Re: [PATCH]mmap: improve scalability for updating vm_committed_as

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Thu, 2011-03-31 at 10:34 +0800, Andrew Morton wrote:
> On Thu, 31 Mar 2011 08:56:43 +0800 Shaohua Li <shaohua.li@xxxxxxxxx> wrote:
> 
> > > This is a big change, and it wasn't even changelogged.  It's
> > > potentially a tremendous increase in the expense of a read from
> > > /proc/meminfo, which is a file that lots of tools will be polling. 
> > > Many of those tools we don't even know about or have access to.
> > Assume we don't read /proc/meminfo too often.
> 
> That's a poor assumption.  top(1) and vmstat(8) read it, for a start. 
> There will be zillions of locally-developed monitoring tools which read
> meminfo.
> 
> Now, it could be that something under meminfo reads _already_ does a
> massive walk across all CPUs.  If so then we'll have already trained
> people to avoid reading /proc/meminfo and this change might be
> acceptable.
> 
> But if this isn't the case then it's quite likely that this change will
> hurt some people quite a lot.  And, unfortunately, the sort of people
> who we will hurt tend to be people who don't run our stuff until a long
> time (years) after we wrote it.  By which time it's going to be quite
> expensive to get a fix down the chain and into their hands.
Just looked at the code. nr_blockdev_pages() of si_meminfo iterate all
block devices. For people who care about the time, their system must
have more block devices than CPUs. so this isn't a big issue?

Thanks,
Shaohua

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxxx  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>


[Index of Archives]     [Linux ARM Kernel]     [Linux ARM]     [Linux Omap]     [Fedora ARM]     [IETF Annouce]     [Bugtraq]     [Linux]     [Linux OMAP]     [Linux MIPS]     [ECOS]     [Asterisk Internet PBX]     [Linux API]