Re: dirty md raid5 slab bio leak

[Neil Brown <neilb@cse.unsw.edu.au>]

On Monday June 27, list-lkml@net4u.de wrote:
> Moin.
> 
> The machine:
> 
> amd64, 2G mem, 4 SATA disks on SiI 3114 [SATALink/SATARaid] Serial ATA 
> Controller, configured as md raid5/raid1, using [cfq-scheduler], running 
> 2.6.12-rc6 (application postgresql)
> 
> The story:
> 
> This morning the machine was very slow, first check shows that the machine 
> swaps and all disk i/o are very slow.
> 
> Looking further slabtop shows
> 
>  Active / Total Objects (% used)    : 19821561 / 19828316 (100.0%)
>  Active / Total Slabs (% used)      : 369737 / 369739 (100.0%)
>  Active / Total Caches (% used)     : 80 / 120 (66.7%)
>  Active / Total Size (% used)       : 1415795.50K / 1416586.19K (99.9%)
>  Minimum / Average / Maximum Object : 0.02K / 0.07K / 128.00K
> 
>   OBJS ACTIVE  USE OBJ SIZE  SLABS OBJ/SLAB CACHE SIZE NAME
> 9865575 9864690  99%    0.02K  43847      225    175388K biovec-1
> 9865254 9864654  99%    0.12K 318234       31   1272936K bio


raid5 never allocates from these slabs, so this cannot be a raid5
problem.
raid1 does, and you mention in the intro that raid1 might be involved,
but there are now more details...
Could you say a little bit more about your setup.. How are each of
raid1 and raid5 used.  Was there any error on a drive involved in raid1?

I just checked my test machine (running 2.6.12-rc3-mm3) and it had a
really large number of bio and biovec-1 in use too (and it's been
sitting fairly idle for several days).

I've quickly reviewed the raid1 code and I cannot see a bio leak
(though that doesn't mean there isn't one..)

If anyone else has a large 'bio' slab, please report the configuration
(kernel, is md in use, etc).

NeilBrown
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