe/0x30 <c0255b9e> (__kfree_skb+0x76/0xf0 <c0255c36>)
(T1/#162) ksoftirqd/0 2 0 2 00000001 000000a2 [0038603486829469] 0.135ms (+0.000ms): skb_release_data+0xd/0xd0 <c0255acd> (kfree_skbmem+0x19/0x30 <c0255ba9>)
(T1/#163) ksoftirqd/0 2 0 2 00000001 000000a3 [0038603486829644] 0.135ms (+0.000ms): kfree+0x14/0x70 <c0143514> (kfree_skbmem+0x19/0x30 <c0255ba9>)
(T1/#164) ksoftirqd/0 2 0 2 00000001 000000a4 [0038603486829944] 0.136ms (+0.000ms): kmem_cache_free+0x14/0x60 <c0143444> (kfree_skbmem+0x2a/0x30 <c0255bba>)
(T1/#165) ksoftirqd/0 2 0 2 00000001 000000a5 [0038603486830243] 0.136ms (+0.000ms): __kfree_skb+0xe/0xf0 <c0255bce> (skb_drop_fraglist+0x35/0x50 <c0255a75>)
(T1/#166) ksoftirqd/0 2 0 2 00000001 000000a6 [0038603486830463] 0.136ms (+0.000ms): kfree_skbmem+0xe/0x30 <c0255b9e> (__kfree_skb+0x76/0xf0 <c0255c36>)
(T1/#167) ksoftirqd/0 2 0 2 00000001 000000a7 [0038603486830589] 0.136ms (+0.000ms): skb_release_data+0xd/0xd0 <c0255acd> (kfree_skbmem+0x19/0x30 <c0255ba9>)
(T1/#168) ksoftirqd/0 2 0 2 00000001 000000a8 [0038603486830800] 0.136ms (+0.000ms): kfree+0x14/0x70 <c0143514> (kfree_skbmem+0x19/0x30 <c0255ba9>)
(T1/#169) ksoftirqd/0 2 0 2 00000001 000000a9 [0038603486831083] 0.137ms (+0.000ms): kmem_cache_free+0x14/0x60 <c0143444> (kfree_skbmem+0x2a/0x30 <c0255bba>)
(T1/#170) ksoftirqd/0 2 0 2 00000001 000000aa [0038603486831394] 0.137ms (+0.000ms): __kfree_skb+0xe/0xf0 <c0255bce> (skb_drop_fraglist+0x35/0x50 <c0255a75>)
(T1/#171) ksoftirqd/0 2 0 2 00000001 000000ab [0038603486831608] 0.137ms (+0.000ms): kfree_skbmem+0xe/0x30 <c0255b9e> (__kfree_skb+0x76/0xf0 <c0255c36>)
(T1/#172) ksoftirqd/0 2 0 2 00000001 000000ac [0038603486831736] 0.137ms (+0.000ms): skb_release_data+0xd/0xd0 <c0255acd> (kfree_skbmem+0x19/0x30 <c0255ba9>)
(T1/#173) ksoftirqd/0 2 0 2 00000001 000000ad [0038603486831985] 0.137ms (+0.000ms): kfree+0x14/0x70 <c0143514> (kfree_skbmem+0x19/0x30 <c0255ba9>)
(T1/#174) ksoftirqd/0 2 0 2 00000001 000000ae [0038603486832443] 0.138ms (+0.000ms): kmem_cache_free+0x14/0x60 <c0143444> (kfree_skbmem+0x2a/0x30 <c0255bba>)
(T1/#175) ksoftirqd/0 2 0 2 00000001 000000af [0038603486832744] 0.138ms (+0.000ms): __kfree_skb+0xe/0xf0 <c0255bce> (skb_drop_fraglist+0x35/0x50 <c0255a75>)
(T1/#176) ksoftirqd/0 2 0 2 00000001 000000b0 [0038603486832880] 0.138ms (+0.000ms): kfree_skbmem+0xe/0x30 <c0255b9e> (__kfree_skb+0x76/0xf0 <c0255c36>)
Lee
next prev parent reply other threads:[~2005-03-29 2:53 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-03-25 22:08 [PATCH] no need to check for NULL before calling kfree() - fs/ext2/ Jesper Juhl
2005-03-25 22:29 ` linux-os
2005-03-25 22:44 ` Jesper Juhl
2005-03-26 7:50 ` Pekka Enberg
2005-03-26 8:32 ` Arjan van de Ven
2005-03-26 23:21 ` [PATCH] no need to check for NULL before calling kfree() -fs/ext2/ linux-os
2005-03-26 23:34 ` Marcin Dalecki
2005-03-27 2:00 ` Horst von Brand
2005-03-27 3:18 ` Marcin Dalecki
2005-03-27 22:12 ` linux-os
2005-03-26 23:54 ` Jesper Juhl
2005-03-27 0:05 ` Lee Revell
2005-03-27 10:55 ` Jesper Juhl
2005-03-27 14:56 ` Paul Jackson
2005-03-27 15:12 ` Jan Engelhardt
2005-03-27 17:40 ` Dave Jones
2005-03-27 18:17 ` Jan Engelhardt
2005-03-27 19:25 ` Pekka Enberg
2005-03-27 22:56 ` Jesper Juhl
2005-03-28 4:53 ` Paul Jackson
2005-03-30 18:57 ` Jesper Juhl
2005-03-28 1:20 ` Horst von Brand
2005-03-28 4:10 ` Paul Jackson
2005-03-28 12:58 ` Geert Uytterhoeven
2005-03-29 2:52 ` Lee Revell [this message]
2005-03-29 6:30 ` Pekka Enberg
2005-03-29 7:06 ` Jan Engelhardt
2005-03-29 7:24 ` Pekka J Enberg
2005-03-30 2:44 ` Paul Jackson
2005-03-30 6:13 ` Pekka J Enberg
2005-03-30 6:16 ` Paul Jackson
2005-03-30 7:15 ` P Lavin
2005-03-30 14:20 ` Jesper Juhl
2005-03-30 19:10 ` Jesper Juhl
2005-04-09 2:21 ` Jesper Juhl
2005-03-28 4:07 ` [PATCH] " Paul Jackson
2005-03-27 8:45 ` Arjan van de Ven
2005-03-27 12:51 ` Denis Vlasenko
2005-03-27 14:28 ` Arjan van de Ven
2005-03-27 23:13 ` [PATCH] no need to check for NULL before calling kfree()-fs/ext2/ linux-os
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