From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Cooper Subject: Re: [PATCH for-xen-4.5] console: increase initial conring size Date: Tue, 2 Dec 2014 15:03:04 +0000 Message-ID: <547DD4A8.2010002@citrix.com> References: <1417532274-28976-1-git-send-email-daniel.kiper@oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta5.messagelabs.com ([195.245.231.135]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1Xvozz-0006p8-Fs for xen-devel@lists.xenproject.org; Tue, 02 Dec 2014 15:04:19 +0000 In-Reply-To: <1417532274-28976-1-git-send-email-daniel.kiper@oracle.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Daniel Kiper , xen-devel@lists.xenproject.org Cc: keir@xen.org, ian.campbell@citrix.com, jbeulich@suse.com, stefano.stabellini@eu.citrix.com List-Id: xen-devel@lists.xenproject.org On 02/12/14 14:57, Daniel Kiper wrote: > In general initial conring size is sufficient. However, if log > level is increased on platforms which have e.g. huge number > of memory regions (I have an IBM System x3550 M2 with 8 GiB RAM > which has more than 200 entries in EFI memory map) then some > of earlier messages in console ring are overwritten. It means > that in case of issues deeper analysis can be hindered. Sadly > conring_size argument does not help because new console buffer > is allocated late on heap. It means that it is not possible to > allocate larger ring earlier. So, in this situation initial > conring size should be increased. My experiments showed that > even on not so big machines more than 26 KiB of free space are > needed for initial messages. In theory we could increase conring > size buffer to 32 KiB. However, I think that this value could be > too small for huge machines with large number of ACPI tables and > EFI memory regions. Hence, this patch increases initial conring > size to 64 KiB. > > Signed-off-by: Daniel Kiper For what it is worth, XenServer has been been using a 64k default console size for a very long time now. However, a change line this must include a change to docs/misc/xen-command-line.markdown ~Andrew > --- > xen/drivers/char/console.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/xen/drivers/char/console.c b/xen/drivers/char/console.c > index 2f03259..429d296 100644 > --- a/xen/drivers/char/console.c > +++ b/xen/drivers/char/console.c > @@ -67,7 +67,7 @@ custom_param("console_timestamps", parse_console_timestamps); > static uint32_t __initdata opt_conring_size; > size_param("conring_size", opt_conring_size); > > -#define _CONRING_SIZE 16384 > +#define _CONRING_SIZE 65536 > #define CONRING_IDX_MASK(i) ((i)&(conring_size-1)) > static char __initdata _conring[_CONRING_SIZE]; > static char *__read_mostly conring = _conring;