[9fans] checkarenas

[9fans] checkarenas

[Kenji Arisawa]

Hello,

I noticed strange output that I cann't understand.

term% cpu -h io
io% venti/checkarenas -v /dev/sdC0/arenas
arena='arena.0' [802816,537673728)
	version=4 created=1042806254 modified=1046935027 sealed
	score=d9da513c8906b67d118ffd862d3b6ffc098e2cd8
	clumps=93,052 compressed clumps=33,339 data=642,249,221 compressed data=530,978,181 disk storage=536,840,457

[snip]

arena='arena.29' [15570059264,16106930176)
	version=5 created=1202285650 modified=1238472397 sealed
	score=747a7af59246c9fac4d446c5060ad25b9ae6a317
	clumps=164,001 compressed clumps=113,952 data=873,264,264 compressed data=526,509,628 disk storage=536,841,691

arena='arena.30' [16106930176,16643801088)
	version=5 created=1233280267 modified=1243743100 sealed
	score=7a67bb47cd7cac4166b08b2f1931bc7dff23ef80
	clumps=312,611 compressed clumps=259,182 data=1,615,971,406 compressed data=517,139,649 disk storage=536,834,142

arena='arena.31' [16643801088,17180672000)
	version=5 created=1243743100 modified=1284116312
	clumps=25,827 compressed clumps=22,564 data=152,702,493 compressed data=70,866,487 disk storage=72,493,588

io% 

# note that arena.30 is sealed. #

on the otherhand,

term% import -k'user=arisawa' io / /n/io.import
term% venti/checkarenas -v /n/io.import/dev/sdC0/arenas
arena='arena.0' [802816,537673728)
	version=4 created=1042806254 modified=1046935027 sealed
	score=d9da513c8906b67d118ffd862d3b6ffc098e2cd8
	clumps=93,052 compressed clumps=33,339 data=642,249,221 compressed data=530,978,181 disk storage=536,840,457

[snip]

arena='arena.29' [15570059264,16106930176)
	version=5 created=1202285650 modified=1238472397 sealed
	score=747a7af59246c9fac4d446c5060ad25b9ae6a317
	clumps=164,001 compressed clumps=113,952 data=873,264,264 compressed data=526,509,628 disk storage=536,841,691

arena='arena.30' [16106930176,16643801088)
	version=5 created=1233280267 modified=1243743100
	score=7a67bb47cd7cac4166b08b2f1931bc7dff23ef80
	clumps=312,611 compressed clumps=259,182 data=1,615,971,406 compressed data=517,139,649 disk storage=536,834,142

arena='arena.31' [16643801088,17180672000)
	version=5 created=1243743100 modified=1284116312
	clumps=25,827 compressed clumps=22,564 data=152,702,493 compressed data=70,866,487 disk storage=72,493,588

term% 

# note that arena.30 is NOT sealed. #

the difference between two output is only in arena.30
I don't understand where the difference comes from.

I believe that /dev/sdC0/arenas on io and /n/io.import/dev/sdC0/arenas mounted on term must be same.
I also believe that
	venti/checkarenas -v file
consults only the given file.

Kenji Arisawa

Re: [9fans] checkarenas

[Russ Cox]

> I noticed strange output that I can't understand.

I can't understand it either.
It doesn't make any sense to me.
It might be interesting to run

cpu -h io
iostats venti/checkarenas -v /dev/sdC0/arenas arena.30

and see if the problem happens then.

The only thing I can think of is that
when run with something proxying the
9p connection, some reads return
less than the amount of data requested,
and venti is not correctly reissuing
the read for the remainder of the block.
That's a very scary thought.
The relevant function is /sys/src/cmd/venti/srv/part.c:/^prwb
but it looks okay.  Maybe there is some
bit of code that's not calling it.

Russ

Re: [9fans] checkarenas

[Kenji Arisawa]

Thank Russ,

>
> I can't understand it either.
> It doesn't make any sense to me.
> It might be interesting to run
>
> cpu -h io
> iostats venti/checkarenas -v /dev/sdC0/arenas arena.30
>
> and see if the problem happens then.

I have found the origin of the difference.
checkarenas command on term was older then that of io.
sorry for the fuss.

Kenji Arisawa