lkml.org 
[lkml]   [2010]   [Apr]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] - New round-robin rotor for SLAB allocations
On Mon, 26 Apr 2010 16:00:41 -0500
Jack Steiner <steiner@sgi.com> wrote:

> We have observed several workloads running on multi-node systems where
> memory is assigned unevenly across the nodes in the system. There are
> numerous reasons for this but one is the round-robin rotor in
> cpuset_mem_spread_node().
>
> For example, a simple test that writes a multi-page file will allocate pages
> on nodes 0 2 4 6 ... Odd nodes are skipped. (Sometimes it allocates on
> odd nodes & skips even nodes).
>
> An example is shown below. The program "lfile" writes a file consisting of
> 10 pages. The program then mmaps the file & uses get_mempolicy(...,
> MPOL_F_NODE) to determine the nodes where the file pages were allocated.
> The output is shown below:
>
> # ./lfile
> allocated on nodes: 2 4 6 0 1 2 6 0 2
>
>
>
> There is a single rotor that is used for allocating both file pages & slab
> pages. Writing the file allocates both a data page & a slab page
> (buffer_head). This advances the RR rotor 2 nodes for each page
> allocated.
>
> A quick confirmation seems to confirm this is the cause of the uneven
> allocation:
>
> # echo 0 >/dev/cpuset/memory_spread_slab
> # ./lfile
> allocated on nodes: 6 7 8 9 0 1 2 3 4 5
>
>
> This patch introduces a second rotor that is used for slab allocations.
>
> include/linux/cpuset.h | 6 ++++++
> include/linux/sched.h | 1 +
> kernel/cpuset.c | 20 ++++++++++++++++----
> mm/slab.c | 2 +-
> 4 files changed, 24 insertions(+), 5 deletions(-)

Why no update to slob and slub?


\
 
 \ /
  Last update: 2010-04-30 22:55    [W:0.052 / U:0.116 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site