I see a very similar stall on writeout to ubd with my patches (easy) and
without (difficult - takes running an IO soak for a few days).
It stalls (usually) when trying to flush the journal file of ext4.
A.
On 14/10/14 08:21, Thomas Meyer wrote:
> Am Dienstag, den 14.10.2014, 07:43 +0100 schrieb Anton Ivanov:
>> On 14/10/14 06:38, Anton Ivanov wrote:
>>> How does the stall manifest itself?
>>>
>>> Do you have the journal thread (and sometimes a couple of other threads)
>>> sitting in D state?
>> Sorry, should not be asking questions at 6 am before the 3rd double
>> espresso.
>>
>> I think it is the same bug I am chasing - a stall in ubd, you hit it on
>> swap while I hit it in normal operation on a swapless system. I see a
>> stall in the journal instead of a backing dev stall.
>>
>> If you apply the ubd patches out of my patchsets, you can trigger this
>> one with ease. In theory, all they do is to make UBD faster so they
>> should not by themselves introduce new races. They may however make the
>> older ones more pronounced.
>>
>> My working hypothesis is a race somewhere in the vm subsystem. I have
>> been unable to nail it though.
> Hi Anton,
>
> I see this bug on a 3.17 uml kernel with the sync fix patch from
> Thorsten Knabe applied.
>
> The stall has to do with the writepage ratelimit mechanism, as the
> mechanism seems to reach a state where it tries to write out page, per
> page:
>
> Breakpoint 1, balance_dirty_pages (pages_dirtied=1, mapping=<optimized out>)
> at mm/page-writeback.c:1338
> (gdb) bt
> #0 balance_dirty_pages (pages_dirtied=1, mapping=<optimized out>) at
> mm/page-writeback.c:1338
>
> pages_dirtied = 1 !!
>
> #0 try_to_grab_pending (work=0x7fa2a348, is_dwork=true, flags=0x72ff5ab8) at
> kernel/workqueue.c:1159
> #1 0x0000000060051feb in mod_delayed_work_on (cpu=2141365064, wq=0x1,
> dwork=0x72ff5ab8, delay=<optimized out>) at kernel/workqueue.c:1510
> #2 0x00000000600f382c in mod_delayed_work (delay=<optimized out>,
> dwork=<optimized out>, wq=<optimized out>) at include/linux/workqueue.h:504
> #3 bdi_wakeup_thread (bdi=<optimized out>) at fs/fs-writeback.c:98
> #4 0x00000000600f4aca in bdi_start_background_writeback (bdi=<optimized
> out>) at fs/fs-writeback.c:179
> #5 0x000000006042d4c0 in balance_dirty_pages (pages_dirtied=<optimized out>,
> mapping=<optimized out>) at mm/page-writeback.c:1408
> #6 0x00000000600a6e1a in balance_dirty_pages_ratelimited (mapping=<optimized
> out>) at mm/page-writeback.c:1627
> #7 0x00000000600ba54f in do_wp_page (mm=<optimized out>, vma=<optimized
> out>, address=<optimized out>, page_table=<optimized out>, pmd=<optimized
> out>, orig_pte=..., ptl=<optimized out>) at mm/memory.c:2178
> #8 0x00000000600bc986 in handle_pte_fault (flags=<optimized out>,
> pmd=<optimized out>, pte=<optimized out>, address=<optimized out>,
> vma=<optimized out>, mm=<optimized out>) at mm/memory.c:3230
> #9 __handle_mm_fault (flags=<optimized out>, address=<optimized out>,
> vma=<optimized out>, mm=<optimized out>) at mm/memory.c:3335
> #10 handle_mm_fault (mm=<optimized out>, vma=0x7f653228, address=1472490776,
> flags=<optimized out>) at mm/memory.c:3364
> #11 0x0000000060028cec in handle_page_fault (address=1472490776,
> ip=<optimized out>, is_write=<optimized out>, is_user=0, code_out=<optimized
> out>) at arch/um/kernel/trap.c:75
> #12 0x00000000600290d7 in segv (fi=..., ip=1228924391, is_user=<optimized
> out>, regs=0x73eb8de8) at arch/um/kernel/trap.c:222
> #13 0x0000000060029395 in segv_handler (sig=<optimized out>,
> unused_si=<optimized out>, regs=<optimized out>) at arch/um/kernel/trap.c:191
> #14 0x0000000060039c0f in userspace (regs=0x73eb8de8) at
> arch/um/os-Linux/skas/process.c:429
> #15 0x0000000060026a8c in fork_handler () at arch/um/kernel/process.c:149
> #16 0x000000000070b620 in ?? ()
> #17 0x0000000000000000 in ?? ()
>
> I'm not sure if this is the same error you encounter.
>
> This is on an ubd device with a cow image attached to it.
>
> The original ubd file and the cow file are spares ones, and do also
> contain a swap partition.
>
> I hope to get tracepoints/perf working, now as there is stacktrace
> support in uml. An interessting tracepoint would be
> TRACE_EVENT(bdi_dirty_ratelimit) or TRACE_EVENT(balance_dirty_pages)
>
>
>> A.
>>
>>> A.
>>>
>>> On 13/10/14 22:48, Thomas Meyer wrote:
>>>> #0 balance_dirty_pages_ratelimited (mapping=0x792cc618) at
>>>> mm/page-writeback.c:1587
>>>> #1 0x00000000600ba54f in do_wp_page (mm=<optimized out>, vma=<optimized
>>>> out>, address=<optimized out>, page_table=<optimized out>, pmd
>>>> =<optimized out>, orig_pte=..., ptl=<optimized out>) at mm/memory.c:2178
>>>> #2 0x00000000600bc986 in handle_pte_fault (flags=<optimized out>,
>>>> pmd=<optimized out>, pte=<optimized out>, address=<optimized out>, v
>>>> ma=<optimized out>, mm=<optimized out>) at mm/memory.c:3230
>>>> #3 __handle_mm_fault (flags=<optimized out>, address=<optimized out>,
>>>> vma=<optimized out>, mm=<optimized out>) at mm/memory.c:3335
>>>> #4 handle_mm_fault (mm=<optimized out>, vma=0x78008e88,
>>>> address=1462695424, flags=<optimized out>) at mm/memory.c:3364
>>>> #5 0x0000000060028cec in handle_page_fault (address=1462695424,
>>>> ip=<optimized out>, is_write=<optimized out>, is_user=0, code_out=<opt
>>>> imized out>) at arch/um/kernel/trap.c:75
>>>> #6 0x00000000600290d7 in segv (fi=..., ip=1228924391, is_user=<optimized
>>>> out>, regs=0x624f5728) at arch/um/kernel/trap.c:222
>>>> #7 0x0000000060029395 in segv_handler (sig=<optimized out>,
>>>> unused_si=<optimized out>, regs=<optimized out>) at arch/um/kernel/trap.c:
>>>> 191
>>>> #8 0x0000000060039c0f in userspace (regs=0x624f5728) at
>>>> arch/um/os-Linux/skas/process.c:429
>>>> #9 0x0000000060026a8c in fork_handler () at arch/um/kernel/process.c:149
>>>> #10 0x0000000000000000 in ?? ()
>>>>
>>>> backing_dev_info:
>>>> p *mapping->backing_dev_info
>>>> $2 = {bdi_list = {next = 0x605901a0 <bdi_list>, prev = 0x80a42890},
>>>> ra_pages = 32, state = 8, capabilities = 4, congested_fn = 0x0, con
>>>> gested_data = 0x0, name = 0x604fb827 "block", bdi_stat = {{count = 4},
>>>> {count = 0}, {count = 318691}, {count = 314567}}, bw_time_stamp
>>>> = 4339445229, dirtied_stamp = 318686, written_stamp = 314564,
>>>> write_bandwidth = 166, avg_write_bandwidth = 164, dirty_ratelimit = 1, ba
>>>> lanced_dirty_ratelimit = 1, completions = {events = {count = 3}, period =
>>>> 4481, lock = {raw_lock = {<No data fields>}}}, dirty_exceeded
>>>> = 0, min_ratio = 0, max_ratio = 100, max_prop_frac = 1024, wb = {bdi =
>>>> 0x80a42278, nr = 0, last_old_flush = 4339445229, dwork = {work
>>>> = {data = {counter = 65}, entry = {next = 0x80a42350, prev = 0x80a42350},
>>>> func = 0x600f4b25 <bdi_writeback_workfn>}, timer = {entry = {
>>>> next = 0x606801a0 <boot_tvec_bases+4896>, prev = 0x803db650}, expires =
>>>> 4339445730, base = 0x6067ee82 <boot_tvec_bases+2>, function = 0
>>>> x60051dbb <delayed_work_timer_fn>, data = 2158240584, slack = -1}, wq =
>>>> 0x808d9c00, cpu = 1}, b_dirty = {next = 0x7a4ce1f8, prev = 0x80
>>>> 6ad9a8}, b_io = {next = 0x80a423c0, prev = 0x80a423c0}, b_more_io = {next
>>>> = 0x80a423d0, prev = 0x80a423d0}, list_lock = {{rlock = {raw_
>>>> lock = {<No data fields>}}}}}, wb_lock = {{rlock = {raw_lock = {<No data
>>>> fields>}}}}, work_list = {next = 0x80a423e0, prev = 0x80a423e0
>>>> }, dev = 0x80b68e00, laptop_mode_wb_timer = {entry = {next = 0x0, prev =
>>>> 0x0}, expires = 0, base = 0x6067ee80 <boot_tvec_bases>, functi
>>>> on = 0x600a6efd <laptop_mode_timer_fn>, data = 2158240008, slack = -1},
>>>> debug_dir = 0x80419e58, debug_stats = 0x80419d98}
>>>>
>>>> when i set the cap_dirty from the backing-dev ( capabilities = 5 ) the
>>>> system comes back to normal.
>>>>
>>>> any ideas what's going on here?
>>>>
>>>> with kind regards
>>>> thomas
>>>>
>>>>
>>>>
>>>> ------------------------------------------------------------------------------
>>>> Comprehensive Server Monitoring with Site24x7.
>>>> Monitor 10 servers for $9/Month.
>>>> Get alerted through email, SMS, voice calls or mobile push notifications.
>>>> Take corrective actions from your mobile device.
>>>> http://p.sf.net/sfu/Zoho
>>>> _______________________________________________
>>>> User-mode-linux-devel mailing list
>>>> User-mode-linux-devel@lists.sourceforge.net
>>>> https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel
>>>>
>>
>> ------------------------------------------------------------------------------
>> Comprehensive Server Monitoring with Site24x7.
>> Monitor 10 servers for $9/Month.
>> Get alerted through email, SMS, voice calls or mobile push notifications.
>> Take corrective actions from your mobile device.
>> http://p.sf.net/sfu/Zoho
>> _______________________________________________
>> User-mode-linux-devel mailing list
>> User-mode-linux-devel@lists.sourceforge.net
>> https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel
>
>
> ------------------------------------------------------------------------------
> Comprehensive Server Monitoring with Site24x7.
> Monitor 10 servers for $9/Month.
> Get alerted through email, SMS, voice calls or mobile push notifications.
> Take corrective actions from your mobile device.
> http://p.sf.net/sfu/Zoho
> _______________________________________________
> User-mode-linux-devel mailing list
> User-mode-linux-devel@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel
------------------------------------------------------------------------------
Comprehensive Server Monitoring with Site24x7.
Monitor 10 servers for $9/Month.
Get alerted through email, SMS, voice calls or mobile push notifications.
Take corrective actions from your mobile device.
http://p.sf.net/sfu/Zoho
_______________________________________________
User-mode-linux-devel mailing list
User-mode-linux-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel
