btrfs-ino-cache is running on each reboot

btrfs-ino-cache is running on each reboot

[dima]

Hello all,

About a week or so ago I noticed that [btrfs-ino-cache] process was 
appearing in the 'top' on each reboot and disk is spinning like crazy 
for about five minutes or so. Quite so often this caused X failing to 
start because all I/O was busy with caching.
Even after letting it to calm down and seeing [btrfs-ino-cache] 
disappearing from the process list, on next reboot it starts all over again.

Here is the fstab entry that I have

UUID=430dca92-9541-4201-0f62-373e30beadac / btrfs 
subvol=root_subvolume,defaults,noatime,noacl,compress=lzo,inode_cache,space_cache,autodefrag 
0 0

inode_cache was always enabled since the FS was created about a year or 
so ago, and actually I have never had any problems with it up until 
recently.

Removing inode_cache option from fstab solves the problem, but I am not 
sure if it is the right choice.
I can observe the problem at least in the vanilla kernel 3.10.4 ~ 6 (did 
not try older versions)

What could be the reason for such behavior and how to avoid it?

thanks

Re: btrfs-ino-cache is running on each reboot

[Duncan]

dima posted on Tue, 13 Aug 2013 10:28:59 +0900 as excerpted:

> About a week or so ago I noticed that [btrfs-ino-cache] process was
> appearing in the 'top' on each reboot and disk is spinning like crazy
> for about five minutes or so. Quite so often this caused X failing to
> start because all I/O was busy with caching.
> Even after letting it to calm down and seeing [btrfs-ino-cache]
> disappearing from the process list, on next reboot it starts all over
> again.

> inode_cache was always enabled since the FS was created about a year or
> so ago, and actually I have never had any problems with it up until
> recently.
> 
> Removing inode_cache option from fstab solves the problem, but I am not
> sure if it is the right choice.

A number of people have reported problems with inode_cache enabled, and 
the recommendation has always been to turn it off "unless you need it".  
Easy enough problem to fix, I guess. =:^)

Of course that immediately invites the question of why have the option at 
all if all it does is cause trouble, and (as a user not a dev) I don't 
have the answer to that.  I don't know the use case when "unless you need 
it" would actually apply, but apparently, it does in some cases.

I guess the wiki[1] should really have a warning on that option, but 
without a more solid reason than "just don't turn it on, causes more 
trouble than it's worth", I'd feel kind of goofy adding it.

Anyway, yes, the general recommendation on the list at this point seems 
to be to simply leave inode_cache off and not worry about it.

---
[1] https://btrfs.wiki.kernel.org/

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman

Re: btrfs-ino-cache is running on each reboot

[dima]

On 08/13/2013 01:09 PM, Duncan wrote:
> dima posted on Tue, 13 Aug 2013 10:28:59 +0900 as excerpted:
>
>> About a week or so ago I noticed that [btrfs-ino-cache] process was
>> appearing in the 'top' on each reboot and disk is spinning like crazy
>> for about five minutes or so. Quite so often this caused X failing to
>> start because all I/O was busy with caching.
>> Even after letting it to calm down and seeing [btrfs-ino-cache]
>> disappearing from the process list, on next reboot it starts all over
>> again.
>
>> inode_cache was always enabled since the FS was created about a year or
>> so ago, and actually I have never had any problems with it up until
>> recently.
>>
>> Removing inode_cache option from fstab solves the problem, but I am not
>> sure if it is the right choice.
>
> A number of people have reported problems with inode_cache enabled, and
> the recommendation has always been to turn it off "unless you need it".
> Easy enough problem to fix, I guess. =:^)
>
> Of course that immediately invites the question of why have the option at
> all if all it does is cause trouble, and (as a user not a dev) I don't
> have the answer to that.  I don't know the use case when "unless you need
> it" would actually apply, but apparently, it does in some cases.
>
> I guess the wiki[1] should really have a warning on that option, but
> without a more solid reason than "just don't turn it on, causes more
> trouble than it's worth", I'd feel kind of goofy adding it.
>
> Anyway, yes, the general recommendation on the list at this point seems
> to be to simply leave inode_cache off and not worry about it.


Thanks Duncan. So I did.
I was just wondering why it stopped behaving all of a sudden.



> ---
> [1] https://btrfs.wiki.kernel.org/
>

Re: btrfs-ino-cache is running on each reboot

[Josef Bacik]

On Tue, Aug 13, 2013 at 10:28:59AM +0900, dima wrote:
> Hello all,
> 
> About a week or so ago I noticed that [btrfs-ino-cache] process was
> appearing in the 'top' on each reboot and disk is spinning like crazy for
> about five minutes or so. Quite so often this caused X failing to start
> because all I/O was busy with caching.
> Even after letting it to calm down and seeing [btrfs-ino-cache] disappearing
> from the process list, on next reboot it starts all over again.
> 
> Here is the fstab entry that I have
> 
> UUID=430dca92-9541-4201-0f62-373e30beadac / btrfs subvol=root_subvolume,defaults,noatime,noacl,compress=lzo,inode_cache,space_cache,autodefrag
> 0 0
> 
> inode_cache was always enabled since the FS was created about a year or so
> ago, and actually I have never had any problems with it up until recently.
> 
> Removing inode_cache option from fstab solves the problem, but I am not sure
> if it is the right choice.
> I can observe the problem at least in the vanilla kernel 3.10.4 ~ 6 (did not
> try older versions)
> 
> What could be the reason for such behavior and how to avoid it?
> 

That's odd.  Can you apply patches and build kernels so I can try and narrow
down what is happening?  Thanks,

Josef

Re: btrfs-ino-cache is running on each reboot

[dima]

On 08/14/2013 12:37 AM, Josef Bacik wrote:
> On Tue, Aug 13, 2013 at 10:28:59AM +0900, dima wrote:
>> Hello all,
>>
>> About a week or so ago I noticed that [btrfs-ino-cache] process was
>> appearing in the 'top' on each reboot and disk is spinning like crazy for
>> about five minutes or so. Quite so often this caused X failing to start
>> because all I/O was busy with caching.
>> Even after letting it to calm down and seeing [btrfs-ino-cache] disappearing
>> from the process list, on next reboot it starts all over again.
>>
>> Here is the fstab entry that I have
>>
>> UUID=430dca92-9541-4201-0f62-373e30beadac / btrfs subvol=root_subvolume,defaults,noatime,noacl,compress=lzo,inode_cache,space_cache,autodefrag
>> 0 0
>>
>> inode_cache was always enabled since the FS was created about a year or so
>> ago, and actually I have never had any problems with it up until recently.
>>
>> Removing inode_cache option from fstab solves the problem, but I am not sure
>> if it is the right choice.
>> I can observe the problem at least in the vanilla kernel 3.10.4 ~ 6 (did not
>> try older versions)
>>
>> What could be the reason for such behavior and how to avoid it?
>>
>
> That's odd.  Can you apply patches and build kernels so I can try and narrow
> down what is happening?  Thanks,
>
> Josef
>

Hi Josef,
Sure, I can do that. I am running archlinux with a vanilla kernel that I 
build myself.
Thanks