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'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...
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
>From bd918c40d92e4f074763a88bc8f13593c4f2dc52 Mon Sep 17 00:00:00 2001
From: Alan D. Brunelle <alan.brunelle@xxxxxx>
Date: Fri, 24 Apr 2009 17:30:32 -0400
Subject: [PATCH] Added in blktrace msgs for dm-ioband
Added the following messages:
In hold_bio - added messages as they are being added to either the
urgent or normal hold lists.
ioband <g_name> hold_urg <g_blocked>
ioband <g_name> hold_nrm <g_blocked>
In make_issue_list - added messages when placing previously held bios
onto either the pushback or issue lists:
ioband <g_name> add_pback <g_blocked> <c_blocked>
ioband <g_name> add_iss <g_blocked> <c_blocked>
In release_urgent bios - added a message indicating that an urgent bio
was added to the issue list:
ioband <g_name> urg_add_iss> <g_blocked>
In ioband_conduct - added messages as bios are being popped and executed
(sent to generic_make_request) or pushed back (bio_endio):
ioband <g_name> pop_iss
ioband <g_name> pop_pback
Signed-off-by: Alan D. Brunelle <alan.brunelle@xxxxxx>
---
drivers/md/dm-ioband-ctl.c | 30 +++++++++++++++++++++++++++---
1 files changed, 27 insertions(+), 3 deletions(-)
diff --git a/drivers/md/dm-ioband-ctl.c b/drivers/md/dm-ioband-ctl.c
index 29bef11..26ad7a5 100644
--- a/drivers/md/dm-ioband-ctl.c
+++ b/drivers/md/dm-ioband-ctl.c
@@ -13,6 +13,7 @@
#include <linux/slab.h>
#include <linux/workqueue.h>
#include <linux/rbtree.h>
+#include <linux/blktrace_api.h>
#include "dm.h"
#include "md.h"
#include "dm-bio-list.h"
@@ -633,9 +634,15 @@ static void hold_bio(struct ioband_group *gp, struct bio *bio)
*/
dp->g_prepare_bio(gp, bio, IOBAND_URGENT);
bio_list_add(&dp->g_urgent_bios, bio);
+ blk_add_trace_msg(bdev_get_queue(bio->bi_bdev),
+ "ioband %s hold_urg %d", dp->g_name,
+ dp->g_blocked);
} else {
gp->c_blocked++;
dp->g_hold_bio(gp, bio);
+ blk_add_trace_msg(bdev_get_queue(bio->bi_bdev),
+ "ioband %s hold_nrm %d", dp->g_name,
+ gp->c_blocked);
}
}
@@ -676,14 +683,21 @@ static int make_issue_list(struct ioband_group *gp, struct bio *bio,
clear_group_blocked(gp);
wake_up_all(&gp->c_waitq);
}
- if (should_pushback_bio(gp))
+ if (should_pushback_bio(gp)) {
bio_list_add(pushback_list, bio);
+ blk_add_trace_msg(bdev_get_queue(bio->bi_bdev),
+ "ioband %s add_pback %d %d", dp->g_name,
+ dp->g_blocked, gp->c_blocked);
+ }
else {
int rw = bio_data_dir(bio);
gp->c_stat[rw].deferred++;
gp->c_stat[rw].sectors += bio_sectors(bio);
bio_list_add(issue_list, bio);
+ blk_add_trace_msg(bdev_get_queue(bio->bi_bdev),
+ "ioband %s add_iss %d %d", dp->g_name,
+ dp->g_blocked, gp->c_blocked);
}
return prepare_to_issue(gp, bio);
}
@@ -703,6 +717,9 @@ static void release_urgent_bios(struct ioband_device *dp,
dp->g_blocked--;
dp->g_issued[bio_data_dir(bio)]++;
bio_list_add(issue_list, bio);
+ blk_add_trace_msg(bdev_get_queue(bio->bi_bdev),
+ "ioband %s urg_add_iss %d", dp->g_name,
+ dp->g_blocked);
}
}
@@ -916,10 +933,17 @@ static void ioband_conduct(struct work_struct *work)
spin_unlock_irqrestore(&dp->g_lock, flags);
- while ((bio = bio_list_pop(&issue_list)))
+ while ((bio = bio_list_pop(&issue_list))) {
+ blk_add_trace_msg(bdev_get_queue(bio->bi_bdev),
+ "ioband %s pop_iss", dp->g_name);
generic_make_request(bio);
- while ((bio = bio_list_pop(&pushback_list)))
+ }
+
+ while ((bio = bio_list_pop(&pushback_list))) {
+ blk_add_trace_msg(bdev_get_queue(bio->bi_bdev),
+ "ioband %s pop_pback", dp->g_name);
bio_endio(bio, -EIO);
+ }
}
static int ioband_end_io(struct dm_target *ti, struct bio *bio,
--
1.5.6.3
--
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