Scheme to improve efficiency of garbage collection in cached flash translation layer

A method comprising:

• managing a NAND memory device, the NAND memory device having a memory array of memory cells arranged as a number of blocks of memory cells, each block having a number of pages;
• updating a count of valid pages of a block of the number of blocks upon writing to a logical address for the memory array in which the logical address is associated with the block, the count updated in a first counter table corresponding to a logical to physical mapping table stored in a region in the NAND memory device and corresponding to the block;
• resetting a bit in a second table in response to the updating of the count for the block in the first counter table being a decrement to zero, identifying zero valid pages in the block, the bit in the second table corresponding to the count in the first counter table, the second table having a bit for each count in the first table;
• and
• performing a garbage collection procedure for the NAND memory device using the bit reset and other bits in the second table.

A method comprising:

• choosing a source block of a NAND memory device for garbage collection in response to a triggering of a garbage collection procedure in the NAND memory device, the NAND memory device arranged as a number of blocks, each block having a number of pages;
• accessing a region validity bitmap table corresponding to the source block, the region validity bitmap table structured as a table corresponding to logical to physical mapping tables, each logical to physical mapping table stored in a region of multiple regions in the NAND memory device, the region validity bitmap table, in conjunction with a region validity counter table having counts of valid pages for each block of the region, maintaining an indication of whether each logical to physical mapping table is involved in the garbage collection such that a bit in the region validity bitmap table for a block in the region is reset in response to decrementing a count to zero in the region validity counter table for the block in the region, identifying zero valid pages in the block in the region, the region validity bitmap table having a bit for each count in the region validity counter table;
• identifying a logical to physical mapping table indicated by the region validity bitmap table as having one or more entries associated with one or more valid pages;
• loading the identified logical to physical mapping table into a random access memory;
• searching the identified logical to physical mapping table in the random access memory for a valid page;
• and
• loading the valid page into a destination block, the destination block being different from the source block.

A system comprising:

• a host processor;
• a NAND memory device communicatively coupled with the host processor, the NAND memory device having an array of memory cells arranged as a number of blocks of memory, each block having a number of pages;
• and
• firmware including a flash translation layer structured to operate with a logical to physical mapping table, the logical to physical mapping table saved in the NAND memory device and split into logical to physical mapping table regions, each logical to physical mapping table region associated with a set of counters, the number of counters of each set equal to the number of blocks of the NAND device associated with the respective logical to physical mapping table region, and the flash translation layer structured to operate with a second table that contains a bit for each counter of each logical to physical mapping table region, the firmware including instructions, when executed by a controller, that enable operations, the operations including:
• an increment or a decrement of a counter of the set of counters associated with a block of the number of blocks upon writing data to the array in which the data is associated with the block;
• and
• a setting of a bit in the second table in response to and corresponding to the incremented or decremented counter and the block, based on a status of the writing of the data, including resetting the bit in the second table in response to the counter for the block being decremented to zero, identifying zero valid pages in the block, the bit in the second table corresponding to the counter for the block of the one region, the second table having a bit for each counter.