Re: scsi-mq V2

From: Benjamin LaHaise
Date: Thu Jul 10 2014 - 10:45:47 EST


On Thu, Jul 10, 2014 at 02:36:40PM +0000, Elliott, Robert (Server Storage) wrote:
>
>
> > -----Original Message-----
> > From: Jens Axboe [mailto:axboe@xxxxxxxxx]
> > Sent: Thursday, 10 July, 2014 8:53 AM
> > To: Christoph Hellwig; Benjamin LaHaise
> > Cc: Elliott, Robert (Server Storage); dgilbert@xxxxxxxxxxxx; James Bottomley;
> > Bart Van Assche; linux-scsi@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> > Subject: Re: scsi-mq V2
> >
> > On 2014-07-10 15:50, Christoph Hellwig wrote:
> > > On Thu, Jul 10, 2014 at 09:36:09AM -0400, Benjamin LaHaise wrote:
> > >> There is one possible concern that could be exacerbated by other changes
> > in
> > >> the system: if the application is running close to the bare minimum number
> > >> of requests allocated in io_setup(), the per cpu reference counters will
> > >> have a hard time batching things. It might be worth testing with an
> > >> increased number of requests being allocated if this is the case.
> > >
> > > Well, Robert said reverting the two aio commits didn't help. Either he
> > > didn't manage to boot into the right kernel, or we need to look
> > > elsewhere for the culprit.
> >
> > Rob, let me know what scsi_debug setup you use, and I can try and
> > reproduce it here as well.
> >
> > --
> > Jens Axboe
>
> This system has 6 online CPUs and 64 possible CPUs.
>
> Printing avail and req_batch in that loop results in many of these:
> ** 3813 printk messages dropped ** [10643.503772] ctx ffff88042d8d4cc0 avail=0 req_batch=2
>
> Adding CFLAGS_aio.o := -DDEBUG to the Makefile to enable
> those pr_debug prints results in nothing extra printing,
> so it's not hitting an error.
>
> Printing nr_events and aio_max_nr at the top of ioctx_alloc results in
> these as fio starts:
>
> [ 186.339064] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 186.339065] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 186.339067] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 186.339068] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 186.339069] ioctx_alloc: nr_events=-2 aio_max_nr=65536

Something is horribly wrong here. There is no way that value for nr_events
should be passed in to ioctx_alloc(). This implies that userland is calling
io_setup() with an impossibly large value for nr_events. Can you post the
actual diff for your fs/aio.c relative to linus' tree?

-ben


> [ 186.339070] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 186.339071] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 186.339071] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 186.339074] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 186.339076] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 186.339076] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 186.359772] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 186.359971] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 186.359972] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 186.359985] sd 5:0:3:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 186.359986] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 186.359987] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 186.359995] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 186.359995] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 186.359998] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 186.359998] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 186.362529] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 186.362529] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 186.363510] sd 5:0:1:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 186.363513] sd 5:0:4:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 186.363520] sd 5:0:2:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 186.363521] sd 5:0:3:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 186.398113] sd 5:0:5:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 186.398115] sd 5:0:1:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 186.398121] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 186.398122] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 186.398124] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 186.398124] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 186.398130] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 186.398131] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 186.398164] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 186.398165] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 186.398499] sd 5:0:4:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 186.400489] sd 5:0:1:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 186.401478] sd 5:0:1:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 186.401491] sd 5:0:3:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 186.434522] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 186.434523] sd 5:0:3:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 186.434526] sd 5:0:5:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 186.434533] sd 5:0:0:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 186.435370] hrtimer: interrupt took 6868 ns
> [ 186.435491] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 186.435492] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 186.447864] sd 5:0:0:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 186.449896] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 186.449900] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 186.449901] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 186.449909] sd 5:0:0:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 186.449932] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 186.449933] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 186.461147] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 186.461176] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 186.461177] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 186.461181] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 186.461181] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 186.461184] sd 5:0:2:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 186.461185] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 186.461185] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 186.461191] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 186.461192] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 186.474426] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 186.481353] sd 5:0:1:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 186.483706] sd 5:0:2:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 186.483707] sd 5:0:0:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 186.483709] sd 5:0:4:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 186.483710] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 186.483712] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 186.483717] sd 5:0:2:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 186.495441] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 186.495444] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 186.495445] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 186.490] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 186.495451] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 186.495457] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 186.495457] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 186.495460] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 186.495461] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 186.495463] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 186.495464] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 186.499429] sd 5:0:4:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 186.499437] sd 5:0:5:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 186.619785] sd 5:0:4:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 186.627371] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 186.627374] sd 5:0:1:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 186.627383] sd 5:0:3:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 186.627384] sd 5:0:0:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 186.627385] sd 5:0:2:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 186.628371] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 186.628372] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 186.630361] sd 5:0:2:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 186.665329] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 186.666360] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 186.666361] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 186.666366] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 186.666367] sd 5:0:3:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 186.666367] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 186.666369] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 186.666370] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 186.670369] sd 5:0:5:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 186.670372] sd 5:0:5:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 186.670373] sd 5:0:5:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 186.767323] sd 5:0:4:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 187.211053] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 187.213053] sd 5:0:0:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
>
> Subsequent added prints showed nr_events coming in with
> an initial value of 0x7FFFFFFF in those cases where it showed
> as -2 above. Since the last call had a reasonable value
> of 512, it doesn't seem like a problem.
>
>
> script to create the scsi_debug devices:
> #!/bin/bash
> devices=6
> delay=0 # -2 = jiffy, -1 = hi jiffy, 0 = none, 1..n = longer
> ndelay=20000 # 20 us
> opts=0x4801 #
> every_nth=3
> capacity_mib=0
> capacity_gib=$((2 * 1024))
> lbpu=1
> lbpws=1
>
> modprobe -r scsi_debug
> modprobe -v scsi_debug fake_rw=1 delay=$delay ndelay=$ndelay num_tgts=$devices opts=$opts every_nth=$every_nth physblk_exp=3 lbpu=$lbpu lbpws=$lbpws dev_size_mb=$capacity_mib virtual_gb=$capacity_gib
> lsscsi -s
> lsblk
> # the assigned /dev names will vary...
> for device in /sys/block/sda[h-m]
> do
> echo none > $device/device/queue_type
> done
>
> fio script:
> [global]
> direct=1
> invalidate=1
> ioengine=libaio
> norandommap
> randrepeat=0
> bs=4096
> iodepth=96
> numjobs=6
> runtime=216000
> time_based=1
> group_reporting
> thread
> gtod_reduce=1
> iodepth_batch=16
> iodepth_batch_complete=16
> cpus_allowed=0-5
> cpus_allowed_policy=split
> rw=randread
>
> [4_KiB_RR_drive_ah]
> filename=/dev/sdah
>
> [4_KiB_RR_drive_ai]
> filename=/dev/sdai
>
> [4_KiB_RR_drive_aj]
> filename=/dev/sdaj
>
> [4_KiB_RR_drive_ak]
> filename=/dev/sdak
>
> [4_KiB_RR_drive_al]
> filename=/dev/sdal
>
> [4_KiB_RR_drive_am]
> filename=/dev/sdam
>
> kernel log with some prints in ioctx_alloc:
> (2147483647 is 0x7FFFFFFF)
>
> [ 94.050877] ioctx_alloc: initial nr_events=2147483647
> [ 94.053610] ioctx_alloc: num_possible_cpus=64
> [ 94.055235] ioctx_alloc: after max nr_events=2147483647
> [ 94.057110] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 94.059189] ioctx_alloc: initial nr_events=96
> [ 94.059294] ioctx_alloc: initial nr_events=2147483647
> [ 94.059295] ioctx_alloc: num_possible_cpus=64
> [ 94.059295] ioctx_alloc: after max nr_events=2147483647
> [ 94.059296] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 94.059296] ioctx_alloc: initial nr_events=96
> [ 94.059297] ioctx_alloc: num_possible_cpus=64
> [ 94.059297] ioctx_alloc: after max nr_events=256
> [ 94.059298] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 94.075891] ioctx_alloc: num_possible_cpus=64
> [ 94.077529] ioctx_alloc: after max nr_events=256
> [ 94.079064] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 94.087777] sd 5:0:0:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 94.087810] ioctx_alloc: initial nr_events=2147483647
> [ 94.087810] ioctx_alloc: num_possible_cpus=64
> [ 94.087811] ioctx_alloc: after max nr_events=2147483647
> [ 94.087811] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 94.087812] ioctx_alloc: initial nr_events=96
> [ 94.087812] ioctx_alloc: num_possible_cpus=64
> [ 94.087813] ioctx_alloc: after max nr_events=256
> [ 94.087813] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 94.087815] ioctx_alloc: initial nr_events=2147483647
> [ 94.087816] ioctx_alloc: initial nr_events=2147483647
> [ 94.087816] ioctx_alloc: num_possible_cpus=64
> [ 94.087817] ioctx_alloc: initial nr_events=2147483647
> [ 94.087818] ioctx_alloc: num_possible_cpus=64
> [ 94.087819] ioctx_alloc: after max nr_events=2147483647
> [ 94.087819] ioctx_alloc: num_possible_cpus=64
> [ 94.087820] ioctx_alloc: after max nr_events=2147483647
> [ 94.087820] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 94.087821] ioctx_alloc: after max nr_events=2147483647
> [ 94.087822] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 94.087822] ioctx_alloc: initial nr_events=96
> [ 94.087823] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 94.087824] ioctx_alloc: initial nr_events=96
> [ 94.087825] ioctx_alloc: initial nr_events=2147483647
> [ 94.087825] ioctx_alloc: num_possible_cpus=64
> [ 94.087826] ioctx_alloc: initial nr_events=96
> [ 94.087826] ioctx_alloc: num_possible_cpus=64
> [ 94.087827] ioctx_alloc: num_possible_cpus=64
> [ 94.087827] ioctx_alloc: after max nr_events=256
> [ 94.087828] ioctx_alloc: num_possible_cpus=64
> [ 94.087828] ioctx_alloc: after max nr_events=256
> [ 94.087829] ioctx_alloc: after max nr_events=2147483647
> [ 94.087829] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 94.087830] ioctx_alloc: after max nr_events=256
> [ 94.087831] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 94.087831] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 94.087832] ioctx_alloc: nr_events=512 aio_max_nr=65
> [ 94.087833] ioctx_alloc: initial nr_events=96
> [ 94.087833] ioctx_alloc: num_possible_cpus=64
> [ 94.087833] ioctx_alloc: after max nr_events=256
> [ 94.087834] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 94.090668] sd 5:0:0:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 94.259433] ioctx_alloc: initial nr_events=2147483647
> [ 94.259435] ioctx_alloc: initial nr_events=2147483647
> [ 94.259436] ioctx_alloc: num_possible_cpus=64
> [ 94.259437] ioctx_alloc: after max nr_events=2147483647
> [ 94.259437] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 94.259438] ioctx_alloc: initial nr_events=96
> [ 94.259438] ioctx_alloc: num_possible_cpus=64
> [ 94.259438] ioctx_alloc: after max nr_events=256
> [ 94.259439] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 94.259446] ioctx_alloc: initial nr_events=2147483647
> [ 94.259448] sd 5:0:2:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 94.259449] ioctx_alloc: initial nr_events=2147483647
> [ 94.259450] ioctx_alloc: initial nr_events=2147483647
> [ 94.259450] ioctx_alloc: num_possible_cpus=64
> [ 94.259451] ioctx_alloc: num_possible_cpus=64
> [ 94.259452] ioctx_alloc: num_possible_cpus=64
> [ 94.259452] ioctx_alloc: after max nr_events=2147483647
> [ 94.259453] ioctx_alloc: after max nr_events=2147483647
> [ 94.259453] ioctx_alloc: after max nr_events=2147483647
> [ 94.259454] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 94.259455] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 94.259455] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 94.259456] ioctx_alloc: initial nr_events=96
> [ 94.259456] ioctx_alloc: initial nr_events=96
> [ 94.259457] ioctx_alloc: initial nr_events=96
> [ 94.259457] ioctx_alloc: num_possible_cpus=64
> [ 94.259458] ioctx_alloc: num_possible_cpus=64
> [ 94.259458] ioctx_alloc: num_possible_cpus=64
> [ 94.259459] ioctx_alloc: after max nr_events=256
> [ 94.259459] ioctx_alloc: after max nr_events=256
> [ 94.259460] ioctx_alloc: after max nr_events=256
> [ 94.259460] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 259461] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 94.259462] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 94.260539] sd 5:0:5:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 94.260544] sd 5:0:4:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 94.262535] sd 5:0:2:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 94.262550] sd 5:0:3:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 94.423889] ioctx_alloc: num_possible_cpus=64
> [ 94.425386] ioctx_alloc: after max nr_events=2147483647
> [ 94.427327] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 94.429359] ioctx_alloc: initial nr_events=96
> [ 94.429448] sd 5:0:3:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 94.429451] ioctx_alloc: initial nr_events=2147483647
> [ 94.429452] sd 5:0:0:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 94.429453] ioctx_alloc: num_possible_cpus=64
> [ 94.429454] ioctx_alloc: initial nr_events=2147483647
> [ 94.429454] ioctx_alloc: after max nr_events=2147483647
> [ 94.429455] ioctx_alloc: num_possible_cpus=64
> [ 94.429456] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 94.429456] ioctx_alloc: after max nr_events=2147483647
> [ 94.429457] ioctx_alloc: initial nr_events=96
> [ 94.429458] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 94.429458] ioctx_alloc: num_possible_cpus=64
> [ 94.429459] ioctx_alloc: initial nr_events=96
> [ 94.429459] ioctx_alloc: after max nr_events=256
> [ 94.429460] ioctx_alloc: num_possible_cpus=64
> [ 94.429461] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 94.429461] ioctx_alloc: after max nr_events=256
> [ 94.429462] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 94.429463] sd 5:0:0:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 94.430422] hrtimer: interrupt took 6115 ns
> [ 94.431463] ioctx_alloc: initial nr_events=2147483647
> [ 94.431464] ioctx_alloc: num_possible_cpus=64
> [ 94.431464] ioctx_alloc: after max nr_events=2147483647
> [ 94.431465] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 94.431465] ioctx_alloc: initial nr_events=96
> [ 94.431466] ioctx_alloc: num_possible_cpus=64
> [ 931466] ioctx_alloc: after max nr_events=256
> [ 94.431466] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 94.432641] sd 5:0:2:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 94.580307] ioctx_alloc: num_possible_cpus=64
> [ 94.581844] ioctx_alloc: after max nr_events=256
> [ 94.583405] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 94.585313] sd 5:0:5:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 94.585319] ioctx_alloc: initial nr_events=2147483647
> [ 94.585320] ioctx_alloc: num_possible_cpus=64
> [ 94.585320] ioctx_alloc: after max nr_events=2147483647
> [ 94.585321] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 94.585322] ioctx_alloc: initial nr_events=2147483647
> [ 94.585322] ioctx_alloc: initial nr_events=96
> [ 94.585323] ioctx_alloc: num_possible_cpus=64
> [ 94.585324] ioctx_alloc: num_possible_cpus=64
> [ 94.585324] ioctx_alloc: after max nr_events=2147483647
> [ 94.585325] ioctx_alloc: after max nr_events=256
> [ 94.585325] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 94.585326] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 94.585327] ioctx_alloc: initial nr_events=2147483647
> [ 94.585328] ioctx_alloc: initial nr_events=96
> [ 94.585328] ioctx_alloc: num_possible_cpus=64
> [ 94.585329] ioctx_alloc: num_possible_cpus=64
> [ 94.585329] ioctx_alloc: after max nr_events=2147483647
> [ 94.585330] ioctx_alloc: after max nr_events=256
> [ 94.585331] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 94.585331] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 94.585332] ioctx_alloc: initial nr_events=96
> [ 94.585332] ioctx_alloc: num_possible_cpus=64
> [ 94.585333] ioctx_alloc: after max nr_events=256
> [ 94.585333] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 94.585372] sd 5:0:5:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 94.585402] sd 5:0:5:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 94.588377] sd 5:0:2:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 94.632221] ioctx_alloc: initial nr_events=2147483647
> [ 94.632228] ioctx_alloc: initial nr_events=2147483647
> [ 94.632229] iocalloc: num_possible_cpus=64
> [ 94.632229] ioctx_alloc: after max nr_events=2147483647
> [ 94.632230] ioctx_alloc: initial nr_events=2147483647
> [ 94.632231] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 94.632232] ioctx_alloc: num_possible_cpus=64
> [ 94.632232] ioctx_alloc: initial nr_events=96
> [ 94.632233] ioctx_alloc: after max nr_events=2147483647
> [ 94.632233] ioctx_alloc: num_possible_cpus=64
> [ 94.632234] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 94.632234] ioctx_alloc: after max nr_events=256
> [ 94.632235] ioctx_alloc: initial nr_events=96
> [ 94.632236] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 94.632236] ioctx_alloc: num_possible_cpus=64
> [ 94.632237] ioctx_alloc: after max nr_events=256
> [ 94.632237] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 94.632241] sd 5:0:0:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 94.633350] sd 5:0:3:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 94.764384] ioctx_alloc: num_possible_cpus=64
> [ 94.766038] ioctx_alloc: after max nr_events=2147483647
> [ 94.767807] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 94.769568] sd 5:0:5:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 94.770328] sd 5:0:0:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 94.773546] ioctx_alloc: initial nr_events=2147483647
> [ 94.773550] ioctx_alloc: initial nr_events=2147483647
> [ 94.773551] sd 5:0:1:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 94.773552] ioctx_alloc: num_possible_cpus=64
> [ 94.773552] ioctx_alloc: after max nr_events=2147483647
> [ 94.773553] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 94.773553] ioctx_alloc: initial nr_events=96
> [ 94.773554] ioctx_alloc: num_possible_cpus=64
> [ 94.773554] ioctx_alloc: after max nr_events=256
> [ 94.773555] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 94.773569] ioctx_alloc: initial nr_events=2147483647
> [ 94.773569] ioctx_alloc: num_possible_cpus=64
> [ 94.773570] ioctx_alloc: after max nr_events=2147483647
> [ 94.773570] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 94.773571] ioctx_alloc:itial nr_events=96
> [ 94.773571] ioctx_alloc: num_possible_cpus=64
> [ 94.773572] ioctx_alloc: after max nr_events=256
> [ 94.773572] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 94.903978] ioctx_alloc: num_possible_cpus=64
> [ 94.905427] ioctx_alloc: after max nr_events=2147483647
> [ 94.907320] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 94.909300] sd 5:0:3:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 94.909305] ioctx_alloc: initial nr_events=2147483647
> [ 94.909306] ioctx_alloc: num_possible_cpus=64
> [ 94.909306] ioctx_alloc: after max nr_events=2147483647
> [ 94.909307] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 94.909307] ioctx_alloc: initial nr_events=96
> [ 94.909308] ioctx_alloc: num_possible_cpus=64
> [ 94.909308] ioctx_alloc: after max nr_events=256
> [ 94.909309] ioctx_alloc: initial nr_events=2147483647
> [ 94.909310] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 94.909310] ioctx_alloc: num_possible_cpus=64
> [ 94.909311] ioctx_alloc: after max nr_events=2147483647
> [ 94.909311] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 94.909312] ioctx_alloc: initial nr_events=96
> [ 94.909312] ioctx_alloc: num_possible_cpus=64
> [ 94.909313] ioctx_alloc: after max nr_events=256
> [ 94.909313] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 94.912223] sd 5:0:1:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 94.940281] sd 5:0:4:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 94.940283] ioctx_alloc: initial nr_events=2147483647
> [ 94.940284] ioctx_alloc: num_possible_cpus=64
> [ 94.940285] ioctx_alloc: after max nr_events=2147483647
> [ 94.940286] ioctx_alloc: initial nr_events=2147483647
> [ 94.940286] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 94.940287] ioctx_alloc: num_possible_cpus=64
> [ 94.940288] ioctx_alloc: initial nr_events=96
> [ 94.940288] ioctx_alloc: after max nr_events=2147483647
> [ 94.940289] ioctx_alloc: num_possible_cpus=64
> [ 94.940290] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 94.940290] ioctx_alloc: after max nr_events=256
> [ 94.940291] ioctx_alloc: initial nr_events=96
> [ 94.940291] ioctx_alloc: nr_events=512 amax_nr=65536
> [ 94.940292] ioctx_alloc: num_possible_cpus=64
> [ 94.940292] ioctx_alloc: after max nr_events=256
> [ 94.940293] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 94.942198] sd 5:0:4:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 95.069096] ioctx_alloc: initial nr_events=96
> [ 95.069097] ioctx_alloc: num_possible_cpus=64
> [ 95.069097] ioctx_alloc: after max nr_events=256
> [ 95.069098] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 95.087101] ioctx_alloc: initial nr_events=2147483647
> [ 95.087108] ioctx_alloc: initial nr_events=2147483647
> [ 95.087108] ioctx_alloc: num_possible_cpus=64
> [ 95.087109] ioctx_alloc: after max nr_events=2147483647
> [ 95.087109] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 95.087110] ioctx_alloc: initial nr_events=96
> [ 95.087110] ioctx_alloc: num_possible_cpus=64
> [ 95.087111] ioctx_alloc: after max nr_events=256
> [ 95.087112] ioctx_alloc: initial nr_events=2147483647
> [ 95.087113] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 95.087113] ioctx_alloc: num_possible_cpus=64
> [ 95.087114] ioctx_alloc: after max nr_events=2147483647
> [ 95.087114] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 95.087115] ioctx_alloc: initial nr_events=96
> [ 95.087115] ioctx_alloc: num_possible_cpus=64
> [ 95.087116] ioctx_alloc: after max nr_events=256
> [ 95.087117] sd 5:0:1:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 95.087117] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 95.087120] ioctx_alloc: initial nr_events=2147483647
> [ 95.087120] ioctx_alloc: num_possible_cpus=64
> [ 95.087121] ioctx_alloc: after max nr_events=2147483647
> [ 95.087121] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 95.087122] ioctx_alloc: initial nr_events=96
> [ 95.087122] ioctx_alloc: num_possible_cpus=64
> [ 95.087123] ioctx_alloc: after max nr_events=256
> [ 95.087123] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 95.087126] sd 5:0:4:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 95.091100] ioctx_alloc: initial nr_events=2147483647
> [ 95.091100] ioctx_alloc: num_possible_cpus=64
> [ 95.091100] ioctx_alloc: after max nr_events=2147483647
> [ 95.091101] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 95.091101] ioctx_alloc: initial nr_events=96
> [ 95.091102] ioctx_alloc: num_possible_cpus=64
> [ 95.091102] ioctx_alloc: after max nr_events=256
> [ 95.091103] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 95.145236] ioctx_alloc: num_possible_cpus=64
> [ 95.146754] ioctx_alloc: after max nr_events=2483647
> [ 95.248567] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 95.250432] ioctx_alloc: initial nr_events=2147483647
> [ 95.250438] ioctx_alloc: initial nr_events=2147483647
> [ 95.250439] ioctx_alloc: num_possible_cpus=64
> [ 95.250439] ioctx_alloc: after max nr_events=2147483647
> [ 95.250440] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 95.250440] ioctx_alloc: initial nr_events=96
> [ 95.250441] ioctx_alloc: num_possible_cpus=64
> [ 95.250441] ioctx_alloc: after max nr_events=256
> [ 95.250442] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 95.250450] sd 5:0:5:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 95.250457] sd 5:0:2:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 95.251027] sd 5:0:1:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 95.251038] sd 5:0:1:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 95.252029] sd 5:0:3:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 95.275430] ioctx_alloc: num_possible_cpus=64
> [ 95.277000] ioctx_alloc: after max nr_events=2147483647
> [ 95.278747] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 95.280540] ioctx_alloc: initial nr_events=2147483647
> [ 95.280554] sd 5:0:4:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 95.284457] ioctx_alloc: num_possible_cpus=64
> [ 95.285998] ioctx_alloc: after max nr_events=2147483647
> [ 95.287764] ioctx_alloc: nr_events=-2 aio_max_nr=65536
> [ 95.289455] ioctx_alloc: initial nr_events=96
> [ 95.290901] ioctx_alloc: num_possible_cpus=64
> [ 95.292450] ioctx_alloc: after max nr_events=256
> [ 95.294013] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 95.295873] sd 5:0:3:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 95.381941] ioctx_alloc: initial nr_events=96
> [ 95.383764] ioctx_alloc: num_possible_cpus=64
> [ 95.385303] ioctx_alloc: after max nr_events=256
> [ 95.386959] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 95.391935] ioctx_alloc: initial nr_events=96
> [ 95.393493] ioctx_alloc: num_possible_cpus=64
> [ 95.394994] ioctx_alloc: after max nr_events=256
> [ 95.396751] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 95.421964] sd 5:0:2:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 95.425953] sd 5:0:4:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
> [ 95.611825] ioctx_alloc: initial nr_events=96
> [ 95.613398] ioctx_alloc: num_possible_cpus=64
> [ 95.614893] ioctx_alloc: after max nr_events=256
> [ 95.616615] ioctx_alloc: nr_events=512 aio_max_nr=65536
> [ 95.645844] sd 5:0:1:0: scsi_debug_ioctl: BLKFLSBUF [0x1261]
>

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