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pseries: Add helper to calculate recommended hash page table size 

At present we calculate the recommended hash page table (HPT) size for a
pseries guest just once in ppc_spapr_init() before allocating the HPT.
In future patches we're going to want this calculation in other places, so
this splits it out into a helper function.  While we're at it, change the
calculation to use ctz() instead of an explicit loop.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>
This commit is contained in:
David Gibson 2016-02-09 10:15:12 +10:00
parent 715c54071a
commit 8dfe8e7f4f
1 changed files with 14 additions and 10 deletions
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24
hw/ppc/spapr.c
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@ -1050,6 +1050,19 @@ static void close_htab_fd(sPAPRMachineState *spapr)
spapr->htab_fd = -1; spapr->htab_fd = -1;
} }
static int spapr_hpt_shift_for_ramsize(uint64_t ramsize)
{
int shift;
/* We aim for a hash table of size 1/128 the size of RAM (rounded
* up). The PAPR recommendation is actually 1/64 of RAM size, but
* that's much more than is needed for Linux guests */
shift = ctz64(pow2ceil(ramsize)) - 7;
shift = MAX(shift, 18); /* Minimum architected size */
shift = MIN(shift, 46); /* Maximum architected size */
return shift;
}
static void spapr_alloc_htab(sPAPRMachineState *spapr) static void spapr_alloc_htab(sPAPRMachineState *spapr)
{ {
long shift; long shift;
@ -1790,16 +1803,7 @@ static void ppc_spapr_init(MachineState *machine)
/* Setup a load limit for the ramdisk leaving room for SLOF and FDT */ /* Setup a load limit for the ramdisk leaving room for SLOF and FDT */
load_limit = MIN(spapr->rma_size, RTAS_MAX_ADDR) - FW_OVERHEAD; load_limit = MIN(spapr->rma_size, RTAS_MAX_ADDR) - FW_OVERHEAD;
/* We aim for a hash table of size 1/128 the size of RAM. The spapr->htab_shift = spapr_hpt_shift_for_ramsize(machine->maxram_size);
* normal rule of thumb is 1/64 the size of RAM, but that's much
* more than needed for the Linux guests we support. */
spapr->htab_shift = 18; /* Minimum architected size */
while (spapr->htab_shift <= 46) {
if ((1ULL << (spapr->htab_shift + 7)) >= machine->maxram_size) {
break;
}
spapr->htab_shift++;
}
spapr_alloc_htab(spapr); spapr_alloc_htab(spapr);
/* Set up Interrupt Controller before we create the VCPUs */ /* Set up Interrupt Controller before we create the VCPUs */