On 05/29/2015 04:42 PM, Dr. David Alan Gilbert wrote: > * zhanghailiang (zhang.zhanghailiang@xxxxxxxxxx) wrote: >> On 2015/5/29 9:29, Wen Congyang wrote: >>> On 05/29/2015 12:24 AM, Dr. David Alan Gilbert wrote: >>>> * zhanghailiang (zhang.zhanghailiang@xxxxxxxxxx) wrote: >>>>> This is the 5th version of COLO, here is only COLO frame part, include: VM checkpoint, >>>>> failover, proxy API, block replication API, not include block replication. >>>>> The block part has been sent by wencongyang: >>>>> "[Qemu-devel] [PATCH COLO-Block v5 00/15] Block replication for continuous checkpoints" >>>>> >>>>> we have finished some new features and optimization on COLO (As a development branch in github), >>>>> but for easy of review, it is better to keep it simple now, so we will not add too much new >>>>> codes into this frame patch set before it been totally reviewed. >>>>> >>>>> You can get the latest integrated qemu colo patches from github (Include Block part): >>>>> https://github.com/coloft/qemu/commits/colo-v1.2-basic >>>>> https://github.com/coloft/qemu/commits/colo-v1.2-developing (more features) >>>>> >>>>> Please NOTE the difference between these two branch. >>>>> colo-v1.2-basic is exactly same with this patch series, which has basic features of COLO. >>>>> Compared with colo-v1.2-basic, colo-v1.2-developing has some optimization in the >>>>> process of checkpoint, including: >>>>> 1) separate ram and device save/load process to reduce size of extra memory >>>>> used during checkpoint >>>>> 2) live migrate part of dirty pages to slave during sleep time. >>>>> Besides, we add some statistic info in colo-v1.2-developing, which you can get these stat >>>>> info by using command 'info migrate'. >>>> >>>> >>>> Hi, >>>> I have that running now. >>>> >>>> Some notes: >>>> 1) The colo-proxy is working OK until qemu quits, and then it gets an RCU problem; see below >>>> 2) I've attached some minor tweaks that were needed to build with the 4.1rc kernel I'm using; >>>> they're very minor changes and I don't think related to (1). >>>> 3) I've also included some minor fixups I needed to get the -developing world >>>> to build; my compiler is fussy about unused variables etc - but I think the code >>>> in ram_save_complete in your -developing patch is wrong because there are two >>>> 'pages' variables and the one in the inner loop is the only one changed. >> >> Oops, i will fix them. thank you for pointing out this low grade mistake. :) > > No problem; we all make them. > >>>> 4) I've started trying simple benchmarks and tests now: >>>> a) With a simple web server most requests have very little overhead, the comparison >>>> matches most of the time; I do get quite large spikes (0.04s->1.05s) which I guess >>>> corresponds to when a checkpoint happens, but I'm not sure why the spike is so big, >>>> since the downtime isn't that big. >> >> Have you disabled DEBUG for colo proxy? I turned it on in default, is this related? > > Yes, I've turned that off, I still get the big spikes; not looked why yet. > >>>> b) I tried something with more dynamic pages - the front page of a simple bugzilla >>>> install; it failed the comparison every time; it took me a while to figure out >> >> Failed comprison ? Do you mean the net packets in these two sides are always inconsistent? > > Yes. > >>>> why, but it generates a unique token in it's javascript each time (for a password reset >>>> link), and I guess the randomness used by that doesn't match on the two hosts. >>>> It surprised me, because I didn't expect this page to have much randomness >>>> in. >>>> >>>> 4a is really nice - it shows the benefit of COLO over the simple checkpointing; >>>> checkpoints happen very rarely. >>>> >>>> The colo-proxy rcu problem I hit shows as rcu-stalls in both primary and secondary >>>> after the qemu quits; the backtrace of the qemu stack is: >>> >>> How to reproduce it? Use monitor command quit to quit qemu? Or kill the qemu? >>> >>>> >>>> [<ffffffff810d8c0c>] wait_rcu_gp+0x5c/0x80 >>>> [<ffffffff810ddb05>] synchronize_rcu+0x45/0xd0 >>>> [<ffffffffa0a251e5>] colo_node_release+0x35/0x50 [nfnetlink_colo] >>>> [<ffffffffa0a25795>] colonl_close_event+0xe5/0x160 [nfnetlink_colo] >>>> [<ffffffff81090c96>] notifier_call_chain+0x66/0x90 >>>> [<ffffffff8109154c>] atomic_notifier_call_chain+0x6c/0x110 >>>> [<ffffffff815eee07>] netlink_release+0x5b7/0x7f0 >>>> [<ffffffff815878bf>] sock_release+0x1f/0x90 >>>> [<ffffffff81587942>] sock_close+0x12/0x20 >>>> [<ffffffff812193c3>] __fput+0xd3/0x210 >>>> [<ffffffff8121954e>] ____fput+0xe/0x10 >>>> [<ffffffff8108d9f7>] task_work_run+0xb7/0xf0 >>>> [<ffffffff81002d4d>] do_notify_resume+0x8d/0xa0 >>>> [<ffffffff81722b66>] int_signal+0x12/0x17 >>>> [<ffffffffffffffff>] 0xffffffffffffffff >>> >>> Thanks for your test. The backtrace is very useful, and we will fix it soon. >>> >> >> Yes, it is a bug, the callback function colonl_close_event() is called when holding >> rcu lock: >> netlink_release >> ->atomic_notifier_call_chain >> ->rcu_read_lock(); >> ->notifier_call_chain >> ->ret = nb->notifier_call(nb, val, v); >> And here it is wrong to call synchronize_rcu which will lead to sleep. >> Besides, there is another function might lead to sleep, kthread_stop which is called >> in destroy_notify_cb. >> >>>> >>>> that's with both the 423a8e268acbe3e644a16c15bc79603cfe9eb084 from yesterday and >>>> older e58e5152b74945871b00a88164901c0d46e6365e tags on colo-proxy. >>>> I'm not sure of the right fix; perhaps it might be possible to replace the >>>> synchronize_rcu in colo_node_release by a call_rcu that does the kfree later? >>> >>> I agree with it. >> >> That is a good solution, i will fix both of the above problems. > > Thanks, We have fix this problem, and test it. The patch is pushed to github, please try it. Thanks Wen Congyang > > Dave > >> >> Thanks, >> zhanghailiang >> >>> >>>> >>>> Thanks, >>>> >>>> Dave >>>> >>>>> >>> >>> >>> . >>> >> >> > -- > Dr. David Alan Gilbert / dgilbert@xxxxxxxxxx / Manchester, UK > -- > To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > . > -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
