Date: Tue, 6 Apr 2004 17:56:42 +1000 (EST) From: Andy Farkas <andyf@speednet.com.au> To: Xin LI <delphij@frontfree.net> Cc: freebsd-current@freebsd.org Subject: Re: Qustion about being "Giant-locked" Message-ID: <20040406174155.S56300@hewey.af.speednet.com.au> In-Reply-To: <20040406071205.GA2819@frontfree.net> References: <C192C8912E798F4399668791C8965190674FD6@mx.hhp.local> <009401c41ba5$3b000f70$0c00a8c0@artem> <20040406071205.GA2819@frontfree.net>
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On Tue, 6 Apr 2004, Xin LI wrote:
> On Tue, Apr 06, 2004 at 11:03:13AM +0400, Artem Koutchine wrote:
> > While booting i see many drivers marked
> > as [Giant-locked].
> > Is being Giant-locked good or bad what are the
> > implications?
> It's not good if you have a computer with multiple processors.
I have a box with 4 ppro-200 cpus. It has 4 adaptec eisa scsi controllers,
each controlling 2 disks. All 8 disks are in the same vinum raid-5 volume.
I have a large (1.5gig) file on this volume.
This is what happens when I run md5 on this file 4 times concurrently:
%%%
> md5 really-big-file &
[2] 78243
> md5 really-big-file &
[3] 78244
> md5 really-big-file &
[4] 78245
> md5 really-big-file &
[5] 78246
> vmstat -c10 -w6
procs memory page disks faults cpu
r b w avm fre flt re pi po fr sr ad0 am0 in sy cs us sy id
1 2 3 73308 28668 235 1 1 0 255 16 0 0 362 390 829 8 4 88
1 2 3 73308 21300 0 0 0 0 310 0 0 0 382 5928 11671 8 28 64
1 1 3 73308 29248 0 0 0 0 323 653 0 0 384 5769 11363 8 27 65
2 2 2 73308 20592 31 0 1 0 393 0 2 0 423 5614 11226 8 28 64
2 2 2 73308 27968 0 0 0 0 347 653 1 0 420 5655 11352 7 29 64
2 3 2 73308 19940 0 0 0 0 335 0 0 0 385 5563 11108 7 28 65
2 3 2 73308 26788 0 0 0 0 369 654 0 0 391 5608 11168 8 27 65
2 2 2 73308 34112 0 0 0 0 354 653 0 0 391 5656 11352 8 28 64
2 3 2 73308 25064 0 0 0 0 375 0 0 0 393 5687 11315 8 27 65
2 3 2 73308 32512 0 0 0 0 344 655 0 0 386 5664 11284 8 27 65
%%%
As you can see, only 8% of all cpus are being used to calculate the md5s.
At least 2 cpus are constantly idle.
> grep GIANT /var/run/dmesg.boot
fxp0: [GIANT-LOCKED]
ahc0: [GIANT-LOCKED]
ahc1: [GIANT-LOCKED]
ahc2: [GIANT-LOCKED]
ahc3: [GIANT-LOCKED]
amr0: [GIANT-LOCKED]
ahc4: [GIANT-LOCKED]
ahc5: [GIANT-LOCKED]
atkbd0: [GIANT-LOCKED]
--
:{ andyf@speednet.com.au
Andy Farkas
System Administrator
Speednet Communications
http://www.speednet.com.au/
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