Re: Do I have to do anything to make sure ext4lazyinit works as being advertised ?
Hi all,
Please see below -
shirish शिरीष <shirishag75@gmail.com> writes:
> Dear Dmitry,
>
> I saw your patch about regression testing for ext4lazyinit
>
> https://patchwork.kernel.org/patch/9285509/ - that is where I got your mail id.
>
>
> I am a bit curious to know as to why the author/ess chose to
> keep 16 MB/S as the highest speed ?
>
> https://www.thomas-krenn.com/en/wiki/Ext4_Filesystem
Basically the article's statement is wrong.
There is no such thing as explicit itable initialization IO bandwidth
restriction in MB/s. itable initialization rate is controlled by init_itable=N
see: https://www.kernel.org/doc/Documentation/filesystems/ext4.txt
"""
The lazy itable init code will wait n times the
number of milliseconds it took to zero out the
previous block group's inode table. This
minimizes the impact on the system performance
while file system's inode table is being initialized.
"""
By default init_itable=10, so it use 1/10th bandwidth of the disk.
And if we back to original article this means author used generic
HDD with 160Mb/s sequential write performance.
My patch was fix for bug which was spotted on large disk arrays,
36 in my case. So itable initialization was active all the time
while holding global lock.
>From this, it seems there aren't any limits except for 10% of whatever
the link between
On 01/02/2017, shirish शिरीष <shirishag75@gmail.com> wrote:
> in-line :-
>
> On 01/02/2017, Lennart Sorensen <lsorense@csclub.uwaterloo.ca> wrote:
>> On Wed, Feb 01, 2017 at 12:46:48AM +0530, shirish शिरीष wrote:
>
> <snipped>
>
>>> Now I have few queries -
>>>
>>> a. Are my assumptions wrong ?
>>
>> About the doing the init on a future boot, yes you are wrong.
>
> Ah...ok.
>
> <snipped>
>
>>
>> 2.6.37 apparently.
>
> My bad ...
>
> <snipped>
>
>>
>> I believe it is on by default. However, the lazy init takes
>> place in the background on first mount (so that means during
>> the install), not some later boot. It apparently will use
>> up to 16MB/s for initializing in the background according to
>> https://www.thomas-krenn.com/en/wiki/Ext4_Filesystem
>>
>> I suspect it is already doing the best you are going to get.
>
> hmm.... From what little I understand, it always the slowest interface
> that needs to be supported.
>
> And IIUC , in ext4lazyinit's case it is probably some of the MMC cards
> due to which the 16 MB/S transmission is kept - although some of them
> are at 104 MB/S as well.
>
> https://en.wikipedia.org/wiki/MultiMediaCard#Table
>
> Whereas USB are at -
>
> https://en.wikipedia.org/wiki/USB_3.1
>
> USB 2.0 - 35 MB/S
>
> USB 3.0 - 400 MB/S
>
> USB 3.1 - Gen 1 - 400 MB/S
>
> USB 3.2 - Gen 2 - 1280 MB/S
>
> For HDD -
>
> https://en.wikipedia.org/wiki/Serial_ATA
>
> SATA 1 - starts at 150 MB/S
>
> Another query - if instead ext4lazyinit IF -
>
> mkfs.ext4 -E lazy_itable_init=0,lazy_journal_init=0 /dev/mapper/fc-root
>
> is applied then would it would start formatting and making inodes at a
> much faster rate - i.e. slowest between the USB Drive and HDD in a
> typical workstation - which probably would be a jump 3-4 times the
> speed that ext4lazyinit would employ.
>
> WDYT ?
>
> If yes, how as a user could I apply/use the above command while using
> debian-installer ?
>
>> --
>> Len Sorensen
>>
>
>
> --
> Regards,
> Shirish Agarwal शिरीष अग्रवाल
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>
--
Regards,
Shirish Agarwal शिरीष अग्रवाल
My quotes in this email licensed under CC 3.0
http://creativecommons.org/licenses/by-nc/3.0/
http://flossexperiences.wordpress.com
EB80 462B 08E1 A0DE A73A 2C2F 9F3D C7A4 E1C4 D2D8
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