Issues for Android about replacing zlib using zstd

[296777513]

Hi
I am attempting to port zstd to Android libziparchive module, by using zlibWrapper to replace zlib .
As scenes in Androd concerns more about decompress speed, so I test decompressing zip files(like bmp.zip(bmp file compressed by zstd/zlib firstly) and apk) using zlib/zstd.
The data below shows gaining little benefit comparing zlib, do you have any advise for my occuration?
thanks

test steps:
1: firstly, compress bmp/txt files into test_zstd.zip using zstd, test_zlib.zip using zlib;
2: secondly, decompress zip files above into memory or file system;
3: calculating time consuming for step 2.

[jinguang-dong]

Hi Cyan4973，

Please help to analysis and give some suggestion  for the decompress benfit issue.

[terrelln]

It seems the decompressor is running at about 100 MB/s in your tests.

zstd so far is primarily optimized for x86, so it is expected to be slower on ARM, but that is too slow. I ran the following program on my iPhone 6s and looked at the logging output.

#import "bench.h"

/* ... */

- (void)viewDidLoad {
    ZSTD_compressionParameters params;
    memset(&params, 0, sizeof(params));
    BMK_SetNbSeconds(5);
    BMK_setNotificationLevel(1);
    BMK_setDecodeOnly(0);
    BMK_benchFiles(NULL, 0, NULL, 1, 10, &params);
}
/* ... */

When running on an unoptimized build it decompressed at about 100 MB/s. When running a build optimized with -Os it decompressed at about 800 MB/s. For reference, Apple's zlib implementation decompresses at about 270 MB/s. I know it isn't Android, but I would expect similar relative results on the same architecture.

Is your binary compiled with optimizations?

[jinguang-dong]

Hi Terrelln,
Thanks for your propose and We will try it.

[powof2]

May be it is something about your android system? 64-bits is way faster.
here is another test.

[Cyan4973]

Both advises by @terrelln and @powof2 are relevant :

• Check compiler optimisation settings
• Check if your test system is 32 or 64 bits. It makes a substantial difference.

[296777513]

Hi Cyan4973 and terrelln,
Thanks for your reply, we run a build optimized with -O2 default, and test in 64-bits case.
I see that the file tested may influence the decompress speed, use fullbench and turbobench, 800+M/s when decompressing default 10M sample, while only 450+M/s when decompressing bmp file. Both tested in my linux server.

Also, for the same test file(10M sample), linux server runs decompressing in 800+M, while my Android 7.0 mobile phone only runs in 450+M(data shows below).

So, I think both the test files and my Android platform cause the decomressing speed too slow.

Thanks