lkml.org 
[lkml]   [2006]   [Aug]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH 1/2]: powerpc/cell spidernet bottom half
From
On Wed, Aug 16, 2006 at 04:32:52PM -0700, David Miller wrote:
> From: linas@austin.ibm.com (Linas Vepstas)
> > Why would you want to do this? It seems like a cruddier strategy
> > than what we can already do (which is to never get an transmit
> > interrupt, as long as the kernel can shove data into the device fast
> > enough to keep the queue from going empty.) The whole *point* of a
> > low-watermark interrupt is to never have to actually get the interrupt,
> > if the rest of the system is on its toes and is supplying data fast
> > enough.
>
> As long as TX packets get freed within a certain latency
> boundary, this kind of scheme should be fine.

I just had some fun making sure I wasn't making a liar out of myself.
So far, I'm good.

Did

echo 768111 > /proc/sys/net/core/wmem_max
echo 768111 > /proc/sys/net/core/wmem_default
to make sure that the app never blocked on a full socket.

(If the socket is small, then the app blocks,
the transmit queue drains, and we do get an interupt --
about 1K/sec, which is what is expected).

Ran 'vmstat 10' to watch the interrupts in real time.
Ran netperf, got 904 Mbits/sec, and *no* interrupts.
Yahoo!

Ran oprofile to see where he time went:

CPU: ppc64 Cell Broadband Engine, speed 3200 MHz (estimated)
Counted CYCLES events (Processor Cycles) with a unit mask of 0x00 (No unit mask) count 100000
samples % image name app name symbol name
13748742 77.6620 vmlinux-2.6.18-rc2 vmlinux-2.6.18-rc2 .cbe_idle
936172 5.2881 vmlinux-2.6.18-rc2 vmlinux-2.6.18-rc2 .__copy_tofrom_user
569353 3.2161 spidernet.ko spidernet .spider_net_xmit
450826 2.5466 spidernet.ko spidernet .spider_net_release_tx_chain
220374 1.2448 vmlinux-2.6.18-rc2 vmlinux-2.6.18-rc2 ._spin_unlock_irqrestore
112432 0.6351 vmlinux-2.6.18-rc2 vmlinux-2.6.18-rc2 ._spin_lock
91328 0.5159 vmlinux-2.6.18-rc2 vmlinux-2.6.18-rc2 .__qdisc_run
84804 0.4790 vmlinux-2.6.18-rc2 vmlinux-2.6.18-rc2 .packet_sendmsg
76167 0.4302 vmlinux-2.6.18-rc2 vmlinux-2.6.18-rc2 .kfree
74321 0.4198 vmlinux-2.6.18-rc2 vmlinux-2.6.18-rc2 .sock_alloc_send_skb
65323 0.3690 vmlinux-2.6.18-rc2 vmlinux-2.6.18-rc2 .kmem_cache_free
60334 0.3408 vmlinux-2.6.18-rc2 vmlinux-2.6.18-rc2 ._read_lock
60071 0.3393 vmlinux-2.6.18-rc2 vmlinux-2.6.18-rc2 .dev_queue_xmit
56900 0.3214 vmlinux-2.6.18-rc2 vmlinux-2.6.18-rc2 .kmem_cache_alloc_node
55281 0.3123 vmlinux-2.6.18-rc2 vmlinux-2.6.18-rc2 .sock_wfree
51242 0.2894 vmlinux-2.6.18-rc2 vmlinux-2.6.18-rc2 .dev_get_by_index
50438 0.2849 vmlinux-2.6.18-rc2 vmlinux-2.6.18-rc2 .compat_sys_socketcall
49247 0.2782 vmlinux-2.6.18-rc2 vmlinux-2.6.18-rc2 .fput
48589 0.2745 vmlinux-2.6.18-rc2 vmlinux-2.6.18-rc2 .sync_buffer
46055 0.2601 vmlinux-2.6.18-rc2 vmlinux-2.6.18-rc2 system_call_common
40607 0.2294 vmlinux-2.6.18-rc2 vmlinux-2.6.18-rc2 .local_bh_enable
40273 0.2275 vmlinux-2.6.18-rc2 vmlinux-2.6.18-rc2 .__might_sleep
38757 0.2189 vmlinux-2.6.18-rc2 vmlinux-2.6.18-rc2 .fget_light
38219 0.2159 vmlinux-2.6.18-rc2 vmlinux-2.6.18-rc2 .__kfree_skb
36804 0.2079 vmlinux-2.6.18-rc2 vmlinux-2.6.18-rc2 .sock_def_write_space
36443 0.2059 vmlinux-2.6.18-rc2 vmlinux-2.6.18-rc2 .skb_release_data
32174 0.1817 vmlinux-2.6.18-rc2 vmlinux-2.6.18-rc2 .sys_sendto
31828 0.1798 vmlinux-2.6.18-rc2 vmlinux-2.6.18-rc2 .sock_sendmsg
30676 0.1733 vmlinux-2.6.18-rc2 vmlinux-2.6.18-rc2 .pfifo_fast_dequeue
29607 0.1672 vmlinux-2.6.18-rc2 vmlinux-2.6.18-rc2 .add_event_entry
25870 0.1461 vmlinux-2.6.18-rc2 vmlinux-2.6.18-rc2 syscall_exit
25329 0.1431 vmlinux-2.6.18-rc2 vmlinux-2.6.18-rc2 .__alloc_skb
23885 0.1349 vmlinux-2.6.18-rc2 vmlinux-2.6.18-rc2 .__do_softirq
22046 0.1245 vmlinux-2.6.18-rc2 vmlinux-2.6.18-rc2 .kmem_find_general_cachep
21610 0.1221 vmlinux-2.6.18-rc2 vmlinux-2.6.18-rc2 .__dev_get_by_index
21059 0.1190 vmlinux-2.6.18-rc2 vmlinux-2.6.18-rc2 .dma_map_single
21044 0.1189 vmlinux-2.6.18-rc2 vmlinux-2.6.18-rc2 ._spin_lock_irqsave
20105 0.1136 vmlinux-2.6.18-rc2 vmlinux-2.6.18-rc2 .memset
.__copy_tofrom_user -- ouch spider does not currently do scatter-gather
.spider_net_xmit -- hmmm ?? why is it this large ??
.spider_net_release_tx_chain -- ?? a lot of time being spent cleaning up tx queues.
._spin_unlock_irqrestore -- hmm ? why so high? lock contention?

I presume the rest is normal.

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2006-08-17 02:25    [from the cache]
©2003-2011 Jasper Spaans