From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:48736) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aSxmB-0006wj-Ta for qemu-devel@nongnu.org; Mon, 08 Feb 2016 21:11:36 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aSxm7-0000hH-RU for qemu-devel@nongnu.org; Mon, 08 Feb 2016 21:11:35 -0500 From: David Gibson Date: Tue, 9 Feb 2016 12:12:23 +1000 Message-Id: <1454983946-32073-5-git-send-email-david@gibson.dropbear.id.au> In-Reply-To: <1454983946-32073-1-git-send-email-david@gibson.dropbear.id.au> References: <1454983946-32073-1-git-send-email-david@gibson.dropbear.id.au> Subject: [Qemu-devel] [PATCHv2 4/7] pseries: Add helper to calculate recommended hash page table size List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: benh@kernel.crashing.org, aik@ozlabs.ru, agraf@suse.de Cc: qemu-ppc@nongnu.org, qemu-devel@nongnu.org, David Gibson 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 --- hw/ppc/spapr.c | 24 ++++++++++++++---------- 1 file changed, 14 insertions(+), 10 deletions(-) diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c index c315715..2a81e8f 100644 --- a/hw/ppc/spapr.c +++ b/hw/ppc/spapr.c @@ -1050,6 +1050,19 @@ static void close_htab_fd(sPAPRMachineState *spapr) 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) { 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 */ 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 - * 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->htab_shift = spapr_hpt_shift_for_ramsize(machine->maxram_size); spapr_alloc_htab(spapr); /* Set up Interrupt Controller before we create the VCPUs */ -- 2.5.0