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Re: [Qemu-trivial] [PATCH v4 01/11] tcg: add ability to dump /tmp/perf-<

From: Alex Bennée
Subject: Re: [Qemu-trivial] [PATCH v4 01/11] tcg: add ability to dump /tmp/perf-<pid>.map files
Date: Tue, 04 Aug 2015 08:39:45 +0100

Paolo Bonzini <address@hidden> writes:

> On 03/08/2015 11:14, Alex Bennée wrote:
>> This allows the perf tool to map samples to each individual translation
>> block. This could be expanded for user space but currently it gives
>> enough information to find any hotblocks by other means.
>> Signed-off-by: Alex Bennée <address@hidden>
> What happens if you encounter a tb_flush?

At the point of a tb_flush all bets are off as we will re-generate all
the blocks at potentially different locations in the translation buffer.
However for most analysis cases you are unlikely to cause the code
buffer to overflow. Most other uses of tb_flush are the result

I could add a printf when --perfmap is enabled to flag when a flush
happens to signal to the user? I guess some more caveats in the flag
description wouldn't hurt.

We could consider truncating and re-starting the JIT dump at each flush?

> Paolo

Alex Bennée

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