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
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