Re: [9fans] LPAE patch for ARM
On Sat, 4 Jun 2022, Richard Miller wrote: There's a new patch bcm-lpae which uses the 64-bit page table format to allow 32-bit ARM kernels to support more than 4GB of physical memory. At present this is mainly of interest for the 8GB Raspberry Pi 4, but there's nothing Pi-specific in the MMU code so it may have future application for bigger ARM systems. Thanks a lot Richard! -- 9fans: 9fans Permalink: https://9fans.topicbox.com/groups/9fans/T2b3e951db9f7c17f-Mc302193000a78af072a244de Delivery options: https://9fans.topicbox.com/groups/9fans/subscription
[9fans] little pipe speedtest
inspired by:
https://mazzo.li/posts/fast-pipes.html
I was curious to see how things stacked up on plan 9.
The machines are apples to oranges (my 9front box
is a 2015-ish era Zbox with a Intel Core i5-7300HQ
processor, and my work machine is a Linux with a
12 core Ryzen 9 3900X).
Transferring 128 gigs instead of the 10 in the initial
benchmark, here are the results:
# 9front 595684fd8a2f08e12d5df48152d93fb8ab800fe3 amd64
% time rc -c '6.write | 6.read'
0.33u 23.28s 11.64r rc -c 6.write | 6.read
# Linux 5.13.0-40-generic #45~20.04.1-Ubuntu SMP
$ time sh -c './write | ./read'
real0m32.039s
user0m0.231s
sys 0m34.576s
here's the plan 9 version of the program:
write.c:
#include
#include
void
main(void)
{
usize sz;
char* buf;
sz = 1 << 18;
buf = malloc(sz);
memset((void*)buf, 'X', sz);
while(1){
n = write(1, buf, sz) != sz)
break;
exits(nil);
}
read.c:
#include
#include
enum {
KiB = 1024ULL,
MiB = 1024*KiB,
GiB = 1024*MiB,
};
void
main(void)
{
vlong sz, r, n;
char* buf;
r = 0;
sz = 1 << 18;
buf = malloc(sz);
while(r <= 128ULL*GiB){
n = read(0, buf, sz);
if(n <= 0)
break;
r += n;
}
exits(nil);
}
And the linux version:
write.c:
#include
#include
#include
int
main(int argc, char **argv)
{
size_t sz;
char* buf;
sz = 1 << 18;
buf = malloc(sz);
memset(buf, 'X', sz);
while(1)
if(write(1, buf, sz) != sz)
break;
return 0;
}
read.c:
#include
#include
enum {
KiB = 1024ULL,
MiB = 1024*KiB,
GiB = 1024*MiB,
};
int
main(int argc, char **argv)
{
ssize_t sz, r, n;
char* buf;
r = 0;
sz = 1 << 18;
buf = malloc(sz);
while(r <= 128ULL*GiB){
n = read(0, buf, sz);
if(n <= 0)
break;
r += n;
}
return 0;
}
--
9fans: 9fans
Permalink:
https://9fans.topicbox.com/groups/9fans/Td13d120eca9d5ee7-M40cecbefc1f455f5c2c25358
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[9fans] LPAE patch for ARM
There's a new patch bcm-lpae which uses the 64-bit page table format to allow 32-bit ARM kernels to support more than 4GB of physical memory. At present this is mainly of interest for the 8GB Raspberry Pi 4, but there's nothing Pi-specific in the MMU code so it may have future application for bigger ARM systems. The LPAE page table format works on the Pi 2 and Pi 3 as well, where it may provide a wee performance improvement from simpler page fault handling. When building a bcm kernel, the choice of page descriptor format is determined by putting either 'mmu' or 'mmu64' in the 'misc' section of the config file. The patch has been applied in the current 9legacy SD card image for Raspberry Pi on http://9legacy.org/download.html, and also in the 9pi SD card image on http://9p.io/sources/contrib/miller (though nowadays for all practical purposes I recommend 9legacy as a better choice). If you just want to update the kernel, source is in http://9p.io/sources/contrib/miller/9/bcm as usual. -- 9fans: 9fans Permalink: https://9fans.topicbox.com/groups/9fans/T2b3e951db9f7c17f-Mbacd4cfcb29eca6dadc2a77a Delivery options: https://9fans.topicbox.com/groups/9fans/subscription
