The patch titled Subject: fs: only send IPI to invalidate LRU BH when needed has been added to the -mm tree. Its filename is fs-only-send-ipi-to-invalidate-lru-bh-when-needed.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Gilad Ben-Yossef <gilad@xxxxxxxxxxxxx> Subject: fs: only send IPI to invalidate LRU BH when needed In several code paths, such as when unmounting a file system (but not only) we send an IPI to ask each cpu to invalidate its local LRU BHs. For multi-cores systems that have many cpus that may not have any LRU BH because they are idle or because they have not performed any file system accesses since last invalidation (e.g. CPU crunching on high perfomance computing nodes that write results to shared memory or only using filesystems that do not use the bh layer.) This can lead to loss of performance each time someone switches the KVM (the virtual keyboard and screen type, not the hypervisor) if it has a USB storage stuck in. This patch attempts to only send an IPI to cpus that have LRU BH. Signed-off-by: Gilad Ben-Yossef <gilad@xxxxxxxxxxxxx> Acked-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/buffer.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff -puN fs/buffer.c~fs-only-send-ipi-to-invalidate-lru-bh-when-needed fs/buffer.c --- a/fs/buffer.c~fs-only-send-ipi-to-invalidate-lru-bh-when-needed +++ a/fs/buffer.c @@ -1384,10 +1384,23 @@ static void invalidate_bh_lru(void *arg) } put_cpu_var(bh_lrus); } + +static bool has_bh_in_lru(int cpu, void *dummy) +{ + struct bh_lru *b = per_cpu_ptr(&bh_lrus, cpu); + int i; + for (i = 0; i < BH_LRU_SIZE; i++) { + if (b->bhs[i]) + return 1; + } + + return 0; +} + void invalidate_bh_lrus(void) { - on_each_cpu(invalidate_bh_lru, NULL, 1); + on_each_cpu_cond(has_bh_in_lru, invalidate_bh_lru, NULL, 1, GFP_KERNEL); } EXPORT_SYMBOL_GPL(invalidate_bh_lrus); _ Subject: Subject: fs: only send IPI to invalidate LRU BH when needed Patches currently in -mm which might be from gilad@xxxxxxxxxxxxx are smp-introduce-a-generic-on_each_cpu_mask-function.patch arm-move-arm-over-to-generic-on_each_cpu_mask.patch tile-move-tile-to-use-generic-on_each_cpu_mask.patch smp-add-func-to-ipi-cpus-based-on-parameter-func.patch smp-add-func-to-ipi-cpus-based-on-parameter-func-fix.patch slub-only-ipi-cpus-that-have-per-cpu-obj-to-flush.patch fs-only-send-ipi-to-invalidate-lru-bh-when-needed.patch mm-only-ipi-cpus-to-drain-local-pages-if-they-exist.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html