Testing TRIM using the yes-Method described here https://unix.stackexchange.com/a/85880/30851

hdparm.txt

# hdparm -i /dev/sda

/dev/sda:

 Model=TS256GSSD340, FwRev=SVN263, SerialNo=20140429B42802022053
 Config={ Fixed }
 RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=0
 BuffType=unknown, BuffSize=unknown, MaxMultSect=16, MultSect=16
 CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=500118192
 IORDY=on/off, tPIO={min:120,w/IORDY:120}, tDMA={min:120,rec:120}
 PIO modes:  pio0 pio3 pio4 
 DMA modes:  mdma0 mdma1 mdma2 
 UDMA modes: udma0 udma1 udma2 udma3 udma4 *udma5 
 AdvancedPM=yes: unknown setting WriteCache=enabled
 Drive conforms to: Unspecified:  ATA/ATAPI-3,4,5,6,7

 * signifies the current active mode

# hdparm -I /dev/sda

/dev/sda:

ATA device, with non-removable media
    Model Number:       TS256GSSD340                            
    Serial Number:      20140429B42802022053
    Firmware Revision:  SVN263  
    Transport:          Serial, ATA8-AST, SATA 1.0a, SATA II Extensions, SATA Rev 2.5, SATA Rev 2.6, SATA Rev 3.0
Standards:
    Supported: 9 8 7 6 5 
    Likely used: 9
Configuration:
    Logical		max	current
    cylinders	16383	16383
    heads		16	16
    sectors/track	63	63
    --
    CHS current addressable sectors:   16514064
    LBA    user addressable sectors:  268435455
    LBA48  user addressable sectors:  500118192
    Logical  Sector size:                   512 bytes
    Physical Sector size:                   512 bytes
    Logical Sector-0 offset:                  0 bytes
    device size with M = 1024*1024:      244198 MBytes
    device size with M = 1000*1000:      256060 MBytes (256 GB)
    cache/buffer size  = unknown
    Form Factor: less than 1.8 inch
    Nominal Media Rotation Rate: Solid State Device
Capabilities:
    LBA, IORDY(can be disabled)
    Queue depth: 32
    Standby timer values: spec'd by Standard, no device specific minimum
    R/W multiple sector transfer: Max = 16	Current = 16
    Advanced power management level: 254
    DMA: mdma0 mdma1 mdma2 udma0 udma1 udma2 udma3 udma4 *udma5 
         Cycle time: min=120ns recommended=120ns
    PIO: pio0 pio1 pio2 pio3 pio4 
         Cycle time: no flow control=120ns  IORDY flow control=120ns
Commands/features:
    Enabled	Supported:
       *	SMART feature set
            Security Mode feature set
       *	Power Management feature set
       *	Write cache
       *	Look-ahead
       *	Host Protected Area feature set
       *	WRITE_BUFFER command
       *	READ_BUFFER command
       *	NOP cmd
       *	DOWNLOAD_MICROCODE
       *	Advanced Power Management feature set
            SET_MAX security extension
       *	48-bit Address feature set
       *	Device Configuration Overlay feature set
       *	Mandatory FLUSH_CACHE
       *	FLUSH_CACHE_EXT
       *	SMART error logging
       *	SMART self-test
       *	General Purpose Logging feature set
       *	WRITE_{DMA|MULTIPLE}_FUA_EXT
       *	64-bit World wide name
       *	WRITE_UNCORRECTABLE_EXT command
       *	{READ,WRITE}_DMA_EXT_GPL commands
       *	Segmented DOWNLOAD_MICROCODE
       *	Gen1 signaling speed (1.5Gb/s)
       *	Gen2 signaling speed (3.0Gb/s)
       *	Gen3 signaling speed (6.0Gb/s)
       *	Native Command Queueing (NCQ)
       *	Host-initiated interface power management
       *	Phy event counters
       *	Host automatic Partial to Slumber transitions
       *	Device automatic Partial to Slumber transitions
       *	READ_LOG_DMA_EXT equivalent to READ_LOG_EXT
       *	DMA Setup Auto-Activate optimization
            Device-initiated interface power management
       *	Software settings preservation
            Device Sleep (DEVSLP)
       *	SMART Command Transport (SCT) feature set
       *	SCT Error Recovery Control (AC3)
       *	SCT Features Control (AC4)
       *	SCT Data Tables (AC5)
       *	Data Set Management TRIM supported (limit 2 blocks)
Security: 
    Master password revision code = 65534
        supported
    not	enabled
    not	locked
    not	frozen
    not	expired: security count
        supported: enhanced erase
    2min for SECURITY ERASE UNIT. 2min for ENHANCED SECURITY ERASE UNIT. 
Logical Unit WWN Device Identifier: 5000000000000000
    NAA		: 5
    IEEE OUI	: 000000
    Unique ID	: 000000000
Device Sleep:
    DEVSLP Exit Timeout (DETO): 100 ms (drive)
    Minimum DEVSLP Assertion Time (MDAT): 31 ms (drive)
Checksum: correct

smartctl.txt

# smartctl -a /dev/sda
smartctl 6.5 2016-01-24 r4214 [x86_64-linux-4.4.0-78-generic] (local build)
Copyright (C) 2002-16, Bruce Allen, Christian Franke, www.smartmontools.org

=== START OF INFORMATION SECTION ===
Model Family:     JMicron based SSDs
Device Model:     TS256GSSD340
Serial Number:    20140429B42802022053
LU WWN Device Id: 5 000000 000000000
Firmware Version: SVN263
User Capacity:    256.060.514.304 bytes [256 GB]
Sector Size:      512 bytes logical/physical
Rotation Rate:    Solid State Device
Form Factor:      < 1.8 inches
Device is:        In smartctl database [for details use: -P show]
ATA Version is:   ACS-2 (minor revision not indicated)
SATA Version is:  SATA 3.1, 6.0 Gb/s (current: 3.0 Gb/s)
Local Time is:    Fri Jun  2 12:41:41 2017 CEST
SMART support is: Available - device has SMART capability.
SMART support is: Enabled

trimtest.txt

# yes | dd iflag=fullblock bs=1M count=1 of=trim.test
1+0 records in
1+0 records out
1048576 bytes (1.0 MB, 1.0 MiB) copied, 0.0017061 s, 615 MB/s

# filefrag -s -v trim.test
Filesystem type is: ef53
File size of trim.test is 1048576 (256 blocks of 4096 bytes)
 ext:     logical_offset:        physical_offset: length:   expected: flags:
   0:        0..     255:   11044608..  11044863:    256:             last,eof
trim.test: 1 extent found

# df trim.test
Filesystem                  1K-blocks     Used Available Use% Mounted on
/dev/mapper/ubuntu--vg-root 237562536 97849388 127622576  44% /

# dd bs=4096 count=256 skip=11044608 if=/dev/mapper/ubuntu--vg-root | hexdump -C | head
256+0 records in
256+0 records out
1048576 bytes (1.0 MB, 1.0 MiB) copied, 0.0189266 s, 55.4 MB/s
00000000  79 0a 79 0a 79 0a 79 0a  79 0a 79 0a 79 0a 79 0a  |y.y.y.y.y.y.y.y.|
*
00100000

# rm trim.test
# sync
# fstrim -v .
.: 133.2 GiB (143063887872 bytes) trimmed

# echo 1 > /proc/sys/vm/drop_caches

# dd bs=4096 count=256 skip=11044608 if=/dev/mapper/ubuntu--vg-root | hexdump -C | head
256+0 records in
256+0 records out
1048576 bytes (1.0 MB, 1.0 MiB) copied, 0.00449074 s, 233 MB/s
00000000  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00100000