Ingo Molnar a écrit :
* Ingo Molnar <mingo@xxxxxxx> wrote:
4> The place for the sock_rfree() hit looks a bit weird, and i'll
investigate it now a bit more to place the real overhead point
properly. (i already mapped the test-bit overhead: that comes from
napi_disable_pending())
ok, here's a new set of profiles. (again for tbench 64-thread on a
16-way box, with v2.6.28-rc5-19-ge14c8bf and with the kernel config i
posted before.)
Here are the per major subsystem percentages:
NET overhead ( 5786945/10096751): 57.31%
security overhead ( 925933/10096751): 9.17%
usercopy overhead ( 837887/10096751): 8.30%
sched overhead ( 753662/10096751): 7.46%
syscall overhead ( 268809/10096751): 2.66%
IRQ overhead ( 266500/10096751): 2.64%
slab overhead ( 180258/10096751): 1.79%
timer overhead ( 92986/10096751): 0.92%
pagealloc overhead ( 87381/10096751): 0.87%
VFS overhead ( 53295/10096751): 0.53%
PID overhead ( 44469/10096751): 0.44%
pagecache overhead ( 33452/10096751): 0.33%
gtod overhead ( 11064/10096751): 0.11%
IDLE overhead ( 0/10096751): 0.00%
---------------------------------------------------------
left ( 753878/10096751): 7.47%
The breakdown is very similar to what i sent before, within noise.
[ 'left' is random overhead from all around the place - i categorized
the 500 most expensive functions in the profile per subsystem.
I stopped short of doing it for all 1300+ functions: it's rather
laborous manual work even with hefty use of regex patterns.
It's also less meaningful in practice: the trend in the first 500
functions is present in the remaining 800 functions as well. I
watched the breakdown evolve as i increased the coverage - in
practice it is the first 100 functions that matter - it just doesnt
change after that. ]
The readprofile output below seems structured in a more useful way now
- i tweaked compiler options to have the profiler hits spread out in a
more meaningful way. I collected 10 million NMI profiler hits, and
normalized the readprofile output up to 100%.
[ I'll post per function analysis as i complete them, as a reply to
this mail. ]
Ingo
100.000000 total
................
7.253355 copy_user_generic_string
3.934833 avc_has_perm_noaudit
3.356152 ip_queue_xmit
3.038025 skb_release_data
2.118525 skb_release_head_state
1.997533 tcp_ack
1.833688 tcp_recvmsg
1.717771 eth_type_trans
Strange, in my profile, eth_type_trans is not in the top 20
Maybe an alignment problem ?
Oh, I understand, you hit the netdevice->last_rx update probblem, already corrected on net-next-2.6
1.673249 __inet_lookup_established
TCP established/timewait table is now RCUified (for linux-2.6.29), this one
should go down in profiles.
1.508888 system_call
1.469183 tcp_current_mss
Yes there is a divide that might be expensive. discussion on netdev.
1.431553 tcp_transmit_skb
1.385125 tcp_sendmsg
1.327643 tcp_v4_rcv
1.292328 nf_hook_thresh
1.203205 schedule
1.059501 nf_hook_slow
1.027373 constant_test_bit
0.945183 sock_rfree
0.922748 __switch_to
0.911605 netif_rx
0.876270 register_gifconf
0.788200 ip_local_deliver_finish
0.781467 dev_queue_xmit
0.766530 constant_test_bit
0.758208 _local_bh_enable_ip
0.747184 load_cr3
0.704341 memset_c
0.671260 sysret_check
0.651845 ip_finish_output2
0.620204 audit_free_names
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