Re: nfs unhappiness with memory pressure

From: Trond Myklebust
Date: Mon Dec 05 2005 - 15:12:46 EST


On Mon, 2005-12-05 at 10:01 -0800, Kenny Simpson wrote:
> Tested with rc5 - same results. It was suggested that I run slabtop when the system freezed, so
> here is that info: (again, by hand, I'm getting another machine to use either netconsole or a
> serial cable).
>
> Active / Total Objects (% used) : 478764 / 485383 (98.6%)
> Active / Total Slabs (% used) : 14618 / 14635 (99.9%)
> Active / Total Caches (% used) : 79 / 138 (57.2%)
> Active / Total Size (% used) : 56663.79K / 57566.41K (98.4%)
> Minimum / Average / Maximum Object : 0.01K / 0.12K / 128.00K
>
> OBJS ACTIVE USE OBJ SIZE SLABS OBJ/SLAB CACHE SIZE NAME
> 403088 403088 100% 0.06K 6832 59 27328K nfs_page
> 30380 30380 100% 0.50K 4340 7 17360K nfs_write_data
> 15134 15134 100% 0.27K 1081 14 4324K radix_tree_node
> ...
>
>
> The other thing is that the stack trace showsd slabtop as being halted in throttle_vm_writeout
> while allocating memory, and the writetest was halted waiting to allocate memory.

Can somebody VM-savvy please explain how on earth they expect something
like throttle_vm_writeout() to make progress? Shouldn't that thing at
the very least be kicking pdflush every time it loops?

Cheers,
Trond

> I'll get more detailed stack traces once I get the second machine set up.
>
> -Kenny
>
>
>
>
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