modules/swcore: bugfix in allocator, read new free page sooner when there are…

modules/swcore: bugfix in allocator, read new free page sooner when there are again some pages available This one fixes the situation when allocFSM in one of the input blocks requests usecount set and new allocation (S_PCKSTART_SET_AND_REQ state) while out_nomem is just before the transition from high to low. In that case arbiter grants access to this Input Block request (because setting usecount does not require out_nomem to be '0'). Then, we expect first allocation immediatelly after out_nomem is 0, but reading next page happens only when out_nomem_d1 is '0'. That's too late and the same page address was given to two subsequent allocation requests. The fix forces q_read aligned to out_nomem_d0 to read earlier next allocation address. In addition, _done_ for allocation is now generated only if there was a valid page address read in advance from the memory (to prevent double allocations of the same page).

modules/swcore: bugfix in allocator, read new free page sooner when there are…
modules/swcore: bugfix in allocator, read new free page sooner when there are again some pages available This one fixes the situation when allocFSM in one of the input blocks requests usecount set and new allocation (S_PCKSTART_SET_AND_REQ state) while out_nomem is just before the transition from high to low. In that case arbiter grants access to this Input Block request (because setting usecount does not require out_nomem to be '0'). Then, we expect first allocation immediatelly after out_nomem is 0, but reading next page happens only when out_nomem_d1 is '0'. That's too late and the same page address was given to two subsequent allocation requests. The fix forces q_read aligned to out_nomem_d0 to read earlier next allocation address. In addition, _done_ for allocation is now generated only if there was a valid page address read in advance from the memory (to prevent double allocations of the same page).
b1ff9b89 · Grzegorz Daniluk · 29aef651 · b1ff9b89
Commit b1ff9b89 authored Apr 27, 2015 by Grzegorz Daniluk
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Showing with 6 additions and 4 deletions

swc_page_alloc_ram_bug.vhd ...swcore/optimized_new_allocator/swc_page_alloc_ram_bug.vhd +6 -4

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--- a/modules/wrsw_swcore/optimized_new_allocator/swc_page_alloc_ram_bug.vhd
+++ b/modules/wrsw_swcore/optimized_new_allocator/swc_page_alloc_ram_bug.vhd
@@ -339,10 +339,12 @@ begin  -- syn
  process(clk_i)
  begin
    if rising_edge(clk_i) then
-      if (rst_n_i = '0' or alloc_req_in.alloc = '1') then
+      if (rst_n_i = '0') then
        pg_adv_valid <= '0';
-      elsif(out_nomem_d1 = '0') then
+      elsif(out_nomem_d0 = '0') then
        pg_adv_valid <= '1';
+      elsif(alloc_req_in.alloc = '1') then
+        pg_adv_valid <= '0';
      end if;
    end if;
  end process;
@@ -363,7 +365,7 @@ begin  -- syn
  -- nomem_d0  : _______|-------
  -- alloc_d0  " _______|-|____  <= this need to be handled
  -- nomem_d1  : ________|-------
-  q_read_p0 <= '1' when (pg_adv_valid = '0' and out_nomem_d1 = '0') else '0';
+  q_read_p0 <= '1' when ((pg_adv_valid = '0' or alloc_req_d0.alloc='1') and out_nomem_d0 = '0') else '0';
  
  -- address of page stored in the memory (queue)
  q_input_addr_p1 <= std_logic_vector(wr_ptr_p1) when initializing = '1' else alloc_req_d1.pgaddr_free;
@@ -517,7 +519,7 @@ begin  -- syn
      if (rst_n_i = '0') or (initializing = '1') then
        done_p1 <= '0';
      else
-        if(((alloc_req_d0.alloc      = '1'  and out_nomem_d1      = '0') or 
+        if(((alloc_req_d0.alloc      = '1'  and pg_adv_valid      = '1') or 
             alloc_req_d0.set_usecnt = '1'  or  alloc_req_d0.free = '1'  or 
             alloc_req_d0.f_free     = '1') and initializing      = '0') then
          done_p1 <= '1';