From: Juan Quintela <quintela@redhat.com>
To: David Hildenbrand <david@redhat.com>
Cc: qemu-devel@nongnu.org,
"Dr. David Alan Gilbert" <dgilbert@redhat.com>,
Peter Xu <peterx@redhat.com>,
Andrey Gruzdev <andrey.gruzdev@virtuozzo.com>
Subject: Re: [PATCH v1 5/5] migration/ram: Optimize ram_write_tracking_start() for RamDiscardManager
Date: Thu, 02 Feb 2023 12:20:57 +0100 [thread overview]
Message-ID: <87fsboqpnq.fsf@secure.mitica> (raw)
In-Reply-To: <20230105124528.93813-6-david@redhat.com> (David Hildenbrand's message of "Thu, 5 Jan 2023 13:45:28 +0100")
David Hildenbrand <david@redhat.com> wrote:
> ram_block_populate_read() already optimizes for RamDiscardManager.
> However, ram_write_tracking_start() will still try protecting discarded
> memory ranges.
>
> Let's optimize, because discarded ranges don't map any pages and
>
> (1) For anonymous memory, trying to protect using uffd-wp without a mapped
> page is ignored by the kernel and consequently a NOP.
>
> (2) For shared/file-backed memory, we will fill present page tables in the
> range with PTE markers. However, we will even allocate page tables
> just to fill them with unnecessary PTE markers and effectively
> waste memory.
>
> So let's exclude these ranges, just like ram_block_populate_read()
> already does.
>
> Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
next prev parent reply other threads:[~2023-02-02 11:21 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-05 12:45 [PATCH v1 0/5] migration/ram: background snapshot fixes and optimiations David Hildenbrand
2023-01-05 12:45 ` [PATCH v1 1/5] migration/ram: Fix populate_read_range() David Hildenbrand
2023-02-02 11:15 ` Juan Quintela
2023-01-05 12:45 ` [PATCH v1 2/5] migration/ram: Fix error handling in ram_write_tracking_start() David Hildenbrand
2023-02-02 11:16 ` Juan Quintela
2023-01-05 12:45 ` [PATCH v1 3/5] migration/ram: Don't explicitly unprotect when unregistering uffd-wp David Hildenbrand
2023-02-02 11:17 ` Juan Quintela
2023-01-05 12:45 ` [PATCH v1 4/5] migration/ram: Rely on used_length for uffd_change_protection() David Hildenbrand
2023-02-02 11:18 ` Juan Quintela
2023-01-05 12:45 ` [PATCH v1 5/5] migration/ram: Optimize ram_write_tracking_start() for RamDiscardManager David Hildenbrand
2023-02-02 11:20 ` Juan Quintela [this message]
2023-01-05 21:11 ` [PATCH v1 0/5] migration/ram: background snapshot fixes and optimiations Peter Xu
2023-01-09 8:37 ` David Hildenbrand
2023-01-23 14:27 ` David Hildenbrand
2023-02-02 11:21 ` Juan Quintela
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