RE: Bluestore different allocator performance Vs FileStore

[Ramesh Chander <Ramesh.Chander@sandisk.com>]

I think insert_free is limited by speed of function clear_bits here.

Though set_bits and clear_bits have same logic except one sets and another clears. Both of these does 64 bits (bitmap size) at a time.

I am not sure if doing memset will make it faster. But if we can do it for group of bitmaps, then it might help.

I am looking in to code if we can handle mkfs and osd mount in special way to make it faster.

If I don't find an easy fix, we can go to path of deferring init to later stage as and when required.

-Ramesh

> -----Original Message-----
> From: ceph-devel-owner@vger.kernel.org [mailto:ceph-devel-
> owner@vger.kernel.org] On Behalf Of Allen Samuels
> Sent: Thursday, August 11, 2016 4:28 AM
> To: Sage Weil; Somnath Roy
> Cc: ceph-devel
> Subject: RE: Bluestore different allocator performance Vs FileStore
>
> We always knew that startup time for bitmap stuff would be somewhat
> longer. Still, the existing implementation can be speeded up significantly. The
> code in BitMapZone::set_blocks_used isn't very optimized. Converting it to
> use memset for all but the first/last bytes should significantly speed it up.
>
>
> Allen Samuels
> SanDisk |a Western Digital brand
> 2880 Junction Avenue, San Jose, CA 95134
> T: +1 408 801 7030| M: +1 408 780 6416
> allen.samuels@SanDisk.com
>
>
> > -----Original Message-----
> > From: ceph-devel-owner@vger.kernel.org [mailto:ceph-devel-
> > owner@vger.kernel.org] On Behalf Of Sage Weil
> > Sent: Wednesday, August 10, 2016 3:44 PM
> > To: Somnath Roy <Somnath.Roy@sandisk.com>
> > Cc: ceph-devel <ceph-devel@vger.kernel.org>
> > Subject: RE: Bluestore different allocator performance Vs FileStore
> >
> > On Wed, 10 Aug 2016, Somnath Roy wrote:
> > > << inline with [Somnath]
> > >
> > > -----Original Message-----
> > > From: Sage Weil [mailto:sage@newdream.net]
> > > Sent: Wednesday, August 10, 2016 2:31 PM
> > > To: Somnath Roy
> > > Cc: ceph-devel
> > > Subject: Re: Bluestore different allocator performance Vs FileStore
> > >
> > > On Wed, 10 Aug 2016, Somnath Roy wrote:
> > > > Hi, I spent some time on evaluating different Bluestore allocator
> > > > and freelist performance. Also, tried to gaze the performance
> > > > difference of Bluestore and filestore on the similar setup.
> > > >
> > > > Setup:
> > > > --------
> > > >
> > > > 16 OSDs (8TB Flash) across 2 OSD nodes
> > > >
> > > > Single pool and single rbd image of 4TB. 2X replication.
> > > >
> > > > Disabled the exclusive lock feature so that I can run multiple
> > > > write  jobs in
> > parallel.
> > > > rbd_cache is disabled in the client side.
> > > > Each test ran for 15 mins.
> > > >
> > > > Result :
> > > > ---------
> > > >
> > > > Here is the detailed report on this.
> > > >
> > > >
> >
> https://github.com/somnathr/ceph/blob/6e03a5a41fe2c9b213a610200b2e8a
> > > > 25 0cb05986/Bluestore_allocator_comp.xlsx
> > > >
> > > > Each profile I named based on <allocator>-<freelist> , so in the
> > > > graph for
> > example "stupid-extent" meaning stupid allocator and extent freelist.
> > > >
> > > > I ran the test for each of the profile in the following order
> > > > after creating a
> > fresh rbd image for all the Bluestore test.
> > > >
> > > > 1. 4K RW for 15 min with 16QD and 10 jobs.
> > > >
> > > > 2. 16K RW for 15 min with 16QD and 10 jobs.
> > > >
> > > > 3. 64K RW for 15 min with 16QD and 10 jobs.
> > > >
> > > > 4. 256K RW for 15 min with 16QD and 10 jobs.
> > > >
> > > > The above are non-preconditioned case i.e ran before filling up
> > > > the entire
> > image. The reason is I don't see any reason of filling up the rbd
> > image before like filestore case where it will give stable performance
> > if we fill up the rbd images first. Filling up rbd images in case of
> > filestore will create the files in the filesystem.
> > > >
> > > > 5. Next, I did precondition the 4TB image with 1M seq write. This
> > > > is
> > primarily because I want to load BlueStore with more data.
> > > >
> > > > 6. Ran 4K RW test again (this is called out preconditioned in the
> > > > profile) for 15 min
> > > >
> > > > 7. Ran 4K Seq test for similar QD for 15 min
> > > >
> > > > 8. Ran 16K RW test again for 15min
> > > >
> > > > For filestore test, I ran tests after preconditioning the entire image first.
> > > >
> > > > Each sheet on the xls have different block size result , I often
> > > > miss to navigate through the xls sheets , so, thought of
> > > > mentioning here
> > > > :-)
> > > >
> > > > I have also captured the mkfs time , OSD startup time and the
> > > > memory
> > usage after the entire run.
> > > >
> > > > Observation:
> > > > ---------------
> > > >
> > > > 1. First of all, in case of bitmap allocator mkfs time (and thus
> > > > cluster
> > creation time for 16 OSDs) are ~16X slower than stupid allocator and
> filestore.
> > Each OSD creation is taking ~2min or so sometimes and I nailed down
> > the
> > insert_free() function call (marked ****) in the Bitmap allocator is
> > causing that.
> > > >
> > > > 2016-08-05 16:12:40.587148 7f4024d258c0 10 freelist enumerate_next
> > > > start
> > > > 2016-08-05 16:12:40.975539 7f4024d258c0 10 freelist enumerate_next
> > > > 0x4663d00000~69959451000
> > > > 2016-08-05 16:12:40.975555 7f4024d258c0 10
> > > > bitmapalloc:init_add_free instance 139913322803328 offset
> > > > 0x4663d00000 length 0x69959451000
> > > > ****2016-08-05 16:12:40.975557 7f4024d258c0 20
> > > > bitmapalloc:insert_free instance 139913322803328 off 0x4663d00000
> > > > len 0x69959451000****
> > > > ****2016-08-05 16:13:20.748934 7f4024d258c0 10 freelist
> > > > enumerate_next
> > > > end****
> > > > 2016-08-05 16:13:20.748978 7f4024d258c0 10
> > > > bluestore(/var/lib/ceph/osd/ceph-0) _open_alloc loaded 6757 G in 1
> > > > extents
> > > >
> > > > 2016-08-05 16:13:23.438511 7f4024d258c0 20 bluefs _read_random
> > > > read buffered 0x4a14eb~265 of ^A:5242880+5242880
> > > > 2016-08-05 16:13:23.438587 7f4024d258c0 20 bluefs _read_random got
> > > > 613
> > > > 2016-08-05 16:13:23.438658 7f4024d258c0 10 freelist enumerate_next
> > > > 0x4663d00000~69959451000
> > > > 2016-08-05 16:13:23.438664 7f4024d258c0 10
> > > > bitmapalloc:init_add_free instance 139913306273920 offset
> > > > 0x4663d00000 length 0x69959451000
> > > > *****2016-08-05 16:13:23.438666 7f4024d258c0 20
> > > > bitmapalloc:insert_free instance 139913306273920 off 0x4663d00000
> > > > len
> > > > 0x69959451000*****
> > > > *****2016-08-05 16:14:03.132914 7f4024d258c0 10 freelist
> > > > enumerate_next end
> > >
> > > I'm not sure there's any easy fix for this. We can amortize it by
> > > feeding
> > space to bluefs slowly (so that we don't have to do all the inserts at
> > once), but I'm not sure that's really better.
> > >
> > > [Somnath] I don't know that part of the code, so, may be a dumb
> question.
> > This is during mkfs() time , so, can't we say to bluefs entire space
> > is free ? I can understand for osd mount and all other cases we need
> > to feed the free space every time.
> > > IMO this is critical to fix as cluster creation time will be number
> > > of OSDs * 2
> > min otherwise. For me creating 16 OSDs cluster is taking ~32min
> > compare to
> > ~2 min for stupid allocator/filestore.
> > > BTW, my drive data partition is ~6.9TB , db partition is ~100G and
> > > WAL is
> > ~1G. I guess the time taking is dependent on data partition size as well (?
> >
> > Well, we're fundamentally limited by the fact that it's a bitmap, and
> > a big chunk of space is "allocated" to bluefs and needs to have 1's set.
> >
> > sage
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