qemu/softmmu
David Hildenbrand cb83ba8c1a softmmu/memory_mapping: optimize for RamDiscardManager sections
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>
2021-10-02 08:43:22 +02:00
..
arch_init.c meson.build: Define QEMU_ARCH in config-target.h 2021-08-26 17:02:00 +01:00
balloon.c qapi: Restrict balloon-related commands to machine code 2020-09-29 15:41:35 +02:00
bootdevice.c softmmu: move more files to softmmu/ 2020-10-12 11:50:21 -04:00
cpu-throttle.c cpu-throttle: Remove timer_mod() from cpu_throttle_set() 2021-02-08 15:15:32 +01:00
cpu-timers.c icount: get rid of static variable 2021-04-01 09:40:45 +02:00
cpus.c misc: Remove redundant new line in perror() 2021-07-09 18:42:46 +02:00
datadir.c vl: extract softmmu/datadir.c 2020-12-10 12:15:18 -05:00
device_tree.c Do not include sysemu/sysemu.h if it's not really necessary 2021-05-02 17:24:50 +02:00
dma-helpers.c dma: Introduce dma_aligned_pow2_mask() 2021-03-12 12:40:10 +00:00
globals.c qmp: generalize watchdog-set-action to -no-reboot/-no-shutdown 2020-12-15 12:51:57 -05:00
icount.c icount: get rid of static variable 2021-04-01 09:40:45 +02:00
ioport.c softmmu: Add missing trace-events file 2020-09-09 17:15:18 +01:00
main.c meson: move SDL and SDL-image detection to meson 2020-08-21 06:30:44 -04:00
memory.c memory: Add tracepoint for dirty sync 2021-09-30 15:30:24 +02:00
memory_mapping.c softmmu/memory_mapping: optimize for RamDiscardManager sections 2021-10-02 08:43:22 +02:00
meson.build seccomp: convert to meson 2021-01-06 10:21:20 +01:00
physmem.c memory: Name all the memory listeners 2021-09-30 15:30:24 +02:00
qdev-monitor.c qdev: Support marking individual buses as 'full' 2021-09-13 21:01:08 +01:00
qemu-seccomp.c seccomp: don't block getters for resource control syscalls 2021-07-14 14:15:52 +01:00
qtest.c qtest: add a QOM object for qtest 2021-05-26 14:49:45 +02:00
rtc.c qom: Allow optional sugar props 2021-02-08 16:57:37 +11:00
runstate-action.c runstate: cleanup reboot and panic actions 2021-01-21 13:00:41 +01:00
runstate.c runstate: Initialize Error * to NULL 2021-06-15 17:17:09 +02:00
timers-state.h qemu/atomic: Add aligned_{int64,uint64}_t types 2021-07-21 07:45:38 -10:00
tpm.c qapi: More complex uses of QAPI_LIST_APPEND 2021-01-28 08:08:45 +01:00
trace-events memory: Add tracepoint for dirty sync 2021-09-30 15:30:24 +02:00
trace.h softmmu: Add missing trace-events file 2020-09-09 17:15:18 +01:00
vl.c softmmu/vl: Deprecate the -sdl and -curses option 2021-09-06 10:00:14 +02:00