Messages in this thread | | | Subject | Re: [PATCH ipmi/kcs_bmc v1] ipmi: kcs_bmc: optimize the data buffers allocation | From | "Wang, Haiyue" <> | Date | Sat, 7 Apr 2018 10:37:22 +0800 |
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On 2018-04-07 05:47, Corey Minyard wrote: > 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 > less. > I got this idea from another code review, but that patch allocates 30 more the same size memory block, reducing the devm_kmalloc call will be better. For KCS only have 3, may be the key point is memory waste.
> In the original case, you allocate three 1000 byte buffers, resulting > in 3 > 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 from book, 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 with performance, or something else.
BR. Haiyue
> -corey > >> Signed-off-by: Haiyue Wang <haiyue.wang@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 >> --- a/drivers/char/ipmi/kcs_bmc.c >> +++ b/drivers/char/ipmi/kcs_bmc.c >> @@ -435,6 +435,7 @@ static const struct file_operations kcs_bmc_fops = { >> struct kcs_bmc *kcs_bmc_alloc(struct device *dev, int sizeof_priv, >> u32 channel) >> { >> struct kcs_bmc *kcs_bmc; >> + void *buf; >> kcs_bmc = devm_kzalloc(dev, sizeof(*kcs_bmc) + sizeof_priv, >> GFP_KERNEL); >> if (!kcs_bmc) >> @@ -448,11 +449,12 @@ struct kcs_bmc *kcs_bmc_alloc(struct device >> *dev, int sizeof_priv, u32 channel) >> mutex_init(&kcs_bmc->mutex); >> init_waitqueue_head(&kcs_bmc->queue); >> - kcs_bmc->data_in = devm_kmalloc(dev, KCS_MSG_BUFSIZ, GFP_KERNEL); >> - 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) >> return NULL; >> + 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); > >
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