The patch titled
SLAB: use num_possible_cpus() in enable_cpucache()
has been removed from the -mm tree. Its filename was
slab-use-num_possible_cpus-in-enable_cpucache.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
Subject: SLAB: use num_possible_cpus() in enable_cpucache()
From: Eric Dumazet <dada1@xxxxxxxxxxxxx>
The existing comment in mm/slab.c is *perfect*, so I reproduce it :
/*
* CPU bound tasks (e.g. network routing) can exhibit cpu bound
* allocation behaviour: Most allocs on one cpu, most free operations
* on another cpu. For these cases, an efficient object passing between
* cpus is necessary. This is provided by a shared array. The array
* replaces Bonwick's magazine layer.
* On uniprocessor, it's functionally equivalent (but less efficient)
* to a larger limit. Thus disabled by default.
*/
As most shiped linux kernels are now compiled with CONFIG_SMP, there is no way
a preprocessor #if can detect if the machine is UP or SMP. Better to use
num_possible_cpus().
This means on UP we allocate a 'size=0 shared array', to be more efficient.
Another patch can later avoid the allocations of 'empty shared arrays', to
save some memory.
Signed-off-by: Eric Dumazet <dada1@xxxxxxxxxxxxx>
Acked-by: Pekka Enberg <penberg@xxxxxxxxxxxxxx>
Acked-by: Christoph Lameter <clameter@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/slab.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)
diff -puN mm/slab.c~slab-use-num_possible_cpus-in-enable_cpucache mm/slab.c
--- a/mm/slab.c~slab-use-num_possible_cpus-in-enable_cpucache
+++ a/mm/slab.c
@@ -4033,10 +4033,8 @@ static int enable_cpucache(struct kmem_c
* to a larger limit. Thus disabled by default.
*/
shared = 0;
-#ifdef CONFIG_SMP
- if (cachep->buffer_size <= PAGE_SIZE)
+ if (cachep->buffer_size <= PAGE_SIZE && num_possible_cpus() > 1)
shared = 8;
-#endif
#if DEBUG
/*
_
Patches currently in -mm which might be from dada1@xxxxxxxxxxxxx are
origin.patch
optimize-timespec_trunc.patch
procfs-reorder-struct-pid_dentry-to-save-space-on-64bit-archs-and-constify-them.patch
vfs-delay-the-dentry-name-generation-on-sockets-and.patch
getrusage-fill-ru_inblock-and-ru_oublock-fields-if-possible.patch
time-smp-friendly-alignment-of-struct-clocksource.patch
ignore-stolen-time-in-the-softlockup-watchdog.patch
splice-and-readahead-interaction.patch
make-static-counters-in-new_inode-and-iunique-be-32-bits.patch
speedup-divides-by-cpu_power-in-scheduler.patch
futex-new-private-futexes.patch
lguest-the-host-code-vs-futex-new-private-futexes.patch
-
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