[Lustre-discuss] slow direct_io , slow journal .. in OST log

Lex lexluthor87 at gmail.com
Sun Jan 24 18:42:20 PST 2010


Hi list

I have one OSS with hadware info like this :

CPU Intel(R) xeon E5420 2.5 Ghz
Chipset intel 5000P
8GB RAM

With this OSS, we using 2 RAID-5 arrays as OSTs ( each has 4 x 1.5 TB hard
drive with RAID controller adaptec 5805 )

I worked quite smooth before, but, about 2 weeks ago, in /var/log/messages,
i saw many warning ( i thought so)  like this:

*Jan 25 08:41:23 OST6 kernel: Lustre:
9587:0:(filter_io_26.c:706:filter_commitrw_write()) lustre-OST0006: slow
direct_io 35s
Jan 25 08:41:34 OST6 kernel: Lustre:
9608:0:(filter_io_26.c:706:filter_commitrw_write()) lustre-OST0006: slow
direct_io 41s
Jan 25 08:41:34 OST6 kernel: Lustre:
9608:0:(filter_io_26.c:706:filter_commitrw_write()) Skipped 2 previous
similar messages
Jan 25 08:41:35 OST6 kernel: Lustre:
9645:0:(filter_io_26.c:706:filter_commitrw_write()) lustre-OST0006: slow
direct_io 43s
Jan 25 08:58:10 OST6 kernel: Lustre:
9646:0:(filter_io_26.c:706:filter_commitrw_write()) lustre-OST0006: slow
direct_io 31s
Jan 25 08:59:39 OST6 kernel: Lustre:
9609:0:(filter_io_26.c:706:filter_commitrw_write()) lustre-OST0006: slow
direct_io 30s
Jan 25 09:01:05 OST6 kernel: Lustre:
9587:0:(filter_io_26.c:706:filter_commitrw_write()) lustre-OST0006: slow
direct_io 33s
Jan 25 09:03:23 OST6 kernel: Lustre:
9633:0:(filter_io_26.c:706:filter_commitrw_write()) lustre-OST0006: slow
direct_io 32s
Jan 25 09:11:25 OST6 kernel: Lustre:
9585:0:(filter_io_26.c:706:filter_commitrw_write()) lustre-OST0006: slow
direct_io 36s*

I googled around and found that it's because a problem with oss_num_threads
and even though brought it down to 64 ( followed by the function i found in
the 1.8 manual: thread_number = RAM * CPU core / 128 MB, its value is 256  )


*options ost oss_num_threads=64*

It still didn't help.

I thought it was only the harmless warning but maybe wrong, our performance
is goes down quite heavily ( it's maybe because of other reason, but for
now, i am only doubting slow direct_io problem )

iostat -m 1 1
Linux 2.6.18-92.1.17.el5_lustre.1.8.0custom (OST6)      01/25/2010

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           0.01    0.02    2.86   25.01    0.00   72.10

Device:            tps    MB_read/s    MB_wrtn/s    MB_read    MB_wrtn
sda               1.30         0.01         0.00      11386       3469
sdb               1.30         0.01         0.00      11531       3469
sdc             131.50        *12.40*         0.26   11793218     249934
sdd             178.46        *18.00*         0.26   17124065     250334
md2               3.33         0.02         0.00      22915       2634
md1               0.00         0.00         0.00          0          0
md0               0.00         0.00         0.00          0          0
drbd3           480.10        *12.39*         0.26   11789047     249639
drbd6           565.85        *14.89*         0.26   14168452     249211


So, could anyone please tell me whether it's warning impact our system
performance or not ? and if it does, give me solution or advice to resolve
it, please

Best regards
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