Re: [squid-users] again aio_queue_request

busy = "blocking" on most modern hardware. This due to quite large
request queue depths in modern SCSI drives.

A drive only have one active head. If there are 20 operations currently
being executed by the drive, the queue might be empty but still 19 of
those 20 operations are waiting, only that the OS does not know which.

For I/O performance measurement %busy and service time is the values
you are interested in. The "waiting" is more of a special case when
there are way too many applications banging against the same drive at
the same time.

--
Henrik Nordstrom
Squid hacker
Jens-Uwe Walther wrote:
> 
> Oops,
> 
> man iostat
> ...
>      %w        percent of time there are transactions waiting for
>                service (queue non-empty)
> 
>      %b        percent of time the disk is busy (transactions  in
>                progress)
> 
> says only that %b is busy not blocking.
> 
> So my cache_dir disk seems to be OK because %w is always 0.
> So is the problem the storage typ?
> 
>     0.8    1.5    4.2    9.6  0.0  0.2    0.0   66.3   0   2 c0t1d0
>     1.0   22.6    8.0  172.7  0.0 12.2    0.0  518.8   0  28 c0t1d0
>     0.0    1.4    0.0    4.2  0.0  0.0    0.0   22.9   0   1 c0t1d0
>     1.0   16.8    7.4  110.1  0.0  0.4    0.0   21.1   0  20 c0t1d0
>     0.8   12.2    6.4   73.8  0.0  0.4    0.0   31.3   0  11 c0t1d0
>     0.2    6.0    0.2   32.2  0.0  0.2    0.0   37.3   0   5 c0t1d0
>     0.6   10.0    4.6   55.0  0.0  0.6    0.0   60.5   0   8 c0t1d0
>     3.0   24.9   22.9  215.6  0.0  3.5    0.0  125.8   0  30 c0t1d0
>     0.0   22.5    0.0  203.6  0.0  0.7    0.0   29.7   0  16 c0t1d0
>     2.0   14.6    9.8  105.4  0.0  0.2    0.0   14.7   0  12 c0t1d0
>     0.4    9.6    3.2   88.2  0.0  0.2    0.0   17.2   0   7 c0t1d0
>     1.0    4.2    7.4   34.1  0.0  0.1    0.0   20.2   0   5 c0t1d0
> 
> My system is:
> 
> bash-2.03# uname -a
> SunOS sr-deu-proxy01 5.8 Generic_108528-02 sun4u sparc
> SUNW,UltraSPARC-IIi-Engine
> 
> bash-2.03# prtconf|more
> System Configuration:  Sun Microsystems  sun4u
> Memory size: 512 Megabytes
> 
> Squid 2.4STABLE1
> 
> Uwe