Re: Nooby Q: Should this take five hours? And counting?

MG>take a look at the man page for vmstat

Martin Gainty
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> Date: Sat, 18 Apr 2009 18:55:59 -0600
> Subject: Re: [GENERAL] Nooby Q: Should this take five hours? And counting?
> From: scott(dot)marlowe(at)gmail(dot)com
> To: kentilton(at)gmail(dot)com
> CC: pgsql-general(at)postgresql(dot)org
>
> On Sat, Apr 18, 2009 at 6:32 PM, Kenneth Tilton <kentilton(at)gmail(dot)com> wrote:
> >
> >
> > Scott Marlowe wrote:
> >> On Sat, Apr 18, 2009 at 4:11 PM, Kenneth Tilton <kentilton(at)gmail(dot)com>
> >> wrote:
> >>> ie, 5hrs and counting, no clue how long it intends to run, but methinks
> >>> this
> >>> is insane even if it is 10^7 records, mebbe half a dozen dups per value
> >>> (a
> >>> product-id usually around 8-chars long):
> >>>
> >>> CREATE INDEX web_source_items_by_item_id_strip
> >>> ON web_source_items
> >>> USING btree (item_id_strip);
> >>>
> >>> Am I unreasonably impatient?
> >>>
> >>> I see pg getting just a few % CPU on a heavily ram/core-endowed Sun box
> >>> with
> >>> nothing else going on. Mebbe they installed pg on a compact flash?
> >>> DVD-RW?
> >>> /usr/local/something, prolly not.
> >>
> >> What does vmstat 1 60 say during the index build? Specifically the
> >> cpu columns for user, system, wa?
> >
> > uh-oh, Unix noob too, and unfortunately someone has jumped on with a
> > CPU-intensive task pegging one of the cores at 100%, so these numbers prolly
> > do not help, but here goes:
> >
> > procs -----------memory---------- ---swap-- -----io---- --system--
> > -----cpu------
FIELD DESCRIPTION FOR VM MODE Procs
r: The number of processes waiting for run time.
b: The number of processes in uninterruptible sleep.

Memory
swpd: the amount of virtual memory used.
free: the amount of idle memory.
buff: the amount of memory used as buffers.
cache: the amount of memory used as cache.
inact: the amount of inactive memory. (-a option)
active: the amount of active memory. (-a option)

Swap
si: Amount of memory swapped in from disk (/s).
so: Amount of memory swapped to disk (/s).

IO
bi: Blocks received from a block device (blocks/s).
bo: Blocks sent to a block device (blocks/s).

System
in: The number of interrupts per second, including the clock.
cs: The number of context switches per second.

CPU
These are percentages of total CPU time.
us: Time spent running non-kernel code. (user time, including nice time)
sy: Time spent running kernel code. (system time)
id: Time spent idle. Prior to Linux 2.5.41, this includes IO-wait time.
wa: Time spent waiting for IO. Prior to Linux 2.5.41, shown as zero.

> > r b swpd free buff cache si so bi bo in cs us sy id
> > wa st
> > 1 1 2076312 1503204 182152 30669308 49 69 260 299 3 3 28 2
> > 63 7 0
> > 1 1 2076312 1502900 182152 30669656 0 0 192 2260 1198 332 25 1
> > 50 24 0
> > 1 1 2076312 1503024 182152 30669656 0 0 0 704 1181 282 25 1
> > 50 25 0
> > 1 3 2076312 1502904 182156 30669740 0 0 104 2780 1224 422 25 0
> > 48 26 0
> > 1 3 2076312 1502896 182156 30669740 0 0 0 1552 1173 309 25 0
> >
> > I'll sample again if I get a window, but these jobs tend to run for hours.
>
> I'm gonna take a guess about a few things:
> 1: You've got a lot of memory in that machine, try cranking up
> work_mem for this query to see if that helps
> 2: You've got a slow disk subsystem, if you're already seeing 25%
> IOWait with only ~2 to 3 megs a second being written.
>
> While having enough memory for everything to fit in it makes for fast
> reads, it doesn't do a lot to help with writes.
>
> --
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