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Re: [Qemu-devel] [PATCH 1/4] migration: keep bytes_xfer_prev init'd to z
From: |
Juan Quintela |
Subject: |
Re: [Qemu-devel] [PATCH 1/4] migration: keep bytes_xfer_prev init'd to zero |
Date: |
Tue, 30 May 2017 18:14:10 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/25.2 (gnu/linux) |
Felipe Franciosi <address@hidden> wrote:
> The first time migration_bitmap_sync() is called, bytes_xfer_prev is set
> to ram_state.bytes_transferred which is, at this point, zero. The next
> time migration_bitmap_sync() is called, an iteration has happened and
> bytes_xfer_prev is set to 'x' bytes. Most likely, more than one second
> has passed, so the auto converge logic will be triggered and
> bytes_xfer_now will also be set to 'x' bytes.
>
> This condition is currently masked by dirty_rate_high_cnt, which will
> wait for a few iterations before throttling. It would otherwise always
> assume zero bytes have been copied and therefore throttle the guest
> (possibly) prematurely.
>
> Given bytes_xfer_prev is only used by the auto convergence logic, it
> makes sense to only set its value after a check has been made against
> bytes_xfer_now.
>
> Signed-off-by: Felipe Franciosi <address@hidden>
Reviewed-by: Juan Quintela <address@hidden>