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SubjectRe: [RFC][QEMU Patch] KVM: Enable QEMU to free the pages hinted by the guest
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On 3/6/19 7:35 PM, Alexander Duyck wrote:
> Here are some changes I made to your patch in order to address the sizing
> issue I called out. You may want to try testing with this patch applied to
> your QEMU as I am finding it is making a signficant difference. It has cut
> the test time for the 32G memhog test I called out earlier in half.
Thanks, I will try this out.
>
> Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
> ---
> hw/virtio/virtio-balloon.c | 28 +++++++++++++++++-----------
> 1 file changed, 17 insertions(+), 11 deletions(-)
>
> diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
> index d2cf66ada3c0..3ca6b1c6d511 100644
> --- a/hw/virtio/virtio-balloon.c
> +++ b/hw/virtio/virtio-balloon.c
> @@ -285,7 +285,7 @@ static void balloon_stats_set_poll_interval(Object *obj, Visitor *v,
> balloon_stats_change_timer(s, 0);
> }
>
> -static void *gpa2hva(MemoryRegion **p_mr, hwaddr addr, Error **errp)
> +static void *gpa2hva(MemoryRegion **p_mr, unsigned long *size, hwaddr addr, Error **errp)
> {
> MemoryRegionSection mrs = memory_region_find(get_system_memory(),
> addr, 1);
> @@ -302,6 +302,7 @@ static void *gpa2hva(MemoryRegion **p_mr, hwaddr addr, Error **errp)
> }
>
> *p_mr = mrs.mr;
> + *size = mrs.mr->size - mrs.offset_within_region;
> return qemu_map_ram_ptr(mrs.mr->ram_block, mrs.offset_within_region);
> }
>
> @@ -313,30 +314,35 @@ void page_hinting_request(uint64_t addr, uint32_t len)
> struct guest_pages *guest_obj;
> int i = 0;
> void *hvaddr_to_free;
> - unsigned long pfn, pfn_end;
> uint64_t gpaddr_to_free;
> - void * temp_addr = gpa2hva(&mr, addr, &local_err);
> + unsigned long madv_size, size;
> + void * temp_addr = gpa2hva(&mr, &madv_size, addr, &local_err);
>
> if (local_err) {
> error_report_err(local_err);
> return;
> }
> + if (madv_size < sizeof(*guest_obj)) {
> + printf("\nBad guest object ptr\n");
> + return;
> + }
> guest_obj = temp_addr;
> while (i < len) {
> - pfn = guest_obj[i].pfn;
> - pfn_end = guest_obj[i].pfn + (1 << guest_obj[i].order) - 1;
> - trace_virtio_balloon_hinting_request(pfn,(1 << guest_obj[i].order));
> - while (pfn <= pfn_end) {
> - gpaddr_to_free = pfn << VIRTIO_BALLOON_PFN_SHIFT;
> - hvaddr_to_free = gpa2hva(&mr, gpaddr_to_free, &local_err);
> + gpaddr_to_free = guest_obj[i].pfn << VIRTIO_BALLOON_PFN_SHIFT;
> + size = (1 << VIRTIO_BALLOON_PFN_SHIFT) << guest_obj[i].order;
> + while (size) {
> + hvaddr_to_free = gpa2hva(&mr, &madv_size, gpaddr_to_free, &local_err);
> if (local_err) {
> error_report_err(local_err);
> return;
> }
> - ret = qemu_madvise((void *)hvaddr_to_free, 4096, QEMU_MADV_DONTNEED);
> + if (size < madv_size)
> + madv_size = size;
> + ret = qemu_madvise((void *)hvaddr_to_free, madv_size, QEMU_MADV_DONTNEED);
> if (ret == -1)
> printf("\n%d:%s Error: Madvise failed with error:%d\n", __LINE__, __func__, ret);
> - pfn++;
> + gpaddr_to_free += madv_size;
> + size -= madv_size;
> }
> i++;
> }
>
--
Regards
Nitesh

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