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powerpc/kexec: Speedup kexec hash PTE tear down
Currently for kexec the PTE tear down on 1TB segment systems normally requires 3 hcalls for each PTE removal. On a machine with 32GB of memory it can take around a minute to remove all the PTEs. This optimises the path so that we only remove PTEs that are valid. It also uses the read 4 PTEs at once HCALL. For the common case where a PTEs is invalid in a 1TB segment, this turns the 3 HCALLs per PTE down to 1 HCALL per 4 PTEs. This gives an > 10x speedup in kexec times on PHYP, taking a 32GB machine from around 1 minute down to a few seconds. Signed-off-by: Michael Neuling <mikey@neuling.org> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
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@ -367,21 +367,28 @@ static void pSeries_lpar_hptab_clear(void)
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{
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unsigned long size_bytes = 1UL << ppc64_pft_size;
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unsigned long hpte_count = size_bytes >> 4;
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unsigned long dummy1, dummy2, dword0;
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struct {
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unsigned long pteh;
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unsigned long ptel;
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} ptes[4];
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long lpar_rc;
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int i;
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int i, j;
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/* TODO: Use bulk call */
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for (i = 0; i < hpte_count; i++) {
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/* dont remove HPTEs with VRMA mappings */
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lpar_rc = plpar_pte_remove_raw(H_ANDCOND, i, HPTE_V_1TB_SEG,
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&dummy1, &dummy2);
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if (lpar_rc == H_NOT_FOUND) {
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lpar_rc = plpar_pte_read_raw(0, i, &dword0, &dummy1);
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if (!lpar_rc && ((dword0 & HPTE_V_VRMA_MASK)
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!= HPTE_V_VRMA_MASK))
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/* Can be hpte for 1TB Seg. So remove it */
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plpar_pte_remove_raw(0, i, 0, &dummy1, &dummy2);
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/* Read in batches of 4,
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* invalidate only valid entries not in the VRMA
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* hpte_count will be a multiple of 4
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*/
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for (i = 0; i < hpte_count; i += 4) {
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lpar_rc = plpar_pte_read_4_raw(0, i, (void *)ptes);
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if (lpar_rc != H_SUCCESS)
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continue;
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for (j = 0; j < 4; j++){
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if ((ptes[j].pteh & HPTE_V_VRMA_MASK) ==
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HPTE_V_VRMA_MASK)
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continue;
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if (ptes[j].pteh & HPTE_V_VALID)
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plpar_pte_remove_raw(0, i + j, 0,
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&(ptes[j].pteh), &(ptes[j].ptel));
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}
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}
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}
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