On Tue, May 03, 2011 at 12:36:58PM -0600, Alex Williamson wrote:
> When a phys memory client registers and we play catchup by walking
> the page tables, we can make a huge improvement in the number of
> times the set_memory callback is called by batching contiguous
> pages together. With a 4G guest, this reduces the number of callbacks
> at registration from 1048866 to 296.
>
> Signed-off-by: Alex Williamson <alex.william...@redhat.com>
> ---
>
> exec.c | 38 ++++++++++++++++++++++++++++++++------
> 1 files changed, 32 insertions(+), 6 deletions(-)
>
> diff --git a/exec.c b/exec.c
> index bbd5c86..a0678a4 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -1741,14 +1741,21 @@ static int cpu_notify_migration_log(int enable)
> return 0;
> }
>
> +struct last_map {
> + target_phys_addr_t start_addr;
> + ram_addr_t size;
A bit worried that ram_addr_t size might thinkably overflow
(it's just a long, could be a 4G ram). Break it out when it fills up?
> + ram_addr_t phys_offset;
> +};
> +
> /* The l1_phys_map provides the upper P_L1_BITs of the guest physical
> * address. Each intermediate table provides the next L2_BITs of guest
> * physical address space. The number of levels vary based on host and
> * guest configuration, making it efficient to build the final guest
> * physical address by seeding the L1 offset and shifting and adding in
> * each L2 offset as we recurse through them. */
> -static void phys_page_for_each_1(CPUPhysMemoryClient *client,
> - int level, void **lp, target_phys_addr_t
> addr)
> +static void phys_page_for_each_1(CPUPhysMemoryClient *client, int level,
> + void **lp, target_phys_addr_t addr,
> + struct last_map *map)
> {
> int i;
>
> @@ -1760,15 +1767,29 @@ static void phys_page_for_each_1(CPUPhysMemoryClient
> *client,
> addr <<= L2_BITS + TARGET_PAGE_BITS;
> for (i = 0; i < L2_SIZE; ++i) {
> if (pd[i].phys_offset != IO_MEM_UNASSIGNED) {
> - client->set_memory(client, addr | i << TARGET_PAGE_BITS,
> - TARGET_PAGE_SIZE, pd[i].phys_offset);
> + target_phys_addr_t start_addr = addr | i << TARGET_PAGE_BITS;
> +
> + if (map->size &&
> + start_addr == map->start_addr + map->size &&
> + pd[i].phys_offset == map->phys_offset + map->size) {
> +
> + map->size += TARGET_PAGE_SIZE;
> + continue;
> + } else if (map->size) {
> + client->set_memory(client, map->start_addr,
> + map->size, map->phys_offset);
> + }
> +
> + map->start_addr = start_addr;
> + map->size = TARGET_PAGE_SIZE;
> + map->phys_offset = pd[i].phys_offset;
> }
> }
> } else {
> void **pp = *lp;
> for (i = 0; i < L2_SIZE; ++i) {
> phys_page_for_each_1(client, level - 1, pp + i,
> - (addr << L2_BITS) | i);
> + (addr << L2_BITS) | i, map);
> }
> }
> }
> @@ -1776,9 +1797,14 @@ static void phys_page_for_each_1(CPUPhysMemoryClient
> *client,
> static void phys_page_for_each(CPUPhysMemoryClient *client)
> {
> int i;
> + struct last_map map = { 0 };
> +
Nit: just {} is enough.
> for (i = 0; i < P_L1_SIZE; ++i) {
> phys_page_for_each_1(client, P_L1_SHIFT / L2_BITS - 1,
> - l1_phys_map + i, i);
> + l1_phys_map + i, i, &map);
> + }
> + if (map.size) {
> + client->set_memory(client, map.start_addr, map.size,
> map.phys_offset);
> }
> }
>
