Compression

935MB nginx log (dpx)

MB/sec in both charts means:

orig. size - compressed size
____________________________
         real time

GZ

level	cpu time	real time	size	MB/sec
1	20.4	21.4	244MB	32.29
2	20.7	21.8	236MB	32.06
3	22.7	23.7	231MB	29.70
4	27.8	28.8	215MB	25.00
5	31.0	32.0	207MB	22.75
6	36.4	37.4	202MB	19.60
7	41.0	42.2	199MB	17.44
8	44.8	45.9	198MB	16.06
9	45.3	46.4	198MB	15.88

XZ

size/time comparison is to gzip -6 (default): 202MB, 37.4 sec.

level	cpu time	real time	size	MB/sec	size savings	time cost	savings/cost
0	65.3	68.3	165M	11.27	37MB	30.9	1.20
1	64.4	66.2	129M	12.18	73MB	28.8	2.53
2	74.8	77.0	113M	10.68	89MB	39.6	2.25
3	95.8	99.4	102M	8.38	100MB	62	1.61
4	181.8	184.9	104M	4.49	98MB	147.5	0.66
5	273.8	276.9	88M	3.06	114MB	239.5	0.48
6	432.6	435.6	83M	1.96	119MB	398.2	0.30
7	460.1	467.6	77M	1.83	125MB	430.2	0.29
8	494.3	510.4	73M	1.69	129MB	473	0.27
9	535.2	544.6	70M	1.59	132MB	507.2	0.26