IS_CONSOLE stolen wholesale from Options.cpp
not sure if i should have extracted that code for DRY-ness
tested in OSX and functionality seems appropriate
unstested in a windows environment
unistd.h is for unix standard tools.
There does not appear to be a simple isatty for windows
this we only run the logic and header include in
non-windows environments
FIO would keep presenting data after an LZ4F decoding error
resulting in a NULL pointer dereference
when associated with older liblz4 version (< v1.8.1.2)
this makes it possible to specify extremely large negative compression levels,
achieving the side effect as "no compression".
It will also be possible to define larger targetlength for ultra compression mode.
There is no adverse side effect due to removing this limit.
* Replaced a non-breaking space and an en dash with a plain space and
a hyphen.
* This means the files are simple ASCII and less likely to run into
codepage issues.
- do not test level 0, as it is converted into level 3,
which feels strange when compressing multiple levels
- Use direct synchronous mode when a single worker is requested.
access negative compression levels from command line
for both compression and benchmark modes.
also : ensure proper propagation of parameters
through ZSTD_compress_generic() interface.
added relevant cli tests.
zstd bench module can focus on decompression speed _only_.
This is useful when trying to measure performance
on large input data compressed using a high level
as compression time becomes problematic (too long).
This mode is triggered by command : zstd -b -d
Problem was : in such a mode,
measured decoding speed was > 10% slower
than in nominal mode (compression + decompression),
making decompression benchmark mode much less useful.
This patch fixes the issue.
It's not completely clear why, but
moving the `memcpy()` operation sooner in the pipeline fixed it.
I can still measure some difference, but it is in the < 2% range,
so it's much more tolerable.
also : it doesn't matter anymore in which order are selected
commands `-b` and `-d`.
The combination always triggers bench_decodeOnly mode.
Silence a Coverity warning about 'windowSize' being uninitialized.
(Yes, nothing that calls this routine actually uses the windowSize
value. Still, appeasing Coverity is pretty harmless in this case.)
by invoking time() once per batch, instead of once per compression / decompression.
Batch is dynamically resized so that each round lasts approximately 1 second.
Also : increases time accuracy to nanosecond
This makes it easier to explain that nbWorkers=0 --> single-threaded mode,
while nbWorkers=1 --> asynchronous mode (one mode thread on top of the "main" caller thread).
No need for an additional asynchronous mode flag.
nbWorkers>=2 works the same as nbThreads>=2 previously.
added some test
also updated relevant doc
+ fixed a mistake in `lz4` symlink support :
lz4 utility doesn't remove source files by default (like zstd, but unlike gzip).
The symlink must behave the same.
Produces 3 statistics for ongoing frame compression :
- ingested
- consumed (effectively compressed)
- produced
Ingested can be larger than consumed due to buffering effect.
For the time being, this patch mostly fixes the % ratio issue,
since it computes consumed / produced,
instead of ingested / produced.
That being said, update is not "smooth",
because on a slow enough setting,
fileio spends most of its time waiting for a worker to complete its job.
This could be improved thanks to more granular flushing
i.e. start flushing before ongoing job is fully completed.
this happened on 32-bits build when requiring a too large input buffer,
typically on wlog=29, creating jobs of 2 GB size.
also : zstd32 now compiles with multithread support enabled by default
(can be disabled with HAVE_THREAD=0)
The compression % is no longer correct,
since it's no longer possible to make direct correlation
between nb bytes read and nb bytes written
due to large internal buffer inside CCtx
(exacerbated with --long).
The current "fix" is to no longer display the %.
A more complex solution will have to count exactly how much data has been consumed and compressed internally, within CCtx buffers.
when cli is compiled without MT support,
invoking ZSTD_p_nonBlockingMode result in an error code.
This patch only sets ZSTD_p_nonBlockingMode when ZSTD_MULTITHREAD is set, meaning there is MT support.
The error code could also be intentionnally ignored (there is no side effect).
This new parameter makes it possible to call
streaming ZSTDMT with a single thread set
which is non blocking.
It makes it possible for the main thread to do other tasks in parallel
while the worker thread does compression.
Typically, for zstd cli, it means it can do I/O stuff.
Applied within fileio.c, this patch provides non-negligible gains during compression.
Tested on my laptop, with enwik9 (1000000000 bytes) : time zstd -f enwik9
With traditional single-thread blocking mode :
real 0m9.557s
user 0m8.861s
sys 0m0.538s
With new single-worker non blocking mode :
real 0m7.938s
user 0m8.049s
sys 0m0.514s
=> 20% faster
This fixes the following crash:
$ touch exists
$ programs/zstd -r examples/ -o exists
zstd: exists already exists; not overwritten
Segmentation fault (core dumped)
* programs/fileio.c (FIO_compressMultipleFilenames):
Handle the case where we're not overwriting the destination.
Reported at https://bugzilla.redhat.com/1530049
This patch restores capability for each file to receive adapted compression parameters depending on its size.
The bug breaking this feature was relatively silly :
setting a parameter with a value "0" is supposed to be a no-op.
Unfortunately, it would pin down compression parameters as if they were manually set,
preventing later automatic adaptation.
Unfortunately, I'm currently short of a test case that could check this situation and trigger an error.
Compression parameters selection between tableID 0,1,2,3 is largely internal,
leaving no trace to outside world, not even in frame header.
The new macro might be a bit too restrictive.
Systems which do not support new test will simply default to <time.h>'s `clock_t clock()`,
suffering lesser benchmark accuracy.
Should it matter, the detection macro will have to be upgraded.
There was a flaw in the formula
which compared literal cost with match cost :
at a given position,
a non-null literal suite is going to be part of next sequence,
while if position ends a previous match, to immediately start another match,
next sequence will have a litlength of zero.
A litlength of zero has a non-null cost.
It follows that literals cost should be compared to match cost + litlength==0.
Not doing so gave a structural advantage to matches, which would be selected more often.
I believe that's what led to the creation of the strange heuristic which added a complex cost to matches.
The heuristic was actually compensating.
It was probably created through multiple trials, settling for best outcome on a given scenario (I suspect silesia.tar).
The problem with this heuristic is that it's hard to understand,
and unfortunately, any future change in the parser would impact the way it should be calculated and its effects.
The "proper" formula makes it possible to remove this heuristic.
Now, the problem is : in a head to head comparison, it's sometimes better, sometimes worse.
Note that all differences are small (< 0.01 ratio).
In general, the newer formula is better for smaller files (for example, calgary.tar and enwik7).
I suspect that's because starting statistics are pretty poor (another area of improvement).
However, for silesia.tar specifically, it's worse at level 22 (while being better at level 17, so even compression level has an impact ...).
It's a pity that zstd -22 gets worse on silesia.tar.
That being said, I like that the new code gets rid of strange variables,
which were introducing complexity for any future evolution (faster variants being in mind).
Therefore, in spite of this detrimental side effect, I tend to be in favor of it.
Fixes issue where, when `zstd --format=lz4` is fed an input larger than 128KB,
the read overruns the input buffer. This changes Zstd to use LZ4 with chained
64KB blocks. This is technically a breaking change in that some third party
LZ4 implementations may not support linked blocks. However, progress should not
be allowed to be stopped by such petty concerns as backwards compatibility!
