Re: [RFC PATCH dm-ioband] Added in blktrace msgs for dm-ioband
From: Ryo Tsuruta
Date: Mon Apr 27 2009 - 05:44:32 EST
Hi Alan,
From: "Alan D. Brunelle" <Alan.Brunelle@xxxxxx>
Subject: [RFC PATCH dm-ioband] Added in blktrace msgs for dm-ioband
Date: Fri, 24 Apr 2009 17:47:37 -0400
> Hi Ryo -
>
> I don't know if you are taking in patches, but whilst trying to uncover
> some odd behavior I added some blktrace messages to dm-ioband-ctl.c. If
> you're keeping one code base for old stuff (2.6.18-ish RHEL stuff) and
> upstream you'll have to #if around these (the blktrace message stuff
> came in around 2.6.26 or 27 I think).
>
> My test case was to take a single 400GB storage device, put two 200GB
> partitions on it and then see what the "penalty" or overhead for adding
> dm-ioband on top. To do this I simply created an ext2 FS on each
> partition in parallel (two processes each doing a mkfs to one of the
> partitions). Then I put two dm-ioband devices on top of the two
> partitions (setting the weight to 100 in both cases - thus they should
> have equal access).
>
> Using default values I was seeing /very/ large differences - on the
> order of 3X. When I bumped the number of tokens to a large number
> (10,240) the timings got much closer (<2%). I have found that using
> weight-iosize performs worse than weight (closer to 5% penalty).
I could reproduce similar results. One dm-ioband device seems to stop
issuing I/Os for a few seconds at times. I'll investigate more on that.
> I'll try to formalize these results as I go forward and report out on
> them. In any event, I thought I'd share this patch with you if you are
> interested...
Thanks. I'll include your patche into the next release.
> Here's a sampling from some blktrace output (sorry for the wrapping) - I
> should note that I'm a bit scared to see such large numbers of holds
> going on when the token count should be >5,000 for each device...
> Holding these back in an equal access situation is inhibiting the block
> I/O layer to merge (most) of these (as mkfs performs lots & lots of
> small but sequential I/Os).
>
> ...
> 8,80 16 0 0.090651446 0 m N ioband 1 hold_nrm 1654
> 8,80 16 0 0.090653575 0 m N ioband 1 hold_nrm 1655
> 8,80 16 0 0.090655694 0 m N ioband 1 hold_nrm 1656
> 8,80 16 0 0.090657609 0 m N ioband 1 hold_nrm 1657
> 8,80 16 0 0.090659554 0 m N ioband 1 hold_nrm 1658
> 8,80 16 0 0.090661327 0 m N ioband 1 hold_nrm 1659
> 8,80 16 0 0.090666237 0 m N ioband 1 hold_nrm 1660
> 8,80 16 53036 0.090675081 4713 C W 391420657 + 1024 [0]
> 8,80 16 53037 0.090913365 4713 D W 392995569 + 1024
> [mkfs.ext2]
> 8,80 16 0 0.090950380 0 m N ioband 1 add_iss 1659 1659
> 8,80 16 0 0.090951296 0 m N ioband 1 add_iss 1658 1658
> 8,80 16 0 0.090951870 0 m N ioband 1 add_iss 1657 1657
> 8,80 16 0 0.090952416 0 m N ioband 1 add_iss 1656 1656
> 8,80 16 0 0.090952965 0 m N ioband 1 add_iss 1655 1655
> 8,80 16 0 0.090953517 0 m N ioband 1 add_iss 1654 1654
> 8,80 16 0 0.090954064 0 m N ioband 1 add_iss 1653 1653
> 8,80 16 0 0.090954610 0 m N ioband 1 add_iss 1652 1652
> 8,80 16 0 0.090955280 0 m N ioband 1 add_iss 1651 1651
> 8,80 16 0 0.090956495 0 m N ioband 1 pop_iss
> 8,80 16 53038 0.090957387 4659 A WS 396655745 + 8 <- (8,82)
> 6030744
> 8,80 16 53039 0.090957561 4659 Q WS 396655745 + 8 [kioband/16]
> 8,80 16 53040 0.090958328 4659 M WS 396655745 + 8 [kioband/16]
> 8,80 16 0 0.090959595 0 m N ioband 1 pop_iss
> 8,80 16 53041 0.090959754 4659 A WS 396655753 + 8 <- (8,82)
> 6030752
> 8,80 16 53042 0.090960007 4659 Q WS 396655753 + 8 [kioband/16]
> 8,80 16 53043 0.090960402 4659 M WS 396655753 + 8 [kioband/16]
> 8,80 16 0 0.090960962 0 m N ioband 1 pop_iss
> 8,80 16 53044 0.090961104 4659 A WS 396655761 + 8 <- (8,82)
> 6030760
> 8,80 16 53045 0.090961231 4659 Q WS 396655761 + 8 [kioband/16]
> 8,80 16 53046 0.090961496 4659 M WS 396655761 + 8 [kioband/16]
> 8,80 16 0 0.090961995 0 m N ioband 1 pop_iss
> 8,80 16 53047 0.090962117 4659 A WS 396655769 + 8 <- (8,82)
> 6030768
> 8,80 16 53048 0.090962222 4659 Q WS 396655769 + 8 [kioband/16]
> 8,80 16 53049 0.090962530 4659 M WS 396655769 + 8 [kioband/16]
> 8,80 16 0 0.090962974 0 m N ioband 1 pop_iss
> 8,80 16 53050 0.090963095 4659 A WS 396655777 + 8 <- (8,82)
> 6030776
> 8,80 16 53051 0.090963334 4659 Q WS 396655777 + 8 [kioband/16]
> 8,80 16 53052 0.090963518 4659 M WS 396655777 + 8 [kioband/16]
> 8,80 16 0 0.090963985 0 m N ioband 1 pop_iss
> 8,80 16 53053 0.090964220 4659 A WS 396655785 + 8 <- (8,82)
> 6030784
> 8,80 16 53054 0.090964327 4659 Q WS 396655785 + 8 [kioband/16]
> 8,80 16 53055 0.090964632 4659 M WS 396655785 + 8 [kioband/16]
> 8,80 16 0 0.090965094 0 m N ioband 1 pop_iss
> 8,80 16 53056 0.090965218 4659 A WS 396655793 + 8 <- (8,82)
> 6030792
> 8,80 16 53057 0.090965324 4659 Q WS 396655793 + 8 [kioband/16]
> 8,80 16 53058 0.090965548 4659 M WS 396655793 + 8 [kioband/16]
> 8,80 16 0 0.090965991 0 m N ioband 1 pop_iss
> 8,80 16 53059 0.090966112 4659 A WS 396655801 + 8 <- (8,82)
> 6030800
> 8,80 16 53060 0.090966221 4659 Q WS 396655801 + 8 [kioband/16]
> 8,80 16 53061 0.090966526 4659 M WS 396655801 + 8 [kioband/16]
> 8,80 16 0 0.090966944 0 m N ioband 1 pop_iss
> 8,80 16 53062 0.090967065 4659 A WS 396655809 + 8 <- (8,82)
> 6030808
> 8,80 16 53063 0.090967173 4659 Q WS 396655809 + 8 [kioband/16]
> 8,80 16 53064 0.090967383 4659 M WS 396655809 + 8 [kioband/16]
> 8,80 16 0 0.090968394 0 m N ioband 1 add_iss 1650 1650
> 8,80 16 0 0.090969068 0 m N ioband 1 add_iss 1649 1649
> 8,80 16 0 0.090969684 0 m N ioband 1 add_iss 1648 1648
> ...
>
> Regards,
> Alan D. Brunelle
> Hewlett-Packard
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