Re: Question about pool(9) sizes

[mlelstv%serpens.de@localhost (Michael van Elst)]

buhrow%nfbcal.org@localhost (Brian Buhrow) writes:

>Given the following snippet of output from vmstat -m, does the size 164,
>which I realize represents the number of objects in the pool, also
>represent the maximum  number of objects in the pool?


>Name        Size Requests Fail Releases Pgreq Pgrel Npage Hiwat Minpg Maxpg 
>Idle
>scxspl       164 67714659    0 67714659  2101  2092     9     9     1   inf 9

Size is not the number of objects in the pool.


A pool manages a set of equally sized items, for scxspl an item
is a scsipi_xfer structure.

Size     = the size of an item
Requests = number of item allocation attempts
Fail     = number of item allocation failures
Releases = number of item deallocations
Pgreq    = number of page allocation attempts
Pgrel    = number of page deallocations
Npage    = number of currently allocated pages
Nhiwat   = maximum number of allocated pages over pool lifetime
Minpg    = Minimum number of pages to keep
Maxpg    = limit to the number of pages that can be allocated (inf == no limit)
Idle     = Number of pages without item allocations


Maxpg determines the maximum pool size. Each page can contain
a fixed number of items which is about pagesize/itemsize,
the precise value depends on wether a page also includes
a header and on alignment restrictions of the item and
is a constant for the pool that isn't reported by vmstat.

If Fail > 0 then most likely the pool limit has been reached
in the past.

-- 
-- 
                                Michael van Elst
Internet: mlelstv%serpens.de@localhost
                                "A potential Snark may lurk in every tree."