[PATCH 0/3] makedumpfile: calculate the size of cyclic buffer automatically.

[Atsushi Kumagai]

Hello,

On Fri, 09 Nov 2012 03:46:21 -0700
Lisa Mitchell <lisa.mitchell at hp.com> wrote:

> On Fri, 2012-11-09 at 14:17 +0000, Vivek Goyal wrote:
> > On Fri, Nov 09, 2012 at 04:02:14PM +0900, Atsushi Kumagai wrote:
> > > Hello,
> > > 
> > > I made the patch set based on v1.5.1-beta to calculate the size of cyclic 
> > > buffer automatically.
> > > 
> > > In v1.5.0, users have to specify the buffer size depending on system memory
> > > size with --cyclic-buffer option in order to get decent performance.
> > > 
> > > This patch set avoids the inconvenience above by choosing the lesser value
> > > of the two below as the size of cyclic buffer automatically:
> > > 
> > >   a. the size enough for storing the 1st/2nd bitmap for the whole of vmcore
> > >   b. 80% of free memory (as safety limit)
> > > 
> > > Additionally, this patch set remove --cyclic-buffer option because I think
> > > it has been already unnecessary.
> > 
> > I was wondering how about retaining --cyclic-buffer <size> option. If 
> > there are use cases where user's don't like default of 80% of free memory
> > they can override this policy by specifying --cyclic-buffer.
> > 
> > Thanks
> > Vivek
> 
> I second that, I'd like the --cyclic-buffer option to stay.  I see PATCH
> 3/3 to remove cyclic buffer option, and I also would like it left there,
> for debug of issues that may come up later.  It's great that the code
> will automatically calculate the best cyclic buffer option, which is
> what it should do for the best customer out-of-the-box dump enablement,
> but the ability to manipulate it for debug purposes, or for workarounds
> if things go wrong, is valuable.

OK, I understand that --cyclic-buffer option is still needed, so I will 
retain it by removing the [PATCH 3/3].

Additionally, I will change [PATCH 2/3] as below because I think 100 MB
as safety limit is inconvenient for debugging.


Thanks
Atsushi Kumagai


diff --git a/makedumpfile.c b/makedumpfile.c
index 9c17280..8fa718f 100644
--- a/makedumpfile.c
+++ b/makedumpfile.c
@@ -2721,17 +2721,27 @@ out:
                if (info->bufsize_cyclic == 0) {
                        if (!calculate_cyclic_buffer_size())
                                return FALSE;
-               } else
+               } else {
+                       unsigned long long free_memory;
+
+                       /*
+                        * The buffer size is specified as Kbyte with
+                        * --cyclic-buffer <size> option.
+                        */
                        info->bufsize_cyclic <<= 10;

-               /*
-                * Max buffer size is 100 MB
-                */
-               if (info->bufsize_cyclic > (100 << 20)) {
-                       MSG("Specified buffer size is too large, ");
-                       MSG("The buffer size for the cyclic mode will be truncated to 100 MB.\n");
-                       info->bufsize_cyclic = (100 << 20);
+                       /*
+                        * Truncate the buffer size to free memory size.
+                        */
+                       free_memory = get_free_memory_size();
+                       if (info->bufsize_cyclic > free_memory) {
+                               MSG("Specified buffer size is larger than free memory.");
+                               MSG("The buffer size for the cyclic mode will ");
+                               MSG("be truncated to %lld byte.\n", free_memory);
+                               info->bufsize_cyclic = free_memory;
+                       }
                }
+
                info->pfn_cyclic = info->bufsize_cyclic * BITPERBYTE;

                DEBUG_MSG("\n");