Btrfs experimental branch updates

Btrfs experimental branch updates

[Chris Mason]

Hello everyone,

I've rebased the experimental branch to include most of the
optimizations I've been working on.

The two major changes are doing all extent tree operations in delayed
processing queues and removing many of the blocking points with btree
locks held.

In addition to smoothing out IO performance, these changes really cut
down on the amount of stack btrfs is using, which is especially
important for kernels with 4k stacks enabled (fedora).

-chris

Re: Btrfs experimental branch updates

[Steven Pratt]

Chris Mason wrote:
> Hello everyone,
>
> I've rebased the experimental branch to include most of the
> optimizations I've been working on.
>
> The two major changes are doing all extent tree operations in delayed
> processing queues and removing many of the blocking points with btree
> locks held.
>
> In addition to smoothing out IO performance, these changes really cut
> down on the amount of stack btrfs is using, which is especially
> important for kernels with 4k stacks enabled (fedora).
>
>   
Well, no drastic changes.  On Raid, creates got better, but random write 
got worse. Mail server was mixed. For single disk, pretty much the same 
story, although CPU savings is noticeable on write, although at the 
expense of performance.

Raid graphs and links:
http://btrfs.boxacle.net/repository/raid/history/History.html

Single disk graphs and links:
http://btrfs.boxacle.net/repository/single-disk/History/History.html

Steve

> -chris
>
>
> --
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>   

Re: Btrfs experimental branch updates

[Chris Mason]

On Fri, 2009-03-13 at 17:52 -0500, Steven Pratt wrote:
> Chris Mason wrote:
> > Hello everyone,
> >
> > I've rebased the experimental branch to include most of the
> > optimizations I've been working on.
> >
> > The two major changes are doing all extent tree operations in delayed
> > processing queues and removing many of the blocking points with btree
> > locks held.
> >
> > In addition to smoothing out IO performance, these changes really cut
> > down on the amount of stack btrfs is using, which is especially
> > important for kernels with 4k stacks enabled (fedora).
> >
> >   
> Well, no drastic changes.  On Raid, creates got better, but random write 
> got worse. Mail server was mixed. For single disk, pretty much the same 
> story, although CPU savings is noticeable on write, although at the 
> expense of performance.
> 

Thanks for running this, but the main performance fixes for your test
are still in testing locally.  One thing that makes a huge difference on
the random write run is to mount -o ssd.

-chris

Re: Btrfs experimental branch updates

[Steven Pratt]

Chris Mason wrote:
> On Fri, 2009-03-13 at 17:52 -0500, Steven Pratt wrote:
>   
>> Chris Mason wrote:
>>     
>>> Hello everyone,
>>>
>>> I've rebased the experimental branch to include most of the
>>> optimizations I've been working on.
>>>
>>> The two major changes are doing all extent tree operations in delayed
>>> processing queues and removing many of the blocking points with btree
>>> locks held.
>>>
>>> In addition to smoothing out IO performance, these changes really cut
>>> down on the amount of stack btrfs is using, which is especially
>>> important for kernels with 4k stacks enabled (fedora).
>>>
>>>   
>>>       
>> Well, no drastic changes.  On Raid, creates got better, but random write 
>> got worse. Mail server was mixed. For single disk, pretty much the same 
>> story, although CPU savings is noticeable on write, although at the 
>> expense of performance.
>>
>>     
>
> Thanks for running this, but the main performance fixes for your test
> are still in testing locally.  One thing that makes a huge difference on
> the random write run is to mount -o ssd.
>
>   
Tried a run with -o ssd on the raid system. It made some minor 
improvements in random write performance. Helps more on odirect, but 
mainly at the 16thread count. Single and 128 threads it doesn't make 
much difference.

Results syncing now to history boxacle
http://btrfs.boxacle.net/repository/raid/history/History.html

Steve

> -chris
>
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>   

Re: Btrfs experimental branch updates

[Grigory Makarevich]

Dear All,

I was wondering if the experimental branch is smth. different or it is 
the same
git://git.kernel.org/pub/scm/linux/kernel/git/mason/btrfs-unstable-standalone.git

That repository does not seem to have any branches other than head and 
master.

Thank you,
Best regards,
Grigory Makarevich

Chris Mason wrote:
> Hello everyone,
>
> I've rebased the experimental branch to include most of the
> optimizations I've been working on.
>
> The two major changes are doing all extent tree operations in delayed
> processing queues and removing many of the blocking points with btree
> locks held.
>
> In addition to smoothing out IO performance, these changes really cut
> down on the amount of stack btrfs is using, which is especially
> important for kernels with 4k stacks enabled (fedora).
>
> -chris
>
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>   

Re: Btrfs experimental branch updates

[Chris Mason]

On Sun, 2009-03-15 at 15:13 -0400, Grigory Makarevich wrote:
> Dear All,
> 
> I was wondering if the experimental branch is smth. different or it is 
> the same
> git://git.kernel.org/pub/scm/linux/kernel/git/mason/btrfs-unstable-standalone.git
> 
> That repository does not seem to have any branches other than head and 
> master.
> 

Unfortunately I still need to update the standalone tree.  All of these
changes are only in the btrfs-unstable.git tree.

-chris

Re: Btrfs experimental branch updates

[Chris Mason]

On Sun, 2009-03-15 at 09:38 -0500, Steven Pratt wrote:
> > Thanks for running this, but the main performance fixes for your test
> > are still in testing locally.  One thing that makes a huge difference on
> > the random write run is to mount -o ssd.
> >
> >   
> Tried a run with -o ssd on the raid system. It made some minor 
> improvements in random write performance. Helps more on odirect, but 
> mainly at the 16thread count. Single and 128 threads it doesn't make 
> much difference.
> 
> Results syncing now to history boxacle
> http://btrfs.boxacle.net/repository/raid/history/History.html

Well, still completely different from my test rig ;)  For the random
write run, yours runs at 580 trans/sec for btrfs and mine is going along
at 8000 trans/sec.

The part that confuses me is that you seem to have some big gaps where
just a single CPU is stuck in IO wait, and not much CPU time is in use.

Do you happen to have the blktrace logs for any of the btrfs runs?  I'd
be interested in a script that did sysrq-w every 5s and captured the
output.

-chris

Re: Btrfs experimental branch updates

[Steven Pratt]

Chris Mason wrote:
> On Sun, 2009-03-15 at 09:38 -0500, Steven Pratt wrote:
>   
>>> Thanks for running this, but the main performance fixes for your test
>>> are still in testing locally.  One thing that makes a huge difference on
>>> the random write run is to mount -o ssd.
>>>
>>>   
>>>       
>> Tried a run with -o ssd on the raid system. It made some minor 
>> improvements in random write performance. Helps more on odirect, but 
>> mainly at the 16thread count. Single and 128 threads it doesn't make 
>> much difference.
>>
>> Results syncing now to history boxacle
>> http://btrfs.boxacle.net/repository/raid/history/History.html
>>     
>
> Well, still completely different from my test rig ;)  For the random
> write run, yours runs at 580 trans/sec for btrfs and mine is going along
> at 8000 trans/sec.
>   
That is odd.  However, I think I have found 1 factor.  In rerunning with 
blktrace and sysrq an interesting thing happened.  The results got a lot 
faster.  What I did was just run the 128 thread odirect random write 
test.  Instead of 2.8MB/sec, I got 17MB/sec. Still far below the 100+ of 
ext4 and JFS, but one heck of a difference.  Here is what I think is 
going on.  We make use of a flag in FFSB to reuse the existing fileset 
if the fileset meets the setup criteria exactly.  For the test I am 
running that is 1024 100MB files.  Since all of the random write test 
are doing overwrites within the file, the file sizes do not change and 
therefore the fileset is valid for reuse.  For most Filesystems this is 
fine, but with BTRFS COW, this will result in a very different file 
layout at the start of each variation of the random write test.  The 
latest 128 thread was on a newly formatted FS. So...., I will do 2 new 
runs tonight.  First, I will re-mkfs before each random write test and 
otherwise run as usual.  Second, I plan on running the 128 threads test 
multiple times (5 minute runs each) to see if it does really degrade 
over time.  What worries me is that for the case describer above, we 
only have about 25 minutes of aging on the filesystem by the time we 
execute th last random write test, which is not a whole lot.

> The part that confuses me is that you seem to have some big gaps where
> just a single CPU is stuck in IO wait, and not much CPU time is in use.
>   
Yes, I have noticed that.

> Do you happen to have the blktrace logs for any of the btrfs runs?  I'd
> be interested in a script that did sysrq-w every 5s and captured the
> output.
>   
No, but as I mentioned above, I ran this today.  Had a bug collecting 
the sysrq, so I'll re-run tonight and post as soon as I can.

Steve


> -chris
>
>
>
>
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> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
> the body of a message to majordomo@vger.kernel.org
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>   

Re: Btrfs experimental branch updates

[Chris Mason]

On Tue, 2009-03-17 at 15:57 -0500, Steven Pratt wrote:
> Chris Mason wrote:
> > On Sun, 2009-03-15 at 09:38 -0500, Steven Pratt wrote:
> >   
> >>> Thanks for running this, but the main performance fixes for your test
> >>> are still in testing locally.  One thing that makes a huge difference on
> >>> the random write run is to mount -o ssd.
> >>>
> >>>   
> >>>       
> >> Tried a run with -o ssd on the raid system. It made some minor 
> >> improvements in random write performance. Helps more on odirect, but 
> >> mainly at the 16thread count. Single and 128 threads it doesn't make 
> >> much difference.
> >>
> >> Results syncing now to history boxacle
> >> http://btrfs.boxacle.net/repository/raid/history/History.html
> >>     
> >
> > Well, still completely different from my test rig ;)  For the random
> > write run, yours runs at 580 trans/sec for btrfs and mine is going along
> > at 8000 trans/sec.
> >   
> That is odd.  However, I think I have found 1 factor.  In rerunning with 
> blktrace and sysrq an interesting thing happened.  The results got a lot 
> faster.  What I did was just run the 128 thread odirect random write 
> test.  Instead of 2.8MB/sec, I got 17MB/sec. Still far below the 100+ of 
> ext4 and JFS, but one heck of a difference.  Here is what I think is 
> going on.  We make use of a flag in FFSB to reuse the existing fileset 
> if the fileset meets the setup criteria exactly.  For the test I am 
> running that is 1024 100MB files.  Since all of the random write test 
> are doing overwrites within the file, the file sizes do not change and 
> therefore the fileset is valid for reuse.  

Oh! In that case you're stuck waiting to cache the extents already used
in a block group.  At least I hope that's what sysrq-w will show us.
The first mods to a block group after a mount are slow while we read in
the free extents.

-chris