Since IPMI 2.0 just defined minimum, no maximum:
KCS/SMIC Input : Required: 40 bytes IPMI Message, minimum
KCS/SMIC Output : Required: 38 bytes IPMI Message, minimum
We can enlarge the block size for avoiding waste, and make our driver
support most worst message size case. And I think this patch make checking
simple (from 3 to 1), and the code clean, this is the biggest reason I
change. The TLB is just memory management study from book, no data to
support access improvement. :)
On 2018-04-07 10:37, Wang, Haiyue wrote:
On 2018-04-07 05:47, Corey Minyard wrote:
I got this idea from another code review, but that patch allocates 30
the same size memory block, reducing the devm_kmalloc call will be
On 03/15/2018 07:20 AM, Haiyue Wang wrote:
Allocate a continuous memory block for the three KCS data buffers with
related index assignment.
I'm finally getting to this.
Is there a reason you want to do this? In general, it's better to
not try to
outsmart your base system. Depending on the memory allocator, in this
case, you might actually use more memory. You probably won't use any
For KCS only have 3, may be the key point is memory waste.
In the original case, you allocate three 1000 byte buffers, resulting
1024 byte slab allocated.
In the changed case, you will allocate a 3000 byte buffer, resulting in
a single 4096 byte slab allocation, wasting 1024 more bytes of memory.
As the kcs has memory copy between in/out/kbuffer, put them in the same
page will be better ? Such as the same TLB ? (Well, I just got this
no real experience of memory accessing performance. And also, I was told
that using space to save the time. :-)).
Just my stupid thinking. I'm OK to drop this patch if it doesn't help
performance, or something else.
Signed-off-by: Haiyue Wang <haiyue.w...@linux.intel.com>
drivers/char/ipmi/kcs_bmc.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/drivers/char/ipmi/kcs_bmc.c b/drivers/char/ipmi/kcs_bmc.c
index fbfc05e..dc19c0d 100644
@@ -435,6 +435,7 @@ static const struct file_operations kcs_bmc_fops
struct kcs_bmc *kcs_bmc_alloc(struct device *dev, int sizeof_priv,
struct kcs_bmc *kcs_bmc;
+ void *buf;
kcs_bmc = devm_kzalloc(dev, sizeof(*kcs_bmc) + sizeof_priv,
@@ -448,11 +449,12 @@ struct kcs_bmc *kcs_bmc_alloc(struct device
*dev, int sizeof_priv, u32 channel)
- kcs_bmc->data_in = devm_kmalloc(dev, KCS_MSG_BUFSIZ,
- kcs_bmc->data_out = devm_kmalloc(dev, KCS_MSG_BUFSIZ, GFP_KERNEL);
- kcs_bmc->kbuffer = devm_kmalloc(dev, KCS_MSG_BUFSIZ, GFP_KERNEL);
- if (!kcs_bmc->data_in || !kcs_bmc->data_out || !kcs_bmc->kbuffer)
+ buf = devm_kmalloc_array(dev, 3, KCS_MSG_BUFSIZ, GFP_KERNEL);
+ if (!buf)
+ kcs_bmc->data_in = buf;
+ kcs_bmc->data_out = buf + KCS_MSG_BUFSIZ;
+ kcs_bmc->kbuffer = buf + KCS_MSG_BUFSIZ * 2;
kcs_bmc->miscdev.minor = MISC_DYNAMIC_MINOR;
kcs_bmc->miscdev.name = dev_name(dev);