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Date: Tue, 13 Oct 2015 16:42:33 +0100
From: Stefan Hajnoczi <stefanha@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v2 07/22] block: Add statistics for failed
 and invalid I/O operations
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To: Alberto Garcia <berto@igalia.com>
Cc: Kevin Wolf <kwolf@redhat.com>, qemu-block@nongnu.org, Markus Armbruster <armbru@redhat.com>, qemu-devel@nongnu.org, Max Reitz <mreitz@redhat.com>

On Fri, Oct 02, 2015 at 05:26:17PM +0300, Alberto Garcia wrote:
> +void block_acct_failed(BlockAcctStats *stats, BlockAcctCookie *cookie)
> +{
> +    int64_t time_ns = qemu_clock_get_ns(clock_type);
> +
> +    assert(cookie->type < BLOCK_MAX_IOTYPE);
> +
> +    stats->failed_ops[cookie->type]++;
> +    stats->total_time_ns[cookie->type] += time_ns - cookie->start_time_ns;
> +    stats->last_access_time_ns = time_ns;
> +}
> +
> +void block_acct_invalid(BlockAcctStats *stats, enum BlockAcctType type)
> +{
> +    assert(type < BLOCK_MAX_IOTYPE);
> +
> +    stats->invalid_ops[type]++;
> +    stats->last_access_time_ns = qemu_clock_get_ns(clock_type);
> +}

block_acct_failed() updates total_time_ns[] but block_acct_invalid()
does not.  I guess that's because block_acct_invalid() is expected to
happen during request submission and has effectively 0 duration?

This deserves a comment.