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From: Kent Overstreet <koverstreet-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
To: Joseph Glanville
	<joseph.glanville-2MxvZkOi9dvvnOemgxGiVw@public.gmane.org>
Cc: linux-bcache-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: Kernel panic with current bcache-3.2 branch.
Date: Thu, 16 Aug 2012 16:36:00 -0700	[thread overview]
Message-ID: <20120816233600.GB26564@google.com> (raw)
In-Reply-To: <CAOzFzEhJ1PtpbKTbkh=8XTNDdFnjgWP6qBCwQHzXhO8C9s-eyw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>

On Thu, Aug 16, 2012 at 10:07:29PM +1000, Joseph Glanville wrote:
> There also seems to have been pretty severe performance regressions in
> cache bypassed sequential I/O.
> The newer code barely does 70mb/s sequential writes when
> sequential_cuttoff is set to 4M however it does around 300mb/s when
> set to 0 (no bypass) with dd and 1M block size.
> When using the older codebase the cache bypass is actually slightly
> faster than going to cache at around 360mb/s but this is still much
> slower than the underlying block devices (as previously discussed).

Ouch. Can you try profiling it with perf while running dd?

perf record -afg dd etc. etc.
perf report

should do it

  parent reply	other threads:[~2012-08-16 23:36 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-08-16  8:51 Kernel panic with current bcache-3.2 branch Joseph Glanville
     [not found] ` <CAOzFzEiS3MWe39C+XinBP3fN-Kw8Hs6n3oyqixrMVZpsuMhLcw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2012-08-16 11:34   ` Joseph Glanville
     [not found]     ` <CAOzFzEim7Q7eDr2z=BNsgnUuYH-XJaCPYpeVt5zkE1kvxZn+RQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2012-08-16 12:07       ` Joseph Glanville
     [not found]         ` <CAOzFzEhJ1PtpbKTbkh=8XTNDdFnjgWP6qBCwQHzXhO8C9s-eyw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2012-08-16 23:36           ` Kent Overstreet [this message]
     [not found]             ` <20120816233600.GB26564-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2012-08-17  4:07               ` Joseph Glanville
2012-08-16 23:34   ` Kent Overstreet
     [not found]     ` <20120816233457.GA26564-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2012-08-17  0:19       ` Jonathan Tripathy
     [not found]         ` <502D8E28.9090401-Nf8S+5hNwl710XsdtD+oqA@public.gmane.org>
2012-08-17  0:23           ` Jonathan Tripathy
2012-08-17  4:06       ` Joseph Glanville

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