Re: reiser4 resize

[David Masover <ninja@slaphack.com>]

Alexey Polyakov wrote:
> On 9/20/06, £ukasz Mierzwa <prymitive@pcserwis.net> wrote:
> 
>> It's been proven that flushes are doing much more job then they should.
>> Not so long ago someone send a trace of block device io accesess during
>> reiser4 work and someone anylized it and said that some files or parts of
>> file where written over and over 200 times or so.

Wow.  I should go back and read that -- I assume this is being worked on?

>> a few months old filesystem that had been used often just shows a week
>> spot in reiser4, while downloading files with azureus with only 64KB of
>> data per second I got disk lid on almost all the time, swithcing to
>> rtorrent helped as it does not seem to call fsync ( I think I disabled
>> fsync in azureus).

Hmm, strange.  I am using Azureus, but I don't think it's fsync.  I can 
try rtorrent, but there are several things I like about Azureus that 
nothing else seems to do yet.

But also, Azureus didn't always do this.  In fact, I used it for several 
months before I started having this problem.

> Ah, I see, if bittorrent calls fsync often, it's no wonder that
> reiser4 behaves badly. I had to preload libnosync for some of my
> programs that do fsync to avoid this.

Way ahead of you.  I noticed how much fsync performance sucked when 
using vim, and I was sick of waiting 10 seconds every time I hit :w -- a 
LOT of stuff can pile up in 2 gigs of disk buffer, and at the time, 
Reiser4 fsync effectively just called sync.

I didn't know about libnosync (or it didn't exist yet, or didn't work, 
I'm not entirely sure), so I was faced with either patching vim, which 
had just been patched to _add_ fsync'ing, not to mention all the other 
programs that might fsync too much;  patching glibc (huge, I don't 
update it often, and I'd have no idea where to start);  or patching the 
kernel.

I now keep backups, and I maintain and apply the following (STUPID, 
DON'T TRY THIS AT HOME) patch to my kernel:

--- linux/fs/buffer.c   2006-08-15 20:40:36.504608696 -0500
+++ linux/fs/buffer.c.new       2006-08-15 20:42:35.877461264 -0500
@@ -366,12 +366,12 @@

  asmlinkage long sys_fsync(unsigned int fd)
  {
-       return __do_fsync(fd, 0);
+       return 0;
  }

  asmlinkage long sys_fdatasync(unsigned int fd)
  {
-       return __do_fsync(fd, 1);
+       return 0;
  }

  /*