The Performance Impact of CONFIG_DEBUG_KERNEL

< CONFIG_CC_OPTIMIZE_FOR_SIZE=y
< CONFIG_KALLSYMS_ALL=y
< CONFIG_KPROBES=y
< CONFIG_KRETPROBES=y

< # CONFIG_DEFAULT_DEADLINE is not set
< CONFIG_DEFAULT_CFQ=y
< CONFIG_DEFAULT_IOSCHED="cfq"

< # CONFIG_PREEMPT_NONE is not set
< CONFIG_PREEMPT_VOLUNTARY=y

< CONFIG_ENABLE_WARN_DEPRECATED=y
< CONFIG_MAGIC_SYSRQ=y
< CONFIG_UNUSED_SYMBOLS=y

< CONFIG_DEBUG_KERNEL=y
< CONFIG_DETECT_SOFTLOCKUP=y
< CONFIG_TIMER_STATS=y
< CONFIG_DEBUG_STACKOVERFLOW=y
< # many config_debug settings
< # have been removed from this list

> # changing the optimization had minimal effect
> # CONFIG_CC_OPTIMIZE_FOR_SIZE is not set
> # CONFIG_KPROBES is not set

> # changing I/O scheduler had no effect
> CONFIG_DEFAULT_DEADLINE=y
> # CONFIG_DEFAULT_CFQ is not set
> CONFIG_DEFAULT_IOSCHED="deadline"


> # changing preemption had no effect
> CONFIG_PREEMPT_NONE=y
> # CONFIG_PREEMPT_VOLUNTARY is not set

> # CONFIG_ENABLE_WARN_DEPRECATED is not set
> # CONFIG_MAGIC_SYSRQ is not set
> # CONFIG_UNUSED_SYMBOLS is not set

> # removing all kernel debugging and hacking
> # had a huge effect on performance
> # CONFIG_DEBUG_KERNEL is not set

//set start time
time(&starttime);
    
//encrypt buffer 1 million times with the same key
for(i=0; i < 1000000; i++){
    //perform aes-256-CBC on 512 bytes at a time using the same iv
    for(aes_cbcoffset=0;aes_cbcoffset<bufsize/512;aes_cbcoffset++){
        memcpy(aes_ivec,aes_ivec2,AES_BLOCK_SIZE);
        AES_cbc_encrypt(buf+aes_cbcoffset*512,buf+aes_cbcoffset*512,
	512,&(aes_encryptionkeyschedule),aes_ivec,AES_ENCRYPT);
    }
}

//print first char of cyphertext version
printf("buf: %c\n",buf[0]);

//decrypt buffer 1 million times with the same key
for(i=0; i < 1000000; i++){
    //perform aes-256-CBC on 512 bytes at a time using the same iv
    for(aes_cbcoffset=0;aes_cbcoffset<bufsize/512;aes_cbcoffset++){
        memcpy(aes_ivec,aes_ivec2,AES_BLOCK_SIZE);
        AES_cbc_encrypt(buf+aes_cbcoffset*512,buf+aes_cbcoffset*512,
	512,&(aes_decryptionkeyschedule),aes_ivec,AES_DECRYPT);
    }
}

//print plaintext version, which matches the original
printf("buf: %s\n",buf);

//determine end time and calculate stats
time(&endtime);
printf("elapsed: %d\n",endtime-starttime);
printf("MB/s: %d\n",(2*bufsize)/(endtime-starttime));

//set start time
starttime = current_kernel_time();
    
//encrypt buffer 1 million times with the same key
for(i=0; i < 1000000; i++){
    //perform aes-256-CBC on 512 bytes at a time using the same iv
    for(aes_cbcoffset=0;aes_cbcoffset<bufsize/512;aes_cbcoffset++){
        memcpy(aes_ivec,aes_ivec2,AES_BLOCK_SIZE);
        AES_cbc_encrypt(buf+aes_cbcoffset*512,buf+aes_cbcoffset*512,
	512,&(aes_encryptionkeyschedule),aes_ivec,AES_ENCRYPT);
    }
    if(i%1000==0) schedule();//don't hog the cpu
}

//print first char of cyphertext version
printk("buf: %c\n",buf[0]);

//decrypt buffer 1 million times with the same key
for(i=0; i < 1000000; i++){
    //perform aes-256-CBC on 512 bytes at a time using the same iv
    for(aes_cbcoffset=0;aes_cbcoffset<bufsize/512;aes_cbcoffset++){
        memcpy(aes_ivec,aes_ivec2,AES_BLOCK_SIZE);
        AES_cbc_encrypt(buf+aes_cbcoffset*512,buf+aes_cbcoffset*512,
	512,&(aes_decryptionkeyschedule),aes_ivec,AES_DECRYPT);
    }
    if(i%1000==0) schedule();//don't hog the cpu
}

//print plaintext version, which matches the original
printk("buf: %s\n",buf);

//determine end time and calculate stats
endtime = current_kernel_time();
printk("elapsed: %d\n",endtime.tv_sec-starttime.tv_sec);
printk("MB/s: %d\n",(2*bufsize)/(endtime.tv_sec-starttime.tv_sec));