[Qemu-devel] Re: [kvm-devel] Slow Kernel Boot

[Amit Shah]

On Tuesday 08 January 2008 18:31:53 Amit Shah wrote:
> On Tuesday 08 January 2008 12:12:53 Amit Shah wrote:
> > On Tuesday 08 January 2008 03:35:48 Dave Hansen wrote:
> > > With kvm-44, I thought my kernel was freezing during boot if I gave it
> > > 1G of RAM.  But, it boots fine with 512M.
> > >
> > > So, I instrumented the kernel, and found out that it is just taking a
> > > long time to memset a 58MB area of memory for mem_map[].  It appears to
> > > be taking a mmio_exit for every access of every byte of memory.  The
> > > end result is a ~100kbps memset() speed.  Yes, 100 kilobytes/sec.
> > >
> > > I just tried kvm from git, and the kernel doesn't even get that far.  I
> > > see this in debugfs
> > >
> > >   insn_emulation:1393985
> > >
> > > even before I get a single kernel message.  And it keeps going up,
> > > fast. I can get the kernel to boot just fine if I give it less than
> > > 896MB of RAM.
> > >
> > > kvm-44 boots long enough for me to see a really funky e820 table:
> > >
> > > BIOS-provided physical RAM map:
> > >  BIOS-e820: 0000000000000000 - 000000000009fc00 (usable)
> > >  BIOS-e820: 000000000009fc00 - 00000000000a0000 (reserved)
> > >  BIOS-e820: 00000000000e8000 - 0000000000100000 (reserved)
> > >  BIOS-e820: 0000000000100000 - 00000000fffbd000 (usable)
> > >  BIOS-e820: 00000000fffbd000 - 00000000ffff0000 (reserved)
> > >
> > > Note that this is with '-m 1G'!!  It looks to me like one of those
> >
> > And there lies the problem. qemu doesn't understand suffixes like 'G'. If
> > you pass -m 1024, you'll boot just fine.
> >
> > This is really annoying of qemu (it should either accept that input
> > properly or bail out); a patch is welcome!
>
> Just wrote this.

CC qemu-devel and fix warning.

From f6da5a80d06fe33832c6210da95a2d031c5e67b9 Mon Sep 17 00:00:00 2001
From: Amit Shah <address@hidden>
Date: Tue, 8 Jan 2008 18:24:34 +0530
Subject: [PATCH] qemu: Add support for suffixes to the -m parameter

The -m parameter doesn't take suffixes like G or M currently
and it doesn't complain if such a suffix is given.

Add support for the G and M suffixes and update the usage
instructions appropriately.

Signed-off-by: Amit Shah <address@hidden>
---
 qemu/vl.c |   25 +++++++++++++++++++++++--
 1 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/qemu/vl.c b/qemu/vl.c
index 0f023ac..2ed2469 100644
--- a/qemu/vl.c
+++ b/qemu/vl.c
@@ -7927,7 +7927,9 @@ static void help(int exitcode)
 #ifdef TARGET_I386
            "-no-fd-bootchk  disable boot signature checking for floppy 
disks\n"
 #endif
-           "-m megs         set virtual RAM size to megs MB [default=%d]\n"
+           "-m size         set virtual RAM size to size megs [default=%d 
MB].\n"
+           "                Optional suffixes 'M' (megabyte) and 'G' 
(gigabyte)"
+                            " are supported\n"
            "-smp n          set the number of CPUs to 'n' [default=1]\n"
            "-nographic      disable graphical output and redirect serial I/Os 
to console\n"
            "-portrait       rotate graphical output 90 deg left (only PXA 
LCD)\n"
@@ -8858,7 +8860,26 @@ int main(int argc, char **argv)
                 help(0);
                 break;
             case QEMU_OPTION_m:
-                ram_size = (int64_t)atoi(optarg) * 1024 * 1024;
+                errno = 0;
+                ram_size = (uint64_t) strtoul(optarg, (char **)&optarg, 0);
+                if (errno)
+                    help(1);
+                switch (*optarg) {
+                case 'G':
+                case 'g':
+                    ram_size *= 1024;
+                    /* fall through */
+                case 'M':
+                case 'm':
+                case '\0':
+                    ram_size *= 1024 * 1024;
+                    optarg++;
+                    break;
+                default:
+                    help(1);
+                    break;
+                }
+
                 if (ram_size <= 0)
                     help(1);
                 if (ram_size > PHYS_RAM_MAX_SIZE) {
-- 
1.5.2.5

0001-qemu-Add-support-for-suffixes-to-the-m-parameter.patch
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