Re: long hangs when deleting large directories (3.0-rc3)

[Dave Chinner <david@fromorbit.com>]

On Mon, Jun 20, 2011 at 02:54:15AM +0200, Markus Trippelsdorf wrote:
> On 2011.06.20 at 08:24 +1000, Dave Chinner wrote:
> > On Sat, Jun 18, 2011 at 04:19:50PM +0200, Markus Trippelsdorf wrote:
> > > Running the latest git kernel (3.0-rc3) my machine hangs for long
> > > periods (1-2 sec) whenever I delete a large directory recursively on my
> > > xfs partition. During the hang I cannot move the mouse pointer or use
> > > the keyboard (but the music keeps playing without stuttering). A quick
> > > way to reproduce is to "rm -fr" a kernel tree. 
> > 
> > So what is the system doing when it "hangs"? Is it CPU bound (e.g.
> > cpu scheduler issue)? Is the system running out of memory and
> > stalling everything in memory reclaim? What IO is occurring?
> 
> It's totally idle otherwise; just a desktop with a single xterm. The
> machine has four cores (and also runs with "CONFIG_PREEMPT=y"), so I
> don't think it is CPU bound at all. It has 8GB of memory (and the
> "hangs" even occur after reboot when most of it is free). No other IO
> activity is occurring.

Sure, the system might be otherwise idle, but what I was asking is
what load does the "rm -rf" cause. What IO does it cause? is it cpu
bound? etc.

> > > This happens on a 4kb SATA hard drive:
> > 
> > How does this appear to the OS? as a 512/512, 512/4k or 4k/4k
> > logical/physical sector size drive?
> 
> It unfortunately appears as 512/512, but because I know it's a 4KB
> drive, I formated it with "-s size=4096".

Oh, joy. Another user having strange performance problems on a 4k
sector drive that lies to the OS about it's geometry....

> > > xfs_info /var
> > > meta-data=/dev/sda1              isize=256    agcount=4, agsize=12800000 blks
> > >          =                       sectsz=4096  attr=2
> > > data     =                       bsize=4096   blocks=51200000, imaxpct=25
> > >          =                       sunit=0      swidth=0 blks
> > > naming   =version 2              bsize=4096   ascii-ci=0
> > > log      =internal               bsize=4096   blocks=25000, version=2
> > >          =                       sectsz=4096  sunit=1 blks, lazy-count=1
> > > realtime =none                   extsz=4096   blocks=0, rtextents=0
> > > 
> > > /dev/sda1 on /var type xfs (rw,noatime,attr2,delaylog,logbsize=256k,noquota)
> > 
> > Is your partition correctly sector aligned for however your drive
> > maps it's 4k sectors?
> 
> Yes, it's a GPT partition that is aligned to 1MB.

Ok, that is fine, but the big question now is how does the drive
align sector 0? Is that 4k aligned, or is it one of those drives
that aligns an odd 512 byte logical sector to the physical 4k sector
boundary (i.e. sector 63 is 4k aligned to work with msdos
partitions). FYI, some drives have jumpers on them to change this
odd/even sector alignment configuration.....

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

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