[gentoo-user] zcache + frontswap + cleancache: Am I missing something?

[gentoo-user] zcache + frontswap + cleancache: Am I missing something?

[Florian Philipp]

[-- Attachment #1: Type: text/plain, Size: 1821 bytes --]

Hi list!

I'm wondering about the usage of frontswap and cleancache. Now that all
pieces are in place in kernel-3.5, is it actually used?

I've found references to cleancache and frontswap in several source
files of the kernel (ext4, swapfile, page_io, ...).
/sys/kernel/mm/zcache is also present but seems to indicate no usage at
all. Content attached below.

So, what is the state of all this? Should it work? Does it work? Am I
missing a kernel parameter or something?

Content of /sys/kernel/mm/zcache:
compress_poor: 0
curr_obj_count: 0
curr_obj_count_max: 0
curr_objnode_count: 0
curr_objnode_count_max: 0
evicted_buddied_pages: 0
evicted_raw_pages: 0
evicted_unbuddied_pages: 0
failed_alloc: 0
failed_eph_puts: 0
failed_get_free_pages: 0
failed_pers_puts: 0
flobj_found: 0
flobj_total: 0
flush_found: 0
flush_total: 0
mean_compress_poor: 0
put_to_flush: 0
zbpg_unused_list_count: 0
zbud_buddied_count: 0
zbud_cumul_chunk_counts: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 <=21:0 <=32:0 <=42:0, mean:0
zbud_cumul_zbytes: 0
zbud_cumul_zpages: 0
zbud_curr_raw_pages: 0
zbud_curr_zbytes: 0
zbud_curr_zpages: 0
zbud_unbuddied_list_counts: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 zv_cumul_dist_counts: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 mean:0
zv_curr_dist_counts: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
mean:0
zv_max_mean_zsize: 2560
zv_max_zsize: 3584
zv_page_count_policy_percent: 75

Thanks in advance,
Florian Philipp


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 262 bytes --]

Re: [gentoo-user] zcache + frontswap + cleancache: Am I missing something?

[Kerin Millar]

Florian Philipp wrote:
> Hi list!
>
> I'm wondering about the usage of frontswap and cleancache. Now that all
> pieces are in place in kernel-3.5, is it actually used?
>
> I've found references to cleancache and frontswap in several source
> files of the kernel (ext4, swapfile, page_io, ...).
> /sys/kernel/mm/zcache is also present but seems to indicate no usage at
> all. Content attached below.

It might be that you have enabled some of these options as loadable 
modules: CONFIG_ZCACHE, CONFIG_CLEANCACHE and CONFIG_FRONTSWAP. If so, 
build them directly into the kernel image instead.

Cheers,

--Kerin

Re: [gentoo-user] zcache + frontswap + cleancache: Am I missing something?

[Florian Philipp]

[-- Attachment #1: Type: text/plain, Size: 869 bytes --]

Am 19.11.2012 18:51, schrieb Kerin Millar:
> Florian Philipp wrote:
>> Hi list!
>>
>> I'm wondering about the usage of frontswap and cleancache. Now that all
>> pieces are in place in kernel-3.5, is it actually used?
>>
>> I've found references to cleancache and frontswap in several source
>> files of the kernel (ext4, swapfile, page_io, ...).
>> /sys/kernel/mm/zcache is also present but seems to indicate no usage at
>> all. Content attached below.
> 
> It might be that you have enabled some of these options as loadable
> modules: CONFIG_ZCACHE, CONFIG_CLEANCACHE and CONFIG_FRONTSWAP. If so,
> build them directly into the kernel image instead.
> 
> Cheers,
> 
> --Kerin
> 

You cannot build these as modules. Anyway, I'm recompiling right now
with debugfs and configfs. Let's see if that tells me anything.

Regards,
Florian Philipp


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 262 bytes --]

Re: [gentoo-user] zcache + frontswap + cleancache: Am I missing something?

[Kerin Millar]

Florian Philipp wrote:
> Am 19.11.2012 18:51, schrieb Kerin Millar:
>> Florian Philipp wrote:
>>> Hi list!
>>>
>>> I'm wondering about the usage of frontswap and cleancache. Now that all
>>> pieces are in place in kernel-3.5, is it actually used?
>>>
>>> I've found references to cleancache and frontswap in several source
>>> files of the kernel (ext4, swapfile, page_io, ...).
>>> /sys/kernel/mm/zcache is also present but seems to indicate no usage at
>>> all. Content attached below.
>> It might be that you have enabled some of these options as loadable
>> modules: CONFIG_ZCACHE, CONFIG_CLEANCACHE and CONFIG_FRONTSWAP. If so,
>> build them directly into the kernel image instead.
>>
>> Cheers,
>>
>> --Kerin
>>
>
> You cannot build these as modules. Anyway, I'm recompiling right now
> with debugfs and configfs. Let's see if that tells me anything.
>
> Regards,
> Florian Philipp
>

Ah, good to know. I know that it was possible in some older kernels - 
while the feature was still in staging - but it must have since been fixed.

--Kerin

Re: [gentoo-user] zcache + frontswap + cleancache: Am I missing something?

[Florian Philipp]

[-- Attachment #1: Type: text/plain, Size: 1320 bytes --]

Am 19.11.2012 21:06, schrieb Kerin Millar:
> Florian Philipp wrote:
>> Am 19.11.2012 18:51, schrieb Kerin Millar:
>>> Florian Philipp wrote:
>>>> Hi list!
>>>>
>>>> I'm wondering about the usage of frontswap and cleancache. Now that all
>>>> pieces are in place in kernel-3.5, is it actually used?
>>>>
>>>> I've found references to cleancache and frontswap in several source
>>>> files of the kernel (ext4, swapfile, page_io, ...).
>>>> /sys/kernel/mm/zcache is also present but seems to indicate no usage at
>>>> all. Content attached below.
>>> It might be that you have enabled some of these options as loadable
>>> modules: CONFIG_ZCACHE, CONFIG_CLEANCACHE and CONFIG_FRONTSWAP. If so,
>>> build them directly into the kernel image instead.
>>>
>>> Cheers,
>>>
>>> --Kerin
>>>
>>
>> You cannot build these as modules. Anyway, I'm recompiling right now
>> with debugfs and configfs. Let's see if that tells me anything.
>>
>> Regards,
>> Florian Philipp
>>
> 
> Ah, good to know. I know that it was possible in some older kernels -
> while the feature was still in staging - but it must have since been fixed.
> 
> --Kerin
> 

Okay, fixed my issue. Turns out, you need to add a "zcache" kernel
parameter. Too bad there is no doc on this parameter.

Regards,
Florian Philipp


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 262 bytes --]