[Geany] do not open oversize files

[Krzysztof Żelechowski]

Dnia środa, 5 stycznia 2011 o 20:14:00 Dimitar Zhekov napisał(a):
> On Wed, 5 Jan 2011 11:08:18 +1100
> Lex Trotman <elextr at gmail.com> wrote:
> 
> > And on modern kernels virtual memory can be overcommitted
> > significantly so it may not work
> 
> I haven't said that a successful alloc guarantees everything will be
> fine. :) But with the kernel defaults, you'll at least catch the most
> obvious cases.
> 
> > is expensive since the page tables have to be constructed even if
> > the memory is not used.
> 
> CPU cost: that's only once per file, memory cost: < 1%
> 
> > Also this could cause fragmentation of the virtual address space that
> > may limit how many times it will work.
> 
> Yes, or some other problems. It's a hack, and should only be used if
> we can't agree on anything better. Personally I'm for a preference.
> 
> ---
> 
> On Tue, 4 Jan 2011 22:05:52 +0100
> Krzysztof Żelechowski <giecrilj at stegny.2a.pl> wrote:
> 
> > > > I do not know where you got it from, but the last OS I know that
> > > > behaved like that was MacOS 7. [cut]
> > > 
> > > Like what?..
> > 
> > Like necessarily allocating a contiguous block of physical memory.
> 
> What a strange idea... Unless your CPU lacks MMU, of course.
> 
> > GNU malloc uses mmap so it is all virtual.
> 
> mmap for large blocks and heap for small blocks IIRC, and naturally, the
> heap itself is mmap-ed.
> 
> > > If by "01 << 040" you mean 4GB, how much real and virtual memory do
> > > you have?
> > > 
> > > 
> > 
> > I have 1 GB of physical memory.  (01 << 040) is the first integer that does not fit into unsigned int.
> 
> So then, using more than 4GB _will_ be a problem on your system, QED.
> I pointed out it's a rough check.
> 
> But if your malloc() fails on 4GB, and not below that, you either have
> an unusually large swap file, or your kernel is set to always

procs -----------memory---------- ---swap-- -----io---- -system-- -----cpu------
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa st
 1  0 324092  35424  17904 283900    7   38   191    77  479  810 16  5 76  3  0

MemTotal:        1004948 kB
SwapTotal:       1510040 kB
VmallocTotal:   34359738367 kB
VmallocChunk:   34359546964 kB

Filename                                Type            Size    Used    Priority
/dev/sda5                               partition       1510040 276772  -1

> overcommit. With the defaults, the check works much better.

overcommit_memory = 0
overcommit_ratio = 50
CommitLimit:     2012512 kB

vmalloc is not set in /proc/cmdline.

I think this setup is quite typical.

Chris