Split TLBs

By: matthew (willy.delete@this.infradead.org), August 7, 2021 10:21 am
Room: Moderated Discussions
Intel seem to have changed how their TLBs work recently. My i7-1165G7 reports:

TLB info
L1 Instruction TLB: 4KB pages, 8-way associative, 128 entries
L1 Instruction TLB: 4MB/2MB pages, 8-way associative, 16 entries
L1 Store Only TLB: 1GB/4MB/2MB/4KB pages, fully associative, 16 entries
L1 Load Only TLB: 4KB pages, 4-way associative, 64 entries
L1 Load Only TLB: 4MB/2MB pages, 4-way associative, 32 entries
L1 Load Only TLB: 1GB pages, fully associative, 8 entries
L2 Unified TLB: 4MB/2MB/4KB pages, 8-way associative, 1024 entries

From the Intel SDM:

00001b: Data TLB.
00010b: Instruction TLB.
00011b: Unified TLB*.
00100b: Load Only TLB. Hit on loads; fills on both loads and stores.
00101b: Store Only TLB. Hit on stores; fill on stores.
* Some unified TLBs will allow a single TLB entry to satisfy data read/write and instruction fetches. Others will require separate entries (e.g., one loaded on data read/write and another loaded on an instruction fetch)

Why split the Data TLB into Load-only and Store-only? Is it a way to increase the number of TLB entries without paying the full cost of increasing the number of entries? Is there a speed advantage to having a TLB that is only hit on stores? Or is there something else going on?

(I'm a software person; I have no experience in hardware design)
 Next Post in Thread >
TopicPosted ByDate
Split TLBsmatthew2021/08/07 10:21 AM
  Split TLBsanon2021/08/07 11:12 AM
  Split TLBsMark Roulo2021/08/07 04:16 PM
  Split TLBsanon22021/08/07 09:13 PM
  Performance and power!!David Kanter2021/08/09 10:35 AM
    Performance and power!!anon2021/08/10 01:31 AM
      Performance and power!!rwessel2021/08/10 05:43 AM
        Performance and power!!Michael S2021/08/10 07:40 AM
          Performance and power!!Mark Roulo2021/08/10 07:46 AM
            Performance and power!!Michael S2021/08/11 01:33 AM
              Performance and power!!rwessel2021/08/11 04:44 AM
                Performance and power!!Michael S2021/08/11 05:22 AM
                  Performance and power!!rwessel2021/08/11 06:17 AM
              FPGA SRAM blocksUngo2021/08/12 11:50 AM
      Performance and power!!David Kanter2021/08/10 10:31 AM
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