From mboxrd@z Thu Jan  1 00:00:00 1970
From: Olaf Hering <olaf@aepfle.de>
Subject: Re: xentrace: broken by c/s 23050:4ebba54b666f
Date: Mon, 21 Mar 2011 22:23:20 +0100
Message-ID: <20110321212320.GA15820@aepfle.de>
References: <4D87841B.1000102@amd.com>
 <20110321173859.GA21766@aepfle.de>
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To: Christoph Egger <Christoph.Egger@amd.com>
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On Mon, Mar 21, Olaf Hering wrote:

> On Mon, Mar 21, Christoph Egger wrote:
> 
> > 
> > Hi,
> > 
> > C/s 23050:4ebba54b666f broke xentrace:
> > 
> > # xentrace -e 0x8f000 ./xentrace.out
> > (XEN) Xen trace buffers: cpu 0 p 0000000000000000
> 
> The system you test on has 8 cpus, like mine.
> t_info_pages got too big, so alloc_xenheap_pages() failed.
> Can you add a printk to se whats happening in calculate_tbuf_size()?

compile tested patch:


# HG changeset patch
# Parent c81f0ef5a77d90fbf108d3efe489d08df45b63c2
xentrace: print calculated numbers in calculate_tbuf_size()

Print number of pages to allocate for per-cpu tracebuffer and metadata
to ease debugging when allocation fails.

Signed-off-by: Olaf Hering <olaf@aepfle.de>

diff -r c81f0ef5a77d xen/common/trace.c
--- a/xen/common/trace.c	Mon Mar 21 14:52:27 2011 +0000
+++ b/xen/common/trace.c	Mon Mar 21 21:49:52 2011 +0100
@@ -127,6 +127,8 @@
     t_info_pages /= PAGE_SIZE;
     if ( t_info_pages % PAGE_SIZE )
         t_info_pages++;
+    gdprintk(XENLOG_INFO, "requested %u t_info_pages for %u trace pages on %u cpus\n",
+               t_info_pages, pages, num_online_cpus());
     return pages;
 }