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1 Introduction:
3 The Flexible Filesystem Benchmark (FFSB) is a filesystem performance
4 measurement tool. It is a multi-threaded application (using
5 pthreads), written entirely in C with cross-platform portability in
6 mind. It differs from other filesystem benchmarks in that the user
7 may supply a profile to create custom workloads, while most other
8 filesystem benchmarks use a fixed set of workloads.
10 As of version 5.1, it supports seven different basic operations, support
11 for multiple groups of threads with different operation mixtures,
12 support for operation across multiple filesystems, and support for
13 filesystem aging prior to benchmarking.
16 Differences from version 4.0 and older:
18 Version 5.0 and above represent almost a total re-write and many
19 things have changed. In version 5.0 and above FFSB moved to a
20 time-regulated run versus doing a set number of different operations
21 and timing the whole thing. This is primarily to better deal with the
22 use of multiple threadgroups which would otherwise not be synchronized
23 at termination time.
25 Additionally, the FFSB configuration file format has changed in
26 version 5.0, although we do support old-style configuration files
27 along with a run-time passed on the command line. In this mode,
28 version 5.0 and above ignores the iterations parameter, and simply
29 uses the time specified on the command line.
31 Behaviorally, most of the old operations are the same -- sequential
32 reads and sequential writes work as they did before. One change in
33 version 5.0 is the skip-read behavior of reading then seeking forward
34 a fixed amount then reading again is removed, we now support fully
35 randomized reads and writes from random offsets within the file.
37 Version 4.0 didn't support overwrites (only appends) so we interpret
38 writes in old config files to be append operations.
40 On Linux, CPU utilization information will only be accurate for
41 systems using NPTL, older Linuxthreads systems will probably only see
42 zeros for CPU utilization because Linuxthreads is non-compliant to
43 POSIX. Version 4.0 and older could be recompiled to work on
44 Linuxthreads, but in 5.0 and later we no longer support this.
46 We no longer support the "outputfile" on the command line.
48 One should simply use tee or similar to capture the output. FFSB
49 unbuffers standard out for this purpose, and errors are sent on
50 standard error.
52 Global options:
54 There are eight valid global options placed at the beginning of the
55 profile. Three of them are required: num_filesystems (number of
56 filesystems), num_threadgroups (number of threadgroups), and time
57 (running time of the benchmark). The other five options are:
59 directio - each call to open will be made using O_DIRECT
60 alignio - aligns all block operations for random reads and writes
61 on 4k boundaries.
62 bufferedio - currently ignorred: it is intended to use libc
63 fread,rwrite, instead of just unix read and write calls
64 verbose - currently ignored
66 callout - calls and external command and waits for its termination
67 before FFSB begins the benchmark phase.
68 This is useful for synchronizing distributed clients,
69 starting profilers, etc.
71 They must be specified in the above order (num_filesystems,
72 num_threadgroups, time, directio, alignio, bufferedio, verbose,
73 callout).
77 Filesystems:
79 Filesystems are specified to FFSB in the form of a directory. FFSB
80 assumes that the filesystem is mounted at this directory and will not
81 do any verification of this fact beyond ensuring it can read/write to
82 the location. So be careful to ensure something with enough space to
83 handle the dataset is in fact mounted at the specified location.
85 In the filesystem clause of the profile, one may set the starting
86 number of files and directories as well as a minimum and maximum
87 filesize for the filesystem. One may also specify the blocksize
88 used for creating the files separately in the filesystem clause.
90 Also, if a filesystem is to be aged, a special threadgroup clause may
91 be embedded in a filesystem clause to specify the operation mixture
92 and number of threads used to age the filesystem. This threadgroup is
93 run until filesystem utilization reaches the specified amount.
95 Inheritance -- if you are using multiple filesystems, all attributes
96 except the location should be inherited from the previous filesystem.
97 This is done to make it easier to add groups of similar filesystems.
98 In this case, only the location is required in the filesystem clause.
100 As of version 5.1, filesystem re-use is supported if a given
101 filesystem hasn't been modified beyond it's orginal specifications
102 (number of files and directories is correct, and file sizes are within
103 specifications). This can be a huge time saver if one wishes to do
104 multiple runs on the same data-set without altering it during a run,
105 because the fileset doesn't need to be recreated before each run.
107 To do this, specify "reuse=1" in the filesystem clause, and FFSB will
108 verify the fileset first, and if it checks out it will use it.
109 Otherwise, it will remove everything and re-create the filesets for
110 that filesystem.
112 Threadgroups:
114 An arbitrary number of threadgroups with differing numbers of threads
115 and operation mixes can be specified. The operations are specified
116 using a weighting for each operation, if an operation isn't specified
117 it's weighting is assumed to be zero (not used).
119 "Think-time" for a threadgroup may also be specified in millisecond
120 amounts using the "op_delay" parameter, where every thread will wait
121 for the specified amount between each operation.
123 Operations:
125 All operations begin by randomly selecting a filesystem from the list
126 of filesystems specified in the profile. The distribution aims to be
127 uniform across all filesystems.
130 The seven operations are:
132 reads - read() calls with an overall amount and a blocksize
133 operates on existing files. Care must be taken to ensure
134 that the read amount is smaller than the size of any possible
135 file.
137 If random_read is specified, then the each individual blocks
138 will be read starting from a random point with the file, and
139 this will continune until the entire amount specifed has been
140 read. This offset of each random block will be totally
141 random to the byte level, unless the "alignio" global parameter
142 is on, and then the reads will be 4096 byte aligned. This is
143 generally recommended.
146 readall - Very similar to read above, except it doesn't take an
147 amount; it simply reads the entire file sequentially using the
148 read_blocksize. This is useful for situations where
149 different filesystems have differently sized files, and sequential
150 read patterns across all filesystems are desired.
152 writes - write() calls with an overall amount and blocksize
153 this is an overwrite operation and will not enlarge an existing
154 file, again one must be careful not to specify a write amount
155 that is larger than any possible file in the data set.
157 If random_write is specified, then the each individual blocks
158 will be written starting from a random point with the file, and
159 this will continune until the entire amount specifed has been
160 written out. This offset of each random block will be totally
161 random to the byte level, unless the "alignio" global parameter
162 is on, and then the writes will be 4096 byte aligned. This
163 is generally recommended.
165 If the fsync_flag parameter for the threadgroup is non-zero,
166 then after all of the write calls are finished, fsync() will
167 be called on the file descriptor before the file is closed.
170 creates - creates a file using open() call and determines the size
171 randomly between on the constraints (min_filesize and
172 max_filesize) for the selected filesystem. Write operations will
173 be done using the same blocksize as is specified for the
174 write operation.
175 deletes - calls unlink() on a filename and removes it from the
176 internal data-structures. One must be careful to ensure
177 there are enough files to delete at all times or else the benchmark
178 will terminate.
179 appends - calls write() using the append flag with an overall amount
180 and a blocksize to be appended onto a randomly chosen file.
181 metas - this is actually a mix of several different directory
182 operations. Each "meta" operation consists of two directory
183 creates, one directory remove, and a directory rename.
184 These operations are all carried out separately from the
185 other 5 operations.
187 Operation accounting:
189 Each operation which uses a blocksize counts each read/write of a
190 blocksize as an operation (reads,writes,creates, and appends) whereas
191 deletes and metas are considered single operations.
193 Running the benchmark:
195 There are three phases to running the benchmark, aging, fileset
196 creates, and the benchmark phase.
198 The create phase is carried out across all filesystems simultanously
199 with one dedicated thread per filesystem.
201 After the create phase, sync() is called to ensure all dirty data gets
202 written out before the benchmark phase begins, and sync() is again
203 called at the end of the benchmark phase. The time in sync() at the
204 end of the benchmark phase is counted as part of the benchmark phase.
206 Caveats/Holes/Bugs:
208 Aging and aging across multiple filesystems simultaneously hasn't been tested
209 very much.
211 If *any* i/o operation or system call/libc call fails, the benchmark
212 will terminate immediately.
214 The parser doesn't handle mal-formed or incorrect profiles very well
215 (or at all).
217 The parser doesn't check to make sure all of the appropriate options
218 have been specified. For example, if writes are specified in a
219 threadgroup but write_blocksize isn't specified, the parse won't catch
220 it, but the benchmark run will fail later on.
223 Configuration Files (new style):
225 New Style Configuration allows for arbitrary newlines between lines,
226 and comments using '#' at the start of a line. Also it allows tabs,
227 whitespace before and after configuration parameters.
229 The new style configuration file is broken up into three main parts:
231 global parameters, filesystems, and threadgroups
233 The sections must be in the above order.
235 Global parameters:
237 Global Paramters are described above, the first three are always
238 required. Example:
240 ----------
242 num_filesystems=1
243 num_threadgroups=1
244 time=30 # time is in seconds
246 directio=0 # don't use direct io
247 alignio=1 # align random IOs to 4k
248 bufferedio=0 # this does nothing right now
249 verbose=0 # this does nothing right now
251 # calls and external command and waits
252 # everything until the newline is taken
253 # so you can have abritrary parmeters
254 callout=synchronize.sh myhostname
256 ---------
258 All of these must appear in this order, though you can leave out the
259 optional ones.
261 Filesystems:
263 Filesystems describe differnt logical sets of files residing in
264 different directorys. There is no strict requirement that they
265 actually be on different filesystems, only that the directory
266 specified already exists.
268 Filesystems are specified by a clause with a filesystem number like
269 this:
271 [filesystem0]
272 location=/mnt/testing/
273 num_files=10
274 num_dirs=1
275 max_filesize=4096
276 min_filesize=4096
277 [end0]
280 The clause must always begin with [filesystemX] and end with [endX]
281 where X is the number of that filesystem.
283 You should start wiht X = 0, and increment by one for each following
284 filesystem. If they are out of order, things will likely break.
286 The required information for each filesystem is: location, num_files,
287 num_dirs, max_filesize, and min_filesize. Beyond those the following
288 four options are supported:
292 reuse=1 # check the filesystem to see if it is reusable
294 # filesystem aging, three components required
295 # takes agefs=1 to turn it on
296 # then a valid threadgroup specification
297 # then a desired utilization percentage
299 agefs=1 # age the filesystem according to the following threadgroup
300 [threadgroup0]
301 num_threads=10
302 write_size=40960
303 write_blocksize=4096
304 create_weight=10
305 append_weight=10
306 delete_weight=1
307 [end0]
308 desired_util=0.20 # In this case, age until the fs is 20% full
310 create_blocksize=4096 # specify the blocksize to write()
311 # for creating the fileset, defaults to 4096
313 age_blocksize=4096 # specify the blocksize to write() for aging
316 Also, to allow lazy people to use lots of filesystems, we support
317 filesystem inheritance, which simply copies all options but the
318 location from the previous filesystem clause if nothing is specified.
319 Obviously, this doesn't work for filesystem0. (May not work for aging
320 either?)
322 Full blown filesystem clause example:
324 ----
326 [filesystem0]
328 # required parts
330 location=/home/sonny/tmp
331 num_files=100
332 num_dirs=100
333 max_filesize=65536
334 min_filesize=4096
336 # aging part
337 agefs=0
338 [threadgroup0]
339 num_threads=10
340 write_size=40960
341 write_blocksize=4096
342 create_weight=10
343 append_weight=10
344 delete_weight=1
345 [end0]
346 desired_util=0.02 # age until 2% full
348 # other optional commands
350 create_blocksize=1024 # use a small create blocksize
351 age_blocksize=1024 # and smaller age create blocksize
352 reuse=0 # don't reuse it
353 [end0]
357 --
359 Threadgroups:
361 Threadgropus are very similar to filesystems in that any number of
362 them can be specified in clauses, and they must be in order starting
363 with threadgroup0.
365 Example:
367 ---
369 [threadgroup0]
370 num_threads=32
371 read_weight=4
372 append_weight=1
374 write_size=4096
375 write_blocksize=4096
377 read_size=4096
378 read_blocksize=4096
379 [end0]
381 ---
383 In a threadgroup clause, num_threads is required and must be at least
384 1. Then, at least one operation must be given a weight greater than 0
385 to be a valid threadgroup. Operations can be given a weighting of 0,
386 and in this case they are ignored.
388 Certain operations will also require other commands, for example, if
389 read_weight is greater than zero, then one must also include a
390 read_size and a read_blocksize. Here's the table of requirements and
391 options:
394 Operation Requirements Options
395 -- -- --
396 read_weight read_size, read_blocksize read_random
397 readall_weight read_blocksize none
398 write_weight write_size, write_blocksize write_random,fsync_file
399 create_weight write_blocksize or create_blocksize none
400 append_weight write_blocksize, write_size none
401 delete_weight none none
402 meta_weight none none
406 Other threadgroup options:
408 op_delay=10 # specify a wait between operations in milli-seconds
410 bindfs=3 # This allows you to restrict a threadgroup's operation
411 # to a specific filesystem number. Currently only
412 # binding to one specific filesystem is supported