Re: New XFS benchmarks using David Chinner's recommendations for XFS-based optimizations.
On Fri, 4 Jan 2008, Changliang Chen wrote: Hi Justin£¬ From your report£¬It looks that the p34-default's behavior is better£¬which item make you consider that the p34-dchinner looks nice£¿ -- Best Regards The re-write and sequential input and output is faster for dchinner. Justin.
Re: New XFS benchmarks using David Chinner's recommendations for XFS-based optimizations.
Why does mdadm still use 64k for the default chunk size?
Probably because this is the best balance for average file
sizes, which are smaller than you seem to be testing with?
Well average file sizes relate less to chunk sizes than access
patterns do. Single threaded sequential reads with smaller block
sizes tend to perform better with smaller chunk sizes, for example.
File sizes do influence a bit the access patterns seen by disks.
The goals of a chunk size choice are to spread a single
''logical'' (application or filesystem level) operation over as
many arms as possible while keeping rotational latency low, to
minimize arm movement, and to minimize arm contention among
different threads.
Thus the tradeoffs influencing chunk size are about the
sequential vs. random nature of reads or writes, how many blocks
are involved in a single ''logical'' operation, and how many
threads are accessing the array.
The goal here is not to optimize the speed of the array, but the
throughput and/or latency of the applications using it.
A good idea is to consider the two extremes: a chunk size of 1
sector and a chunk size of the whole disk (or perhaps more
interestingly 1/2 disk).
For example, consider a RAID0 of 4 disks ('a', 'b', 'c', 'd')
with each chunk size of 8 sectors.
To read the first 16 chunks or 128 sectors of the array these
sector read operations ['get(device,first,last)'] have to be
issued:
00-31: get(a,0,7) get(b,0,7) get(c,0,7) get(d,0,7)
32-63: get(a,8,15) get(b,8,15) get(c,8,15) get(d,8,15)
64-95: get(a,16,23) get(b,16,23) get(c,16,23) get(d,16,23)
96-127: get(a,24,31) get(b,24,31) get(c,24,31) get(d,24,31)
I have indented the lists to show the increasing offset into
each block device.
Now, the big question here are all about the interval between
these operations, that is how large are logical operations and
how much they cluster in time and space.
For example in the above sequence it matters whether clusters of
operations involve less then 32 sectors or not, and the likely
interval between clusters generated by different concurrent
applications (consider rotational latency and likelyhood of arm
being moved between successive clusters).
So that space/time clustering depends more on how applications
process their data and how many applications concurrently access
the array, and whether they are reading or writing.
The latter point involves an exceedingly important asymmetry
that is often forgotten: an application read can only complete
when the last block is read, while a write can complete as soon
as it issued. So the time clustering of sector reads depends on
how long ''logical'' reads are as well as how long is the
interval between them.
So an application that issues frequent small reads rather than
infrequent large ones may work best with a small chunk size.
Not much related to distribution of file sizes, unless this
influences the space/time clustering of application issued
operations...
In general I like smaller chunk sizes than larger chunk sizes,
because the latter work well only in somewhat artificial cases
like simple-minded benchmarks.
In particular if one uses parity-based (not a good idea in
general...) arrays, as small chunk sizes (as well as stripe
sizes) give a better chance of reducing the frequency of RMW.
Counter to this that the Linux IO queueing subsystem (elevators
etc.) perhaps does not always take advantage of parallelizable
operations across disks as much as it could, and bandwidth
bottlenecks (e.g. PCI bus).
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Re: New XFS benchmarks using David Chinner's recommendations for XFS-based optimizations.
Peter Grandi wrote: In particular if one uses parity-based (not a good idea in general...) arrays, as small chunk sizes (as well as stripe sizes) give a better chance of reducing the frequency of RMW. Thanks for your thoughts - the above was my thinking when I posted. Regards, Richard - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: New XFS benchmarks using David Chinner's recommendations for XFS-based optimizations.
what is nobarrier ? On 12/31/07, Justin Piszcz [EMAIL PROTECTED] wrote: Dave's original e-mail: # mkfs.xfs -f -l lazy-count=1,version=2,size=128m -i attr=2 -d agcount=4 dev # mount -o logbsize=256k dev mtpt And if you don't care about filsystem corruption on power loss: # mount -o logbsize=256k,nobarrier dev mtpt Those mkfs values (except for log size) will be hte defaults in the next release of xfsprogs. Cheers, Dave. -- Dave Chinner Principal Engineer SGI Australian Software Group - I used his mkfs.xfs options verbatim but I use my own mount options: noatime,nodiratime,logbufs=8,logbsize=26214 Here are the results, the results of 3 bonnie++ averaged together for each test: http://home.comcast.net/~jpiszcz/xfs1/result.html Thanks Dave, this looks nice--the more optimizations the better! --- I also find it rather pecuilar that in some of my (other) benchmarks my RAID 5 is just as fast as RAID 0 for extracting large files (uncompressed) files: RAID 5 (1024k CHUNK) 26.95user 6.72system 0:37.89elapsed 88%CPU (0avgtext+0avgdata 0maxresident)k0inputs+0outputs (6major+526minor)pagefaults 0swaps Compare with RAID 0 for the same operation: (as with RAID5, it appears 256k-1024k..2048k possibly) is the sweet spot. Why does mdadm still use 64k for the default chunk size? And another quick question, would there be any benefit to use (if it were possible) a block size of 4096 bytes with XFS (I assume only IA64/similar arch can support it), e.g. x86_64 cannot because the page_size is 4096. [ 8265.407137] XFS: only pagesize (4096) or less will currently work. The speeds: extract speed with 4 chunk: 27.30user 10.51system 0:55.87elapsed 67%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+0outputs (6major+526minor)pagefaults 0swaps 27.39user 10.38system 0:56.98elapsed 66%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+0outputs (6major+528minor)pagefaults 0swaps 27.31user 10.56system 0:57.70elapsed 65%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+0outputs (6major+528minor)pagefaults 0swaps extract speed with 8 chunk: 27.09user 9.27system 0:54.60elapsed 66%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+0outputs (6major+525minor)pagefaults 0swaps 27.23user 8.91system 0:54.38elapsed 66%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+0outputs (6major+527minor)pagefaults 0swaps 27.19user 8.98system 0:54.68elapsed 66%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+0outputs (6major+526minor)pagefaults 0swaps extract speed with 16 chunk: 27.12user 7.24system 0:51.12elapsed 67%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+0outputs (6major+526minor)pagefaults 0swaps 27.13user 7.12system 0:50.58elapsed 67%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+0outputs (6major+528minor)pagefaults 0swaps 27.11user 7.18system 0:50.56elapsed 67%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+0outputs (6major+527minor)pagefaults 0swaps extract speed with 32 chunk: 27.15user 6.52system 0:48.06elapsed 70%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+0outputs (6major+527minor)pagefaults 0swaps 27.24user 6.38system 0:49.10elapsed 68%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+0outputs (6major+528minor)pagefaults 0swaps 27.11user 6.46system 0:47.56elapsed 70%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+0outputs (6major+528minor)pagefaults 0swaps extract speed with 64 chunk: 27.15user 5.94system 0:45.13elapsed 73%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+0outputs (6major+525minor)pagefaults 0swaps 27.17user 5.94system 0:44.82elapsed 73%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+0outputs (6major+527minor)pagefaults 0swaps 27.02user 6.12system 0:44.61elapsed 74%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+0outputs (6major+525minor)pagefaults 0swaps extract speed with 128 chunk: 26.98user 5.78system 0:40.48elapsed 80%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+0outputs (6major+525minor)pagefaults 0swaps 27.05user 5.73system 0:40.30elapsed 81%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+0outputs (6major+528minor)pagefaults 0swaps 27.11user 5.68system 0:40.59elapsed 80%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+0outputs (6major+526minor)pagefaults 0swaps extract speed with 256 chunk: 27.10user 5.60system 0:36.47elapsed 89%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+0outputs (6major+525minor)pagefaults 0swaps 27.03user 5.67system 0:36.18elapsed 90%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+0outputs (6major+528minor)pagefaults 0swaps 27.17user 5.50system 0:37.38elapsed 87%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+0outputs (6major+526minor)pagefaults 0swaps extract speed with 512 chunk: 27.06user 5.54system 0:36.58elapsed 89%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+0outputs (6major+524minor)pagefaults 0swaps 27.03user 5.59system 0:36.31elapsed 89%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+0outputs (6major+525minor)pagefaults 0swaps 27.06user 5.58system 0:36.42elapsed 89%CPU (0avgtext+0avgdata
Re: New XFS benchmarks using David Chinner's recommendations for XFS-based optimizations.
In message [EMAIL PROTECTED] you wrote: what is nobarrier ? ... # mount -o logbsize=256k,nobarrier dev mtpt See http://oss.sgi.com/projects/xfs/faq.html Q: How can I address the problem with the write cache? Best regards, Wolfgang Denk -- DENX Software Engineering GmbH, MD: Wolfgang Denk Detlev Zundel HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: [EMAIL PROTECTED] One of the advantages of being a captain is being able to ask for ad- vice without necessarily having to take it. -- Kirk, Dagger of the Mind, stardate 2715.2 - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: New XFS benchmarks using David Chinner's recommendations for XFS-based optimizations.
Justin Piszcz wrote: Why does mdadm still use 64k for the default chunk size? Probably because this is the best balance for average file sizes, which are smaller than you seem to be testing with? Regards, Richard - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
