f952710757
Prior to servicing userfault requests we must ensure we've not got huge pages in the area that might include non-transferred memory, since a hugepage could incorrectly mark the whole huge page as present. We mark the area as non-huge page (nhp) just before we perform discards; the discard code now tells us to discard any areas that haven't been sent (as well as any that are redirtied); any already formed transparent-huge-pages get fragmented by this discard process if they cotnain any discards. Transparent huge pages that have been entirely transferred and don't contain any discards are not broken by this mechanism; they stay as huge pages. By starting postcopy after a full precopy pass, many of the pages then stay as huge pages; this is important for maintaining performance after the end of the migration. Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com> Reviewed-by: Juan Quintela <quintela@redhat.com> Signed-off-by: Juan Quintela <quintela@redhat.com>
100 lines
3.2 KiB
C
100 lines
3.2 KiB
C
/*
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* Postcopy migration for RAM
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*
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* Copyright 2013 Red Hat, Inc. and/or its affiliates
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*
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* Authors:
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* Dave Gilbert <dgilbert@redhat.com>
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*
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* This work is licensed under the terms of the GNU GPL, version 2 or later.
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* See the COPYING file in the top-level directory.
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*
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*/
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#ifndef QEMU_POSTCOPY_RAM_H
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#define QEMU_POSTCOPY_RAM_H
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/* Return true if the host supports everything we need to do postcopy-ram */
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bool postcopy_ram_supported_by_host(void);
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/*
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* Make all of RAM sensitive to accesses to areas that haven't yet been written
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* and wire up anything necessary to deal with it.
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*/
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int postcopy_ram_enable_notify(MigrationIncomingState *mis);
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/*
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* Initialise postcopy-ram, setting the RAM to a state where we can go into
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* postcopy later; must be called prior to any precopy.
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* called from ram.c's similarly named ram_postcopy_incoming_init
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*/
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int postcopy_ram_incoming_init(MigrationIncomingState *mis, size_t ram_pages);
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/*
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* At the end of a migration where postcopy_ram_incoming_init was called.
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*/
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int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis);
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/*
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* Discard the contents of 'length' bytes from 'start'
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* We can assume that if we've been called postcopy_ram_hosttest returned true
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*/
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int postcopy_ram_discard_range(MigrationIncomingState *mis, uint8_t *start,
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size_t length);
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/*
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* Userfault requires us to mark RAM as NOHUGEPAGE prior to discard
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* however leaving it until after precopy means that most of the precopy
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* data is still THPd
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*/
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int postcopy_ram_prepare_discard(MigrationIncomingState *mis);
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/*
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* Called at the start of each RAMBlock by the bitmap code.
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* 'offset' is the bitmap offset of the named RAMBlock in the migration
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* bitmap.
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* Returns a new PDS
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*/
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PostcopyDiscardState *postcopy_discard_send_init(MigrationState *ms,
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unsigned long offset,
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const char *name);
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/*
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* Called by the bitmap code for each chunk to discard.
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* May send a discard message, may just leave it queued to
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* be sent later.
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* @start,@length: a range of pages in the migration bitmap in the
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* RAM block passed to postcopy_discard_send_init() (length=1 is one page)
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*/
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void postcopy_discard_send_range(MigrationState *ms, PostcopyDiscardState *pds,
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unsigned long start, unsigned long length);
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/*
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* Called at the end of each RAMBlock by the bitmap code.
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* Sends any outstanding discard messages, frees the PDS.
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*/
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void postcopy_discard_send_finish(MigrationState *ms,
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PostcopyDiscardState *pds);
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/*
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* Place a page (from) at (host) efficiently
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* There are restrictions on how 'from' must be mapped, in general best
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* to use other postcopy_ routines to allocate.
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* returns 0 on success
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*/
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int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from);
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/*
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* Place a zero page at (host) atomically
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* returns 0 on success
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*/
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int postcopy_place_page_zero(MigrationIncomingState *mis, void *host);
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/*
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* Allocate a page of memory that can be mapped at a later point in time
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* using postcopy_place_page
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* Returns: Pointer to allocated page
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*/
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void *postcopy_get_tmp_page(MigrationIncomingState *mis);
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#endif
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