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[PULL 30/30] softmmu/memory_mapping: optimize for RamDiscardManager sect
From: |
Paolo Bonzini |
Subject: |
[PULL 30/30] softmmu/memory_mapping: optimize for RamDiscardManager sections |
Date: |
Sun, 3 Oct 2021 09:42:50 +0200 |
From: David Hildenbrand <david@redhat.com>
virtio-mem logically plugs/unplugs memory within a sparse memory region
and notifies via the RamDiscardManager interface when parts become
plugged (populated) or unplugged (discarded).
Currently, we end up (via the two users)
1) zeroing all logically unplugged/discarded memory during TPM resets.
2) reading all logically unplugged/discarded memory when dumping, to
figure out the content is zero.
1) is always bad, because we assume unplugged memory stays discarded
(and is already implicitly zero).
2) isn't that bad with anonymous memory, we end up reading the zero
page (slow and unnecessary, though). However, once we use some
file-backed memory (future use case), even reading will populate memory.
Let's cut out all parts marked as not-populated (discarded) via the
RamDiscardManager. As virtio-mem is the single user, this now means that
logically unplugged memory ranges will no longer be included in the
dump, which results in smaller dump files and faster dumping.
virtio-mem has a minimum granularity of 1 MiB (and the default is usually
2 MiB). Theoretically, we can see quite some fragmentation, in practice
we won't have it completely fragmented in 1 MiB pieces. Still, we might
end up with many physical ranges.
Both, the ELF format and kdump seem to be ready to support many
individual ranges (e.g., for ELF it seems to be UINT32_MAX, kdump has a
linear bitmap).
Reviewed-by: Peter Xu <peterx@redhat.com>
Cc: Marc-André Lureau <marcandre.lureau@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Claudio Fontana <cfontana@suse.de>
Cc: Thomas Huth <thuth@redhat.com>
Cc: "Alex Bennée" <alex.bennee@linaro.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Laurent Vivier <lvivier@redhat.com>
Cc: Stefan Berger <stefanb@linux.ibm.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20210727082545.17934-5-david@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
softmmu/memory_mapping.c | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)
diff --git a/softmmu/memory_mapping.c b/softmmu/memory_mapping.c
index a2af02c41c..a62eaa49cc 100644
--- a/softmmu/memory_mapping.c
+++ b/softmmu/memory_mapping.c
@@ -246,6 +246,15 @@ static void guest_phys_block_add_section(GuestPhysListener
*g,
#endif
}
+static int guest_phys_ram_populate_cb(MemoryRegionSection *section,
+ void *opaque)
+{
+ GuestPhysListener *g = opaque;
+
+ guest_phys_block_add_section(g, section);
+ return 0;
+}
+
static void guest_phys_blocks_region_add(MemoryListener *listener,
MemoryRegionSection *section)
{
@@ -257,6 +266,17 @@ static void guest_phys_blocks_region_add(MemoryListener
*listener,
memory_region_is_nonvolatile(section->mr)) {
return;
}
+
+ /* for special sparse regions, only add populated parts */
+ if (memory_region_has_ram_discard_manager(section->mr)) {
+ RamDiscardManager *rdm;
+
+ rdm = memory_region_get_ram_discard_manager(section->mr);
+ ram_discard_manager_replay_populated(rdm, section,
+ guest_phys_ram_populate_cb, g);
+ return;
+ }
+
guest_phys_block_add_section(g, section);
}
--
2.31.1
- [PULL 19/30] i386: Move HV_APIC_ACCESS_RECOMMENDED bit setting to hyperv_fill_cpuids(), (continued)
- [PULL 19/30] i386: Move HV_APIC_ACCESS_RECOMMENDED bit setting to hyperv_fill_cpuids(), Paolo Bonzini, 2021/10/03
- [PULL 21/30] i386: Make Hyper-V version id configurable, Paolo Bonzini, 2021/10/03
- [PULL 20/30] i386: Implement pseudo 'hv-avic' ('hv-apicv') enlightenment, Paolo Bonzini, 2021/10/03
- [PULL 23/30] configure: Loosen GCC requirement from 7.5.0 to 7.4.0, Paolo Bonzini, 2021/10/03
- [PULL 24/30] virtio-mem-pci: Fix memory leak when creating MEMORY_DEVICE_SIZE_CHANGE event, Paolo Bonzini, 2021/10/03
- [PULL 27/30] tpm: mark correct memory region range dirty when clearing RAM, Paolo Bonzini, 2021/10/03
- [PULL 26/30] monitor: Rate-limit MEMORY_DEVICE_SIZE_CHANGE qapi events per device, Paolo Bonzini, 2021/10/03
- [PULL 25/30] qapi: Include qom-path in MEMORY_DEVICE_SIZE_CHANGE qapi events, Paolo Bonzini, 2021/10/03
- [PULL 28/30] softmmu/memory_mapping: never merge ranges accross memory regions, Paolo Bonzini, 2021/10/03
- [PULL 29/30] softmmu/memory_mapping: factor out adding physical memory ranges, Paolo Bonzini, 2021/10/03
- [PULL 30/30] softmmu/memory_mapping: optimize for RamDiscardManager sections,
Paolo Bonzini <=
- Re: [PULL 00/30] Misc changes for 2021-10-03, Philippe Mathieu-Daudé, 2021/10/03
- Re: [PULL 00/30] Misc changes for 2021-10-03, Richard Henderson, 2021/10/03