All of lore.kernel.org
 help / color / mirror / Atom feed
From: Peter Maydell <peter.maydell@linaro.org>
To: Pavel Dovgaluk <Pavel.Dovgaluk@ispras.ru>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
	Peter Crosthwaite <peter.crosthwaite@xilinx.com>,
	Mark Burton <mark.burton@greensocs.com>,
	QEMU Developers <qemu-devel@nongnu.org>,
	Frederic Konrad <fred.konrad@greensocs.com>
Subject: Re: [Qemu-devel] Reverse execution and deterministic replay
Date: Fri, 27 Jun 2014 11:54:47 +0100	[thread overview]
Message-ID: <CAFEAcA8-5J9ouJREJT=hF1q-dqBd=0JoGz6gG4wBuKbJ7zSOKA@mail.gmail.com> (raw)
In-Reply-To: <53ad4904.8360e50a.0f7f.ffffce7dSMTPIN_ADDED_BROKEN@mx.google.com>

On 27 June 2014 11:35, Pavel Dovgaluk <Pavel.Dovgaluk@ispras.ru> wrote:
> The major disadvantage of icount is that it's updated only on TB boundaries.
> When one instruction in the middle of the block uses virtual clock, it could
> have different values for different divisions of the code to TB.

This is only true if the instruction is incorrectly not
marked as being "I/O". The idea behind icount is that in
general we update it on TB boundaries (it's much faster
than doing it once per insn) but for those places which
do turn out to need an exact icount we then retranslate
the block to get the instruction-to-icount-adjustment
mapping.

It wouldn't surprise me if this turned out to have some
bugs in corner cases, but fixing these issues seems to
me like a much better design than ignoring icount completely
and reimplementing a second instruction counter.

thanks
-- PMM

  parent reply	other threads:[~2014-06-27 10:55 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <53acfed7.e3538c0a.39e2.ffffb619SMTPIN_ADDED_BROKEN@mx.google.com>
2014-06-27  6:11 ` [Qemu-devel] Reverse execution and deterministic replay Peter Crosthwaite
2014-06-27  6:20   ` Pavel Dovgaluk
2014-06-27  7:47   ` Frederic Konrad
2014-06-27 10:35     ` Pavel Dovgaluk
     [not found]     ` <53ad4904.8360e50a.0f7f.ffffce7dSMTPIN_ADDED_BROKEN@mx.google.com>
2014-06-27 10:54       ` Peter Maydell [this message]
2014-06-27 11:17         ` Pavel Dovgaluk
2014-06-27 13:43           ` Frederic Konrad
2014-06-27 11:31         ` Pavel Dovgaluk
     [not found]         ` <53ad5626.82a3700a.2864.fffffc92SMTPIN_ADDED_BROKEN@mx.google.com>
2014-06-27 11:50           ` Peter Maydell
     [not found] <53acfecd.c842e00a.6a5f.45f1SMTPIN_ADDED_BROKEN@mx.google.com>
2014-06-27  8:27 ` Peter Maydell
2014-06-27  5:18 Pavel Dovgaluk

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to='CAFEAcA8-5J9ouJREJT=hF1q-dqBd=0JoGz6gG4wBuKbJ7zSOKA@mail.gmail.com' \
    --to=peter.maydell@linaro.org \
    --cc=Pavel.Dovgaluk@ispras.ru \
    --cc=fred.konrad@greensocs.com \
    --cc=mark.burton@greensocs.com \
    --cc=pbonzini@redhat.com \
    --cc=peter.crosthwaite@xilinx.com \
    --cc=qemu-devel@nongnu.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.