[uml-devel] [PATCH] uml: move TMP default from /tmp to /dev/shm.

[uml-devel] [PATCH] uml: move TMP default from /tmp to /dev/shm.

[Rob Landley]

Signed-off-by: Rob Landley <rob@landley.net>

UML really wants shared memory semantics form its physical memory map file,
and the place for that is /dev/shm.  So move the default, and fix the error
messages to recognize that this value can be overridden.
---
UML calls mmap() to allocate some "physical memory" it shares between
processes.  If we're not careful, every page of this memory that gets dirtied
is pointelessly scheduled for writeout, which means an active user mode
instance running a compiler or some such can keep the disk pegged with
unnecessary I/O and slow the rest of the system to a crawl.

Back under 2.4 there was a performance hack that if you deleted a file you had
open and mmaped, dirty pages wouldn't get written out anymore unless they were
evicted due to memory pressure.  This hack got yanked sometime during 2.5, and
now you're supposed to use tmpfs if you want file-backed memory you can dirty
without causing unnecessary write I/O.

UML assumed that /tmp would be tmpfs, but this turns out not to be the default
on the systems I checked (Fedora Core 4, Ubuntu, and Gentoo).  But all of
these systems _do_ default to having a tmpfs mount on /dev/shm, which makes
sense since tmpfs used to be shmfs.  So that's a more logical default location
for UML's physical memory file.

(You can override the default location with the TMPDIR environment variable,
but you can't create a new tmpdir mount without root access, and running UML
should never require that.)

One function is moved to another file, but the only changes are to its 
printf()s.

diff -ur linux-2.6.15-rc2/arch/um-old/os-Linux/mem.c 
linux-2.6.15-rc2/arch/um/os-Linux/mem.c
--- linux-2.6.15-rc2/arch/um-old/os-Linux/mem.c 2005-11-23 02:35:49.000000000 
-0600
+++ linux-2.6.15-rc2/arch/um/os-Linux/mem.c 2005-11-28 09:33:21.158395976 
-0600
@@ -34,7 +34,7 @@
    break;
  }
  if((dir == NULL) || (*dir == '\0'))
-  dir = "/tmp";
+  dir = "/dev/shm";
 
  tempdir = malloc(strlen(dir) + 2);
  if(tempdir == NULL){
@@ -159,3 +159,26 @@
  }
  return(fd);
 }
+
+
+void check_tmpexec(void)
+{
+ void *addr;
+ int err, fd = create_tmp_file(UM_KERN_PAGE_SIZE);
+
+ addr = mmap(NULL, UM_KERN_PAGE_SIZE,
+      PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE, fd, 0);
+ printf("Checking PROT_EXEC mmap in %s...",tempdir);
+ fflush(stdout);
+ if(addr == MAP_FAILED){
+  err = errno;
+  perror("failed");
+  if(err == EPERM)
+   printf("%s must be not mounted noexec\n",tempdir);
+  exit(1);
+ }
+ printf("OK\n");
+ munmap(addr, UM_KERN_PAGE_SIZE);
+
+ close(fd);
+}
diff -ur linux-2.6.15-rc2/arch/um-old/os-Linux/start_up.c 
linux-2.6.15-rc2/arch/um/os-Linux/start_up.c
--- linux-2.6.15-rc2/arch/um-old/os-Linux/start_up.c 2005-11-23 
02:35:49.000000000 -0600
+++ linux-2.6.15-rc2/arch/um/os-Linux/start_up.c 2005-11-28 09:41:04.051025600 
-0600
@@ -296,29 +296,7 @@
  check_sysemu();
 }
 
-extern int create_tmp_file(unsigned long long len);
-
-static void check_tmpexec(void)
-{
- void *addr;
- int err, fd = create_tmp_file(UM_KERN_PAGE_SIZE);
-
- addr = mmap(NULL, UM_KERN_PAGE_SIZE,
-      PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE, fd, 0);
- printf("Checking PROT_EXEC mmap in /tmp...");
- fflush(stdout);
- if(addr == MAP_FAILED){
-  err = errno;
-  perror("failed");
-  if(err == EPERM)
-   printf("/tmp must be not mounted noexec\n");
-  exit(1);
- }
- printf("OK\n");
- munmap(addr, UM_KERN_PAGE_SIZE);
-
- close(fd);
-}
+extern void check_tmpexec(void);
 
 void os_early_checks(void)
 {


-- 
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I do not think it means what you think it means.


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[uml-devel] [PATCH] uml: move TMP default from /tmp to /dev/shm.

[Rob Landley]

Signed-off-by: Rob Landley <rob@landley.net>

UML really wants shared memory semantics form its physical memory map file,
and the place for that is /dev/shm.  So move the default, and fix the error
messages to recognize that this value can be overridden.
---
Let's try that again with wordrap off...


UML calls mmap() to allocate some "physical memory" it shares between
processes.  If we're not careful, every page of this memory that gets dirtied
is pointelessly scheduled for writeout, which means an active user mode
instance running a compiler or some such can keep the disk pegged with
unnecessary I/O and slow the rest of the system to a crawl.

Back under 2.4 there was a performance hack that if you deleted a file you had
open and mmaped, dirty pages wouldn't get written out anymore unless they were
evicted due to memory pressure.  This hack got yanked sometime during 2.5, and
now you're supposed to use tmpfs if you want file-backed memory you can dirty
without causing unnecessary write I/O.

UML assumed that /tmp would be tmpfs, but this turns out not to be the default
on the systems I checked (Fedora Core 4, Ubuntu, and Gentoo).  But all of
these systems _do_ default to having a tmpfs mount on /dev/shm, which makes
sense since tmpfs used to be shmfs.  So that's a more logical default location
for UML's physical memory file.

(You can override the default location with the TMPDIR environment variable,
but you can't create a new tmpdir mount without root access, and running UML
should never require that.)

One function is moved to another file, but the only changes are to its 
printf()s.

diff -ur linux-2.6.15-rc2/arch/um-old/os-Linux/mem.c linux-2.6.15-rc2/arch/um/os-Linux/mem.c
--- linux-2.6.15-rc2/arch/um-old/os-Linux/mem.c 2005-11-23 02:35:49.000000000 -0600
+++ linux-2.6.15-rc2/arch/um/os-Linux/mem.c 2005-11-28 09:33:21.158395976 -0600
@@ -34,7 +34,7 @@
    break;
  }
  if((dir == NULL) || (*dir == '\0'))
-  dir = "/tmp";
+  dir = "/dev/shm";
 
  tempdir = malloc(strlen(dir) + 2);
  if(tempdir == NULL){
@@ -159,3 +159,26 @@
  }
  return(fd);
 }
+
+
+void check_tmpexec(void)
+{
+ void *addr;
+ int err, fd = create_tmp_file(UM_KERN_PAGE_SIZE);
+
+ addr = mmap(NULL, UM_KERN_PAGE_SIZE,
+      PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE, fd, 0);
+ printf("Checking PROT_EXEC mmap in %s...",tempdir);
+ fflush(stdout);
+ if(addr == MAP_FAILED){
+  err = errno;
+  perror("failed");
+  if(err == EPERM)
+   printf("%s must be not mounted noexec\n",tempdir);
+  exit(1);
+ }
+ printf("OK\n");
+ munmap(addr, UM_KERN_PAGE_SIZE);
+
+ close(fd);
+}
diff -ur linux-2.6.15-rc2/arch/um-old/os-Linux/start_up.c linux-2.6.15-rc2/arch/um/os-Linux/start_up.c
--- linux-2.6.15-rc2/arch/um-old/os-Linux/start_up.c 2005-11-23 02:35:49.000000000 -0600
+++ linux-2.6.15-rc2/arch/um/os-Linux/start_up.c 2005-11-28 09:41:04.051025600 -0600
@@ -296,29 +296,7 @@
  check_sysemu();
 }
 
-extern int create_tmp_file(unsigned long long len);
-
-static void check_tmpexec(void)
-{
- void *addr;
- int err, fd = create_tmp_file(UM_KERN_PAGE_SIZE);
-
- addr = mmap(NULL, UM_KERN_PAGE_SIZE,
-      PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE, fd, 0);
- printf("Checking PROT_EXEC mmap in /tmp...");
- fflush(stdout);
- if(addr == MAP_FAILED){
-  err = errno;
-  perror("failed");
-  if(err == EPERM)
-   printf("/tmp must be not mounted noexec\n");
-  exit(1);
- }
- printf("OK\n");
- munmap(addr, UM_KERN_PAGE_SIZE);
-
- close(fd);
-}
+extern void check_tmpexec(void);
 
 void os_early_checks(void)
 {

-- 
Steve Ballmer: Innovation!  Inigo Montoya: You keep using that word.
I do not think it means what you think it means.


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Re: [uml-devel] [PATCH] uml: move TMP default from /tmp to /dev/shm.

[Rob Landley]

On Monday 28 November 2005 12:36, Jeff Dike wrote:
> On Mon, Nov 28, 2005 at 10:29:57AM -0600, Rob Landley wrote:
> > Signed-off-by: Rob Landley <rob@landley.net>
> >
> > UML really wants shared memory semantics form its physical memory map
> > file, and the place for that is /dev/shm.  So move the default, and fix
> > the error messages to recognize that this value can be overridden.
>
> This looks sort of OK, but what's with the whitespace mangling?

I sent a second copy that hopefully is less mangled.  Did it make it through 
ok?

Kmail is a "helpful" mail client.  It's possible to get it to send out 
unmangled patches, assuming you remember to set the moon phase and get the 
chicken entrails in the right position.  (I sometimes miss a step.)

>     Jeff

Rob
-- 
Steve Ballmer: Innovation!  Inigo Montoya: You keep using that word.
I do not think it means what you think it means.


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Re: [uml-devel] [PATCH] uml: move TMP default from /tmp to /dev/shm.

[Jeff Dike]

On Mon, Nov 28, 2005 at 10:29:57AM -0600, Rob Landley wrote:
> Signed-off-by: Rob Landley <rob@landley.net>
> 
> UML really wants shared memory semantics form its physical memory map file,
> and the place for that is /dev/shm.  So move the default, and fix the error
> messages to recognize that this value can be overridden.

This looks sort of OK, but what's with the whitespace mangling?

				Jeff


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Re: [uml-devel] [PATCH] uml: move TMP default from /tmp to /dev/shm.

[Henrik Nordstrom]

On Mon, 28 Nov 2005, Jeff Dike wrote:

> On Mon, Nov 28, 2005 at 11:52:15AM -0600, Rob Landley wrote:
>> I sent a second copy that hopefully is less mangled.  Did it make it through
>> ok?
>
> By eye, both looked the same.

Not entirely, the first not only munged the whitespace, it also 
word-wrapped the diff lines..

The second only munged the whitespace.

Sending patches as attachments is generally safer than inline when using 
GUI mail programs.

Regards
Henrik


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Re: [uml-devel] [PATCH] uml: move TMP default from /tmp to /dev/shm.

[Jeff Dike]

On Mon, Nov 28, 2005 at 11:52:15AM -0600, Rob Landley wrote:
> I sent a second copy that hopefully is less mangled.  Did it make it through 
> ok?

By eye, both looked the same.

> Kmail is a "helpful" mail client.  It's possible to get it to send out 
> unmangled patches, assuming you remember to set the moon phase and get the 
> chicken entrails in the right position.  (I sometimes miss a step.)

Why not cc yourself if you're not sure?

				Jeff


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Re: [uml-devel] [PATCH] uml: move TMP default from /tmp to /dev/shm.

[Rob Landley]

[-- Attachment #1: Type: text/plain, Size: 866 bytes --]

On Monday 28 November 2005 13:27, Henrik Nordstrom wrote:
> On Mon, 28 Nov 2005, Jeff Dike wrote:
> > On Mon, Nov 28, 2005 at 11:52:15AM -0600, Rob Landley wrote:
> >> I sent a second copy that hopefully is less mangled.  Did it make it
> >> through ok?
> >
> > By eye, both looked the same.
>
> Not entirely, the first not only munged the whitespace, it also
> word-wrapped the diff lines..
>
> The second only munged the whitespace.
>
> Sending patches as attachments is generally safer than inline when using
> GUI mail programs.

Inline is linux-kernel policy, but here the darn thing is as an attachment.  
(No, I seem to have no control whatsoever over the type of the attachment.  I 
have checkboxes for "compress, encrypt, and sign" though, in case I can't 
figure out how to do that to the actual file...)

I need to find a real mail client, it seems.

Rob

[-- Attachment #2: devshm.patch --]
[-- Type: text/x-diff, Size: 1906 bytes --]

diff -ur linux-2.6.15-rc2/arch/um-old/os-Linux/mem.c linux-2.6.15-rc2/arch/um/os-Linux/mem.c
--- linux-2.6.15-rc2/arch/um-old/os-Linux/mem.c	2005-11-23 02:35:49.000000000 -0600
+++ linux-2.6.15-rc2/arch/um/os-Linux/mem.c	2005-11-28 09:33:21.158395976 -0600
@@ -34,7 +34,7 @@
 			break;
 	}
 	if((dir == NULL) || (*dir == '\0'))
-		dir = "/tmp";
+		dir = "/dev/shm";
 
 	tempdir = malloc(strlen(dir) + 2);
 	if(tempdir == NULL){
@@ -159,3 +159,26 @@
 	}
 	return(fd);
 }
+
+
+void check_tmpexec(void)
+{
+	void *addr;
+	int err, fd = create_tmp_file(UM_KERN_PAGE_SIZE);
+
+	addr = mmap(NULL, UM_KERN_PAGE_SIZE,
+		    PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE, fd, 0);
+	printf("Checking PROT_EXEC mmap in %s...",tempdir);
+	fflush(stdout);
+	if(addr == MAP_FAILED){
+		err = errno;
+		perror("failed");
+		if(err == EPERM)
+			printf("%s must be not mounted noexec\n",tempdir);
+		exit(1);
+	}
+	printf("OK\n");
+	munmap(addr, UM_KERN_PAGE_SIZE);
+
+	close(fd);
+}
diff -ur linux-2.6.15-rc2/arch/um-old/os-Linux/start_up.c linux-2.6.15-rc2/arch/um/os-Linux/start_up.c
--- linux-2.6.15-rc2/arch/um-old/os-Linux/start_up.c	2005-11-23 02:35:49.000000000 -0600
+++ linux-2.6.15-rc2/arch/um/os-Linux/start_up.c	2005-11-28 09:41:04.051025600 -0600
@@ -296,29 +296,7 @@
 	check_sysemu();
 }
 
-extern int create_tmp_file(unsigned long long len);
-
-static void check_tmpexec(void)
-{
-	void *addr;
-	int err, fd = create_tmp_file(UM_KERN_PAGE_SIZE);
-
-	addr = mmap(NULL, UM_KERN_PAGE_SIZE,
-		    PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE, fd, 0);
-	printf("Checking PROT_EXEC mmap in /tmp...");
-	fflush(stdout);
-	if(addr == MAP_FAILED){
-		err = errno;
-		perror("failed");
-		if(err == EPERM)
-			printf("/tmp must be not mounted noexec\n");
-		exit(1);
-	}
-	printf("OK\n");
-	munmap(addr, UM_KERN_PAGE_SIZE);
-
-	close(fd);
-}
+extern void check_tmpexec(void);
 
 void os_early_checks(void)
 {

Re: [uml-devel] [PATCH] uml: move TMP default from /tmp to /dev/shm.

[Rob Landley]

On Monday 28 November 2005 14:05, Jeff Dike wrote:
> > Kmail is a "helpful" mail client.  It's possible to get it to send out
> > unmangled patches, assuming you remember to set the moon phase and get
> > the chicken entrails in the right position.  (I sometimes miss a step.)
>
> Why not cc yourself if you're not sure?

Because it seems to depend on things like whether or not I've adjusted my mail 
filters since the last reboot, and current moon phase, and that only tells me 
whether or not it worked after the fact of sending it?

>     Jeff

I think what broke it this time was turning on the .signature.  That seems to 
convert tabs to spaces throughout the entire message.  Nice and orthogonal.  
(Just like integrating kmail in and kontact was.  No unwanted behavior 
changes there...)

Sorry, I'll try sending mail with patches from the darn command line in 
future...

Rob
-- 
Steve Ballmer: Innovation!  Inigo Montoya: You keep using that word.
I do not think it means what you think it means.


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Re: [uml-devel] [PATCH] uml: move TMP default from /tmp to /dev/shm.

[Blaisorblade]

On Monday 28 November 2005 22:47, Rob Landley wrote:
> On Monday 28 November 2005 13:27, Henrik Nordstrom wrote:
> > On Mon, 28 Nov 2005, Jeff Dike wrote:
> > > On Mon, Nov 28, 2005 at 11:52:15AM -0600, Rob Landley wrote:

> Inline is linux-kernel policy, but here the darn thing is as an attachment.

They explicitly accept plain-text attachments when inline doesn't work. 
However, here we are *much* liberal, since we apply anyhow patches by hand, 
and plain-text attachment works as well when feeding the patch to patch on  
stdin, even if you feed it the whole mail. IIRC.

> (No, I seem to have no control whatsoever over the type of the attachment. 

> I have checkboxes for "compress, encrypt, and sign" though, in case I can't
> figure out how to do that to the actual file...)

Don't look at the mime type...

Right-click -> "properties" -> "encoding" (I guess) -> choose "7bit" or "8bit" 
over "base64". Btw, kmail never tried to send a patch as base64, it always 
chose 7bit, as in your patch.

> I need to find a real mail client, it seems.

-- 
Inform me of my mistakes, so I can keep imitating Homer Simpson's "Doh!".
Paolo Giarrusso, aka Blaisorblade (Skype ID "PaoloGiarrusso", ICQ 215621894)
http://www.user-mode-linux.org/~blaisorblade

		
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